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UNITED STATES DEPARTMENT OF AGRICULTURE

BUREAU OF PUBLIC ROADS

APPROACH TO OBSERVATION STATION ON MAINE HIGHWAY TRANSPORTATION SURVEY

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1926

PUBLIC ROADS

A JOURNAL OF HIGHWAY RESEARCH
U. S. DEPARTMENT OF AGRICULTURE

BUREAU OF PUBLIC ROADS

CERTIFICATE: By direction of the Secretary of Agriculture, the matter contained herein is published as administrative information and is required

VOL. 6, NO. 3

for the proper transaction of the public business

MAY, 1925 H. S. FAIRBANK, Editor

TABLE OF CONTENTS

The Maine Highway Transportation Survey
A Preliminary Report

The Wagon and the Elevating Grader . :
Part II.—The Influence of Design on Elevating Grader Costs

THE U. S. BUREAU OF PUBLIC ROADS
Willard Building, Washington, D. C.

REGIONAL HEADQUARTERS,
Bay Building, San Francisco, Calif.

DISTRICT OFFICES

DISTRICT No. 1, Oregon, Washington, Montana, and Alaska.
Box 3900, Portland, Oreg.

DISTRICT No. 2, California and Nevada.
Bay Building, San Francisco, Calif.

DISTRICT No. 3, Colorado and Wyoming.
301 Customhouse Building, Denver, Colo.

DISTRICT No. 4, Minnesota, North Dakota, South Dakota, and Wisconsin.

410 Hamm Building, St. Paul, Minn.

DISTRICT No. 5, Iowa, Kansas, Missouri, and Nebraska.

8th Floor, Saunders-Kennedy Bldg., Omaha, Nebr.

DISTRICT No. 6, Arkansas, Louisiana, Oklahoma, and Texas.
1912 F. & M. Bank Building, Fort Worth, Tex.

DISTRICT No. 7, Illinois, Indiana, Kentucky, and Michigan.
South Chicago Station, Chicago, Ill.

DISTRICT No. 8, Alabama, Georgia, Florida, Mississippi, South Carolina,

and Tennessee.
Box J, Montgomery, Ala.

DISTRICT No. 9, Connecticut, Maine, Massachusetts, New Hampshire,
New Jersey, New York, Rhode Island, and Vermont.
Federal Building, Troy, N. Y.

DISTRICT No. 10, Delaware, Maryland, North Carolina, Ohio,
Pennsylvania, Virginia, and West Virginia.
Willard Building, Washington, D. C.

DISTRICT No. 12, Idaho and Utah.
Fred J. Kiesel Building, Ogden, Utah.

DISTRICT No. 13, Arizona and New Mexico.
242 West Washington St., Phoenix, Anz.

Owing to the necessarily limited edition of this publication it will be impossible to distribute it free to any persons or
institutions other than State and county officials actually engaged in planning or constructing public highways, instructors
in highway engineering, periodicals upon an exchange basis, and Members of both Houses of Congress. Others desiring
to obtain “Public Roads’ can do so by sending 10 cents for a single number or $1 per year to the Superintendent of Docu-
ments, Government Printing Office, Washington, D. C

THE MAINE HIGHWAY TRANSPORTATION SURVEY

A PRELIMINARY REPORT

BY THE DIVISION OF HIGHWAY TRANSPORT AND ECONOMICS, U. S. BUREAU OF PUBLIC ROADS
Reported by J. G. McKAY, Chief of Division, and O. M. ELVEHJEM, Highway Economist

PRELIMINARY analysis of the evidence ob-
tained in the Maine highway transportation
survey, conducted by the United States Bureau

of Public Roads in cooperation with the Maine State
Highway Commission has developed a number of
interesting and useful facts with regard to the traffic
on the Maine highways, its growth over a period of
years, present distribution over the State system,
probable future density, and other matters of interest
generally to all concerned with the planning and con-
struction of highways. The evidence analyzed was
recorded in the course of the field study which was
begun July. 1, 1924, and lasted until October 31, 1924.

The rapid increase in the demand for highway service
is indicated by the increase in motor vehicle registra-
tion and in the traffic on the State highway system
from 1916 to 1924. Between 1916 and 1920 the regis-
tration doubled, it doubled again from 1920 to 1924,
and it is estimated that it will double again from 1924
to 1930. Parelleling this increase, the traffic doubled
between 1916 and 1919, it doubled again from 1919 to
1923, and it is estimated that it will double again in
the period from 1924 to 1930. But while the demand
for highway service in the State, considering the trans-
portation of passengers and commodities together, has
thus apparently doubled and redoubled in the past
eight years, consideration of the motor-truck and
passenger-car traffic separately suggests that there is a
difference, so far as the State highway system is con-
cerned, in the demands for motor-truck and passenger-
car transportation. This is evidenced by the fact that
truck traffic has increased at a slower rate than truck
registration, while passenger-car traffic has increased
at a faster rate than passenger-car registration; but,
for total vehicles, the rates of increase of highwa
traffic and vehicle registration have been nearly equal.

One of the most valuable results of the survey is the
collection of data upon which future traffic may be
forecast with reasonable accuracy. This makes pos-
sible the development of a definite program of future
improvement by determining the routes to be improved,
the order of their improvement, and the type of im-
provement required. The forecast of future traffic is
of particular value in Maine since the State has reached
the second critical stage in the development of its high-
ways. Hitherto the highway commission has wisely
constructed large mileages of gravel roads to make
accessible the greatest possible area of the State with
the funds available.

The concentration of motor-vehicle traffic around
the centers of population on the principal State roads
now makes necessary a definite improvement policy
governing the selection of the routes to be recon-
structed with surfaces of higher-type, and the deter-
mination of the type of surfacing. The Maine experi-
ence indicates that a gravel road will not successfully
carry over 500 vehicles per 12-hour day without resort-
ing to surface treatment.

Application of the most reliable available informa-
tion with regard to the savings in operating costs of
vehicles made possible by improvement in road sur-
faces indicates that, on the basis of present traffic, the

45029—25},——1

300 miles of most heavily traveled roads in the State
could be improved from an earth-road condition to a
condition in which every mile would be surfaced with
concrete, and the entire cost of the improvement, with
interest at 4 per cent, would be repaid by the savings
in operating costs of passenger cars only in slightly over
four years.

SEVEN PER CENT OF THE ROADS SERVE
TRAFFIC

MORE THAN HALF THE

The survey has brought to light a number of in-
teresting facts with regard to the traffic on the roads
of the State. For example, it is shown that the primary
highway system which embraces only 7.1 per cent of
the total highway mileage carries 53.4 per cent of the
total daily vehicle mileage. Furthermore, 18.4 per
cent of the primary system carries 38.7 per cent of the
total daily vehicle mileage on the system. From this
it follows that, with respect to the entire highway sys-
tem of the State, 1.3 per cent of the total mileage
serves more than a fifth of the traffic, as measured in
vehicle miles.

It is evident that the heavy concentration of traffic
is confined to a relatively small percentage of the total
highway mileage. For this reason it is advocated that
traffic zones should be created to bring together for
construction and maintenance purposes those sections
of the highway system which serve approximately the
same amount and type of traffic.

The traffic importance of the primary system as
compared with the secondary system appears even
greater when considered from the point of view of
motor-truck traffic than when considered from the
standpoint of passenger-car traffic. Practically all
trucks using the Maine highways have capacities
between one-half and 2% tons, and the number of
trucks of 5 tons capacity or over is practically negli-
gible. Over 80 per cent of the trucks observed were
equipped with pneumatic tires, and from 55 to 67 per
cent were loaded. Wheel loads in excess of 2,500
pounds were found to be very exceptional on trucks
weighing less than 6,000 pounds gross, and the maxi-
mum wheel load for trucks of less than 12,000 pounds
gross weight (3 tons capacity) was found to be 5,000
pounds. Over 98 per cent of such trucks, however,
aes wheel loads less than 4,500 pounds.

On a vehicle-mileage basis it is found that a con-
siderable portion of the cost of providing highway
service on the primary system is due to its use by
foreign vehicles. But these vehicles pay into the State
treasury through the gasoline tax a sum which the State
would not receive if there were no gasoline tax, and
the amount of the tax paid is proportional to their use |
of the system. The use of the State’s roads by foreign
motor trucks is much less extensive than its use by
foreign passenger cars and, except near the State
line and on a few major highways, is negligible.

As a result of the survey a forecast traffic map has
been prepared which shows the anticipated density
of traffic on roads of the State’s primary and secondary
systems between July and November, 1930. Neglect-
ing such factors as the effect of major mechanical im-
provements of automobiles, it is believed that the

(45)

actual traffic in 1930 will closely approximate the
estimated traffic as recorded on this map, and the map
has therefore been used as a basis for a number of
detailed suggestions with regard to the program of
highway improvement up to 1930.

TRAFFIC ON PRIMARY, SECONDARY, AND THIRD-CLASS HIGHWAYS

There are 23,104 miles of highway in the State. Of
this mileage 1,630 miles, constituting the State high-
way system, is defined as the primary system. State-
aid highways, consisting of 4,049 miles not included in
the State highway system but serving as feeders to it,
are defined as the secondary system. Third-class
roads, comprising 17,425 miles, include all highways not
included in the State or State-aid systems.!

This classification of the roads, it was one of the
purposes of the survey to check by a more exact
determination of the traffic served by them. At the
same time the survey methods were designed to supply
the information needed to decide upon the adequacy
of the types of surfaces laid on roads of the three
systems with respect to present and probable future
traffic, and to serve as a paces for the equitable parti-
tion of funds available for construction and main-
tenance.

To serve these purposes it was necessary that the

survey supply four general classes of data, as follows::

(1) Density of traffic on all parts of each system; (2)
the size and loading of motor truck traffic; (8) vehicle-
mileage per year on each of the three systems; and,
(4) the probable growth of traffic over a reasonable
future period.

The traffic classification of roads and the selection of
the most suitable type of highway surface to serve
traffic depends upon the type of traffic units as well
as the number of these units. The more important
considerations are: (1) Density of present and future
total traffic; (2) the ratio of trucks to total vehicles; (3)
the proportion of trucks of large, medium, and small
capacity, and the resulting gross loads; (4) the maxi-
mum wheel loads; and, (5) the frequency of critical
gross loads and wheel loads. In individual cases other
factors must also be considered, but in general the
more important considerations are those above men-
tioned. ‘The final selection of type of highway surface
depends upon certain physical considerations, such as
availability and cost of materials, as well as upon
traffic considerations.

Vehicle mileage involving, as it does, the factors of
number of vehicles and mileage traveled serves as the
basis for the equitable allocation of funds in propor-
tion to the utilization of the three systems; and the
extension of the curves of traffic and vehicle registra-
tion makes possible a forecast of the growth of traffic
which will enable those in charge of highway adminis-
tration to make the necessary provision for future
maintenance and construction.

Density of traffic on the three systems.—The density
of traffic,’ which is one of the criteria determining the

1 Chap. 25, Sec. 5, Laws of Maine, 1917.

2 In this report certain terms, frequently used, have invariably the same meaning.
‘These terms and their definitions are as follows:

Vehicles refers only to motor vehicles (passenger cars and trucks) exclusive of
horse-drawn conveyances.

Traffic is defined as the movement to and fro of vehicles over a highway.

Density of traffic is defined as the number of motor vehicles passing any given point
on a highway in a unit of time. Unless a different unit of time is specifically stated
it refers to the number of vehicles passing any given point on a highway during a day
of 24 hours.

Daily refers to a day of 24 hours.

Vehicle-mile is defined as the movement of a vehicle 1 mile.

Vehicle-miles per mile is defined as the sum of the mileage traveled by all motor
vehicles in passing over 1 mile of highway. Itis numerically equivalent to the average
density of traffic on the mile of highway.

classification of roads and the types of surface needed,
has been computed from the number of vehicles passing
each of the survey stations during the observation
periods corrected for each station to a 24-hour day.’

Computed in this way the average density of traffic
on the three systems, as now designated, is shown in
Table 1. Considering each of the systems as a whole
the table indicates that the average density of traffic
on the primary system is thirty-six times as great as
on the third-class system and over four times as great
as on the secondary system; and, as shown in Table 2,
this same relation apples approximately to the truck
and passenger-car traffic separately as well as to the
total traffic, from which it follows, also, that the
relative. density of motor-truck and passenger-car
traffic on the three systems is approximately the same,
the ratio in each case being about 1 to 10.

TABLE 1.—Average density of traffic on the primary, secondary,
and third-class highway systems, July 1 to October 31, 1924

Index of
relative
density
of traffic
(third
class=
100 per
cent)

Average
density

Highway system
of traffic

Vehicles
per day | Per cent

Primary: (16380 :mii1es) es 22 ees eee ee eee Se eee 1,044 3, 600
Secondary-(4,049 miles) foe ee ee eee ee ee ee ees 244 840
‘Ehird:class (7442600 es)) eee: ee aa eee eee eee eee eer 29 100

TABLE 2.—Average density of motor-truck and passenger-car traffic
on the primary, secondary, and third-class highway systems,
July 1 to October 31, 1924

Other things being equal, these indices describe the
relative average highway requirements of the traffic
on the three systems and govern the average expendi-
tures which may justifiably be made for the improve-
ment of each mile of each system. ‘Thus, if the ratios
of motor trucks to passenger cars is approximately the
same, the fact that the average density of traffic on the
primary system is thirty-six times as great as the aver-
age density on the third-class system means that the
average justifiable expenditure for the improvement of
each mile of the primary system is thirty-six times as
great as the average expenditure which can be justified
for each mile of the third-class system.

Traffic served by the three systems.—These indices also
indicate the relative transportation service afforded by
each mile of the three systems, but by reason of the
different extent of the systems they do not describe

3 The accuracy of the determination of density of traffic is influenced by the dis-
tance between the survey stations. Exactness of method would require a density
record for each point on the highway system where traffic varies. The cost involved
in proportion to the relatively small gain in accuracy does not justify the location of
recording stations at close intervals. The density computed for each station on the
ene erat system is applied to sections of the system reasonably adjacent to
each station.

the relative magnitude of the service rendered by the
systems or their relative total utilization considered as

arts of the whole system of the State. This can only

e described in terms of the total daily vehicle mileage
on the three systems, which is the sum of the distances
traveled in a day by all vehicles on each system.‘

The importance of distinguishing between the total
vehicle mileage on each system and the average density
of traffic on each (which is numerically equivalent to
the vehicle mileage per mile) is clearly indicated in
Table 3. For, while the average density or vehicle
mileage per mile on the primary system is thirty-six
times the average density on the third-class system,
Table 3 shows that the total traffic service rendered by
the primary system, of 1,630 miles, as measured in
vehicle-miles, is three and one-half times as great as
the total traffic service rendered by the 17,425 miles
of the third-class system. The latter relation should
control the apportionment of available funds to the
three systems; the former should control the justifiable
expenditure per mile on each system.

TABLE 3.—Relative traffic service of the primary, secondary, and
third-class highway systems

Portion Daily of total daily
length ot) hgteny| istic | Saby | trattlo
Highway system & Sway service poe service
| system | mileage by each | Sebyice (third
in each iis rendered Abee=
| system y by each | 409 ner
| system cent)
| =~ = Se eee ee
Vehicle
Miles Per cent miles | Per cent | Per cent
[plane ayes ee eee | 1, 6380 ad, 1, 702, 000 | 53. 4 340
POCOMMALV Resets kate loka 8 | 4, 049 17.5 | 986, 000 | 30.9 197
MEGsClasss fe 8 ey | 17,425 75.4 499, 000 | ae 100
} | |

The importance of the primary system to motor-
vehicle users is evident from the fact that 53.4 per cent
of the total daily vehicle mileage on all highways in
Maine is found on the primary system, which includes
only 7.1 per cent of the total highway mileage. The
shght traffic importance of the third-class system is
evidenced by the fact that only 15.7 per cent of the
total daily vehicle mileage is found on this system,
which includes 75.4 per cent of the total highway
mileage.

In these analyses of the relations between the three
systems in Maine it must be borne in mind that the re-
lations both as to density of traffic and daily vehicle
mileage depend upon two elements which restrict their
application more or less closely to the existing situation
in Maine. These elements are the existing density of

4 The daily vehicle mileage on any system is the product of the total number of
vehicles operated over any part of the system during the day and the average trip
mileage of those vehicles. But the total number of vehicles operated over any part
of the system during the day is the sum of the densities observed at the stations on
the system divided by the number of times each vehicle is counted. With any given
number of stations the number of times each vehicle is counted is equal to the average
trip mileage divided by the average distance between stations; e. g., if the average
trip is 35 miles and the average distance between counting points is 1 mile, each
vehicle will be counted on the average 35 times. : bats

The mathematical derivation of the approximate method of computing vehicle

mileage is as follows: ct , ‘ Q
Dail hiel il _ (Sum of densities) (Average trip mileage)
any velicle mleage= umber of times each vehicle is counted
(Sum of densities) (Average trip mileage)
= Average trip mileage _

Average distance between stations
= (Sum of densities) (Average distance between stations)

2 .,,_., Highway mileage
= (Sum of densities) Number of stations

Sum of densities . :
Number of stations 1s>way mileage)
= (Average density) (Highway mileage)

traffic on each mile of the Maine highways and the
mileage of the three systems. Obviously, the expan-
sion of the primary system by including 1,000 miles of
highway now a part of the secondary system would
materially change the relative daily vehicle mileage on
the two systems. Similarly, a change in the mileage
included in each system would also affect the average
density of traffic on the three systems. The primary
system, in general, now includes the more important
highways of the State; the inclusion of a considerable
mileage of less important highways would result in
lowering the average density of traflic on the system.

It is evident, therefore, that the relationships be-
tween the three systems are true only for these systems
as they exist to-day, and that any change in the systems
will modify the relationships; and they are applicable
in other States only in so far as the factors producing
highway traffic and the proportion of highway mileage
in the several systems of such States is comparable with
the existing conditions in Maine.

Moreover, these relationships apply only to the three
systems in Maine considered as units. Analysis of
the traffic on the roads included in the sytems shows
that there are material differences in the traffic im-
portance of roads within each system.

COMPARISON OF TRAFFIC eid Ae SECTIONS OF THE PRIMARY
YST

In Table 4 traffic is analyzed on three sections of the
primary system. Section | includes route 1, from Kit-
tery to Belfast; route 20, from Brunswick to Fairfield;
route 100, from Portland to Augusta; and route 196,
from Brunswick to Auburn—a total of 300 miles.
Section 2 includes route 1, Ellsworth to St. Stephan;
route 15, Oldtown to Houlton; route 20, Fairfield to
the north State line; and route 24, from Houlton to the
north State line—a total of 467 miles. All other
routes of the primary system are grouped under sec-
tion 3.

TasLe 4.—Highway mileage and traffic on three sections of the
primary system

From this analysis it will be seen that the average
density of traffic on 300 miles of the primary system
(section 1) is over four times as great as the average
density on section 2, which includes 467 miles and over
twice as great as the average density on the 863 miles
which compose section 3. The entire primary system,
which includes 7.1 per cent of the total highway mile-
age, serves 53.4 per cent of the total daily traffic in
vehicle-miles. But 300 miles, or 18.4 per cent of the
primary system, serves 38.7 per cent of the total traffic
served by the 1,630 miles of the primary system.
With respect to the entire highway system of the State
these 300 miles constitute on 1.3 per cent of the total
highway mileage, but they serve 20.7 per cent of the
total traffic.

The importance of section 1 is further illustrated by
the comparison of the average daily gross tonnage per
mile moved over each of the three sections of the
primary system, which is shown in Table 5.

TABLE 5.—Average daily gross tonnage per mile moved over three
sections of the primary system

Average daily gross tonnage
per mile
Section No. aie een ae
Passen- | Motor r
ger cars | trucks Total
ase |

This table shows that in point of tonnage per mile,
as well as density of traffic, section 1 of the primary
system is over four times as important as section 2
and over twice as important as section 3.

Still another indication of the importance of the
principal roads of the primary system is presented by
Table 6, which shows the average maximum density
of traffic on certain roads, as observed on panes dur-
ing the period of the traffic survey, July 1 to October
a1, 1924.

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Fia. 1.—Average density of all motor-vehicle traffic on principal primary and sec-
ondary highways in Maine, July 1 to October 81, 1924

Taste 6.—Average maximum density of traffic on certain roads of
the primary system (observed_on Sundays during the period July
1 to October 31, 1924)

Average maximum density
of traffic (Sunday)
Route and location of station ee
Motor | Passen-
trucks | ger cars Total
Vehicles | Vehicles | Vehicles
Route 1: per day | per day | per day
South of Portland te. === ae aes Soe eee 213 | 9, 781 9, 994
Stateline (south) jes eee eee 68 6, 780 6, 848
North of Portland 2s sates ae eee ee eee 98 5, 367 5, 465
West of Brunswick____--- ae, 70 | 3, 673 38, 743
Southwest of Rockland __ 87 2, 695 2, 782
Route 20, north of Winslow _- 122 4, 357 4,479
Route 100, west of Augusta__- 82 3, 285 3, 367
Route 196:
Southeast of Auburn_-- Jats 77 2, 335 2, 412
INorthsol Bruns wi Ck ese. eee ee eee 55 | 5, 182 5, 187

A recapitulation of all data indicating the utiliza-
tion of the highways of the three systems is given in
Table 7.

TaBLE 7.—Motor-vehicle utilization of Maine highways, July 1 to
October 31, 1924

All high- Primary Secondary | Third-class
ways system system system
Highway mileage__________- 23, 104 1, 630 4, 049 17, 425
Percentage of highway mile-
ARGe = Koh ee a Ce 100.0 | Vou 17.5 75. 4
Daily vehicle-miles: |
All vehiclestasussete ses 3, 187, 000 | 1, 702, 000 986, 000 499, 000
Passenger cars_....-.---- 2, 904, 000 1, 548, 000 893, 000 463, 000
GMail aya Gang ON! 283, 000 154, 000 93, 000 36, 000
Average density of traffic:!
(Aulinvehiclesuaseseaeeee 138 1, 044 244 29
Passenger cars__......-- 126 950 221 27
ED TUCKS See San = saan 12 94 23 2
Total vehicle-miles, July 1
to Oct. 31, 1924:
Auli eli clesaaees ats eee 392, 001,000 | 209, 346,000 | 121,278,000 | 61,377,000
Passenger cars---.._---- 357, 192,000 | 190, 404,000 | 109, 839,000 | 56, 949, 000
RrUcks Sale eee 34, 809, 000 18, 942, 000 11, 439, 000 4, 428, 000
Percentage of vehicle miles: |
Aliviehiclesies-.==—s ee 100. 0 53. 4 30. 9 15.7
Passenger cars. -..-.--=- | 100. 0 53. 3 30. 8 15.9
TUCKS oe eerie see 100. 0 54. 4 32.9 12) 7
Average daily gross tons
per mile:
AWivehicles: 2 = 22 en 201 T, 621 356 42
Passenger cars__--..-_-- 176 1, 330 309 38
URTUCKS Ses. see ees 25 191 47 4

1 The average density of traffic is the weighted average density per day reduced to
the nearest whole number. These average values were obtained by weighting the
average daily number of vehicles at each station, or group of similar stations, by the

number of miles of highway on which the daily traffic was approximately equal to °

this average, and therefore approximates the exact average obtained by summing the
vehicles per day on each mile of highway and dividing the total by the number of
miles of highway. ;

RELATIVE TRAFFIC IMPORTANCE OF PRINCIPAL ROADS

The relative traffic importance of the principal roads
of the Maine highway system, as determined by the
average density of traffic, is shown clearly in Figure 1,
in which the density of traffic on roads of the primary
and secondary systems is represented by the width
of the lines. The chart shows at a glance which roads
require the largest outlay of construction funds to
provide adequate highway service.

The greatest density of traffic is found near the
centers of population—Portland, Auburn, Lewiston,
Augusta, Brunswick, Waterville, Bangor—and the
summer-resort. district. Clearly the 300 miles pre-
viously defined as section 1 of the primary system con-
stitute the backbone of the entire system. These roads
from Kittery to Belfast, from Brunswick to Fairfield,
from Portland to Augusta, via Auburn, and from
Brunswick to Auburn have, markedly, a greater den-
sity of traffic than any others in the State.

Excluding ©

these and the roads from Fairfield to Bangor and from
Bangor to Ellsworth and Oldtown, the average den-
sity of traffic on the balance of the Maine highway
system will not exceed 1,000 vehicles per day. ,

On a considerable mileage of the primary system and
a large mileage of the secondary system the average
density of traffic was less than 300 vehicles per day
during the four months of the survey. It is anticipated
that the density on these routes will not exceed 600
vehicles per day by 1930. No large expenditures will
be required for high-type improvements on these roads
for some years. They should receive only a sufficient
amount of the construction and maintenance funds
each year to meet their actual traffic needs, and
the major portion of such funds should be devoted
to ae immediate improvement of the heavy-traffic
roads.

Clearly, there is need for the creation of traffic zones
bringing together for construction and maintenance
purposes those sections of the highway system which
serve approximately the same amount and type of traffic
and to distinguish between those routes which require
constant supervision and policing to insure satisfactory
service and safety to traffic and those which do not.

In the main it is evident that the primary system
includes the principal traffic arteries of the State and is
therefore well selected. On the basis of their traffic
density, however, some roads now included in the
secondary system could more properly be included in
the primary system than some that are included. The
roads which could well be transferred to the primary
system are those from Wells to Sanford, from Portland
to Standish, from Auburn to Mechanic Falls, and from
Oakland to Norridgewock.

The density of motor-truck traffic on the principal
roads of the primary and secondary systems is shown
in Figure 2. Obviously, the principal motor-truck
routes in the State are those from Kittery to Portland,
Portland to Augusta via Auburn, Portland to Bruns-
wick, Lisbon Falls to Auburn, Auburn to Mechanic
Falls, Waterville to Fairfield, Thomaston to Camden,
Bangor to Ellsworth, Bangor to Oldtown, and Port-
land to Naples.

In general it will be recognized that these routes
which have the largest daily motor-truck traffic are,
with few exceptions, identical with those which have
the greatest density of total traffic. The link of the
primary system from Houlton to Van Buren via Easton
and Presque Isle shows a relatively higher proportion
of trucks to total traffic than is to be found on the pri-
mary system as a whole. So, also, does the route from
Bangor to Ellsworth, a highway urgently in need of
improvement. The motor-truck capacity analysis of
the road from Portland to Naples, which also shows a
heavy proportion of trucks to total traffic, indicates that
this road carries an unusually large proportion of the
heavier trucks.

_ The general use of motor trucks on the principal
traffic routes indicates the need for highway improve-
ment of a type adequate to provide service for truck
traffic. The fact that the highway between Bruns-
wick and Waldoboro is surfaced with gravel may be, in
part, responsible for the small density of, motor-truck
traffic on this route. But the chart of motor-truck
traffic density confirms the conclusion drawn from the
discussion of the density of total traffic that high-type
improvement of a considerable mileage of the primary

and a large mileage of the secondary system can safely
be deferred for some years.

Sections of the secondary system which have a con-
siderable density of truck traffic are the roads from
Portland to Standish and from Auburn to Mechanic
Falls. These roads were shown to be eligible for trans-
fer to the primary system by the analysis of total traffic.

STATUS OF ROAD IMPROVEMENT IN RELATION TO TRAFFIC DENSITY

The free flow of traffic on the principal sections of the
primary system is hindered by gaps of unimproved
highways or sections surfaced with gravel. Between
Kittery and Portland, as shown in Figures 3 and 4,

RANGELEY

FARMINGTON
52

LI} 400 TRUCKS —@IODEFOR

PRIMARY ROAD - SOLID BLACK
SECONDARY ROAD-OPEN SPACE

gg hitreRY
Fic. 2.—Average density of truck traffic on principal primary and secondary high-
ways in Maine, July 1 to October 31, 1924

there are sections of concrete, macadam, and gravel.
Sections of gravel road on a heavy-traffic route such as
this do not provide adequate service to traffic and the
yearly maintenance costs are excessive.

Between Auburn and Augusta, on one of the most
heavily traveled routes in the State, approximately 16
of the 31 miles are gravel. Between Fennemich and
Belfast there is a large mileage of gravel that undoubt-
edly does not give satisfactory service to the dense
traffic. Between Brunswick and Augusta, also, there
are sections of macadam, gravel, and unimproved road.
After improvement the density of traffic over this
route can be expected to increase materially.

The routes from Bangor to Ellsworth, one direct and
the other via Orland, iulustrate the need of improve-
ment in proportion to the density of traffic. The direct
route is gravel, although it is an important trucking

The daily variation in the number of horse-drawn
conveyances was found to be much greater than the
variation in motor vehicles. At different stations the
proportion of horse-drawn traffic to total traffic varies

route and is also of considerable importance as a pas-

from less than 1 to 20 per cent. In general the greatest
senger-car route. On the Bangor-Orland-Ellsworth

density of horse-drawn traffic was recorded at the
stations at which the motor-vehicle traffic was light,
although heavy horse-drawn traffic was found at some
heavy motor-vehicle traffic stations which were located
near towns. Extremely light horse-drawn traffic was
found at some of the outlying stations which are
located in undeveloped sections of the State.

| The heaviest proportion of horse-drawn traffic was
|

7 te
/ A
7 !

i anal)
He N Saatoe \FORT KENT

/ Ns

es L/ observed at stations located in well-developed agri-
: Prsan see] | cultural areas which are off the main lines of motor-
vehicle travel and which therefore have little motor-
vehicle traffic. The horse-drawn traffic during Sep-
tember and October was considerably higher at the
majority of stations than it was during the months
of July and August. This increase was undoubtedly
due to the crop marketing movement during the early
fall months.

‘ \ ‘ x or
Ni 4 yi ‘f ie Sy
an, x © GREENVILLE oS Bog \ of
- > "4 B ee * ToPsFIELoY § ‘
al ? SS f Se vA
: ee Va /
Q . CALAIS) y Af
QRANGELEY } ip renay G i
5 e
)\ i fi & f) |
UPTON \ an a a !
fe rami : rie es /
Vo, LIVERMORE re, ¥ ( we a = Ps \ 2
| \ “ALLS : 2 ecurss Se Lp c Parca
EE ’ 2D ie Ry q “FF ISUND FALLS |
J \
a) (
99 (2 }
) (
i C ve A
1 : \ ~ ne:
¢ n i a — y \
% 2 : \ / oo)
%, oe is %, 9 GREENVILLE f \
Cc y & Or) ; d» TOPSFIELD)
| ca , 4 ’
We My y te
f G B
~ GORHAM | v) a
IRTLAND |
=
4 aa = 5000 VEHICLES | VERS
ee ‘
h LEGEND oe | Xs
HE concrete | Ln
FES] MACADAM jqurton eas oe
GRAVEL \ SAX
[3] UNIMPROVET
[__] secompary

Fic. 3.—Average density of motor vehicle traffic and road types on the primary sys-
tem of Maine

route there is large unimproved mileage. The pas-
senger-car movement and the surprisingly large motor-
truck traffic over a large part of the route justifies at
least a gravel surface.

In the northern part of the State the heavy trucking

is caused largely by the transportation of potatoes. | oc Aeon RES k ,
The average density of motor-truck traffic in this part a a “nu
of the State exceeds that on a large mileage of the pri- ‘ff b ~~ Ofronruno
mary system in the southeastern part of the State and | ge [__] |=400 rrucrs

Fair teny . — pine Fone

apparently justifies a higher type of highway.

LEGEND
WRG concrete
EEBB macapam
GRAVEL
[=] unimproveo
3

Fia. 4.—Average density of motor-truck traffic and road types on the primary system of
Maine

MOTOR-BUS AND HORSE-DRAWN TRAFFIC

Motor-bus traffic was recorded at very few stations,
and even on the routes on which busses were operated
their number was negligible.

SECONDARY

ANALYSIS OF MOTOR-TRUCK CAPACITY AND WHEEL LOADS

Motor trucks in use on the Maine highway system
are predominantly of the smaller capacities, from
one-half to 144 tons. Even on the heavily traveled
sections of the primary system practically all the
trucks fall within the capacity group of one-half to
21% tons, as shown by Table 8.

TABLE 8.—Motor-truck capacities on the primary system

|
Section 1 |

Table 9 presents a summary, in greater detail, of
the percentages of trucks of the various capacities
observed at each weight station.

TaBLe 9.—Summary of the distribution of loaded trucks by
capacity groups at weight stations

| Distribution by capacity groups

Station | l

| 42 to 144 2to 244 | 3to4 | 5to5% | 6to7%

| tons tons tons tons tons

| Per cent | Per cent | Per cent | Per cent | Per cent
11) eee Berne oe oe Ss | 87. 5. 5 VERE | Sea cpee 5 ealeee se oe ra
UUVAn= Sea) a pe ee eee 89. 7.6 OT Al eremee aoa eee ees
GS) oat. Se ee ee ere 93. 9 5.9 PYG Cee eyelet aes So
A) eee Se Rees Se 86.8 10.3 gO | Ree Senn eee ee ae
LU 9 a) nt ie | 95.0 3h YF ila 0% 2h Bee
AG oo SRE es ee ee 84, 3 12.3 2.8 {Oja<- pee ee
AN) socers Rote te ee | 78.3 13.0 12 once eee
HOS rt ee ed 81.6 12.7 4.9 35) ie ee ee
AOR ose ne ak 86. 6 10.0 hil <0) ecm ee
OS wy 358 Rae ae eee 89.3 9.4 OD brs Le Feel ERE ne
“ilo 2 Mpa ot A ae a se a | 82.3 13.1 3.0 .5 eal
CBD = | at ee ee ae 92.1 1.4 5.8 a fal aa es
(OR) oS 88 nats a 93.1 6. 4 SRN see oe el ee ee
EI 2 eens? bie Pa ee ee Sa 86.6 10.8 2.5 Sle) eee ee
Ae eee ree LOO}(0 3 |e seen | eee eo eee 1h ae eee ee
I psa ie ee Se ee 87.5 LDPE (eae = or IC Bes Cae ee See
HON = «co eacepeh Ry ee | 85.9 10.0 EL |e ee renee es | ne eee I
(VAs) 2) 2 Se ee ee ee eee 81.5 10.9 (UR oes eae Re eee ee
i) ee SA nee oes oe aes | 92.4 4.8 QB) (areas a elles ore Os
(UD = 350 ee ee re | 91.5 4.0 ONE ee oa ee

At every weight station but one (station 407) more
than 80 per cent of the truck traffic consists of trucks
of less than 2 tons capacity. At 7 of the 20 stations
over 90 per cent of the traffic is composed of trucks of
less than 2 tons capacity. Five-ton trucks are found
at only 8 of the 20 stations, and the highest proportion
of 5-ton trucks at any station is 1.5 per cent (station
407). Trucks larger than the 5 to 5% ton group are
found at only one station (station 421), and this is
undoubtedly an exceptional movement. At allstations
over 90 per cent of the truck traffic is made up of trucks
of less than 3 tons capacity. Station 406, although
having a smaller percentage of large trucks than some
of the other stations, actually has a larger number of
heavy trucks per day than does any other station.
For use in the control of design of pavement to meet
traffic requirements these percentages should be applied
to the average daily truck density.

Except at stations 407 and 408 over 90 per cent of the
loaded trucks at all weight stations were under 12,000
pounds gross weight. Trucks weighing over 24,000
pounds gross were found at only two stations (stations
407 and 408), and the percentages of such trucks at
these stations was very small, 0.3 per cent at station
407 and 0.1 per cent at station 408. Trucks weighing
between 12,000 pounds and 18,000 pounds gross were

found at 11 of the 20 stations, but the highest per-
centage of such trucks at any station was 3.4 per cent
(station 407). The percentage of loaded trucks
weighing less than 12,000 pounds gross agrees quite
closely with the percentage of trucks of less than 3
tons capacity, as shown in Table 10.

TABLE 10.—Comparison of the percentages of trucks under 8 tons
capacity and under 12,000 pounds gross load by stations

| |]
Trucks || Trucks
oe | epee _ Trucks under
‘ | under | 12,000 ren under 12,000
Station 3tons | pounds | Station | 3tons | pounds
capacity gross | capacity gross
weight | weight
| Percent | Per cent Per cent | Per cent
401___ | 92. 6 93.6 || 421_ 95. 4 | 96. 5
A) De ee ene 97.3 95. 5 || 422_ 93. 5 95. 0
403 eae 99.8 98.3 || 423_ 99. 5 99. 5
404___ 97.1 96.0 || 424_ 97.4 97.2
405 scae seers 98. 7 98.9 || 425_ 100. 0 100. 0
406_ 96. 6 OSes WAGs ey ee oes see 100. 0 99. 6
A Tie Sie ae oe 91.3 | EVAN hz by feta US MT Seay 95.9 95.8
AOR ES ee eee tert 94.3 SONOMA 28 cater Le aes oe 92. 4 100. 0
400 2 te ees 96. 6 95. 5 || 470 ee ee 97.2 99. 5
410° Sa ee | 98. 7 Oonon | 450 eae sae, oe 95. 5 100. 0

A comparison of the percentages in Table 10 indi-
cates that for roads in Maine where truck traffic con-
sists exclusively of trucks of less than 3 tons capacity
it is fairly safe to select a type of pavement which will
carry a maximum load of 12,000 pounds.

Over 80 per cent of the trucks on Maine highways
are equipped with pneumatic tires. Practically all
trucks weighing less than 6,000 pounds gross are so
equipped, and although the percentage of pneumatic-
tired trucks weighing between 6,000 and 12,000 pounds
gross varies considerably with location it will average
approximately 75 per cent of the total.

The observations indicate that the maximum wheel
load of trucks whose gross load is under 6,000 pounds
is 3,000 pounds, that wheel loads over 2,500 pounds are
very exceptional, and that 95.9 per cent of the trucks
under 6,000 pounds gross weight have rear-wheel
loads of less than 2,000 pounds. For gross loads of
less than 12,000 pounds 5,000-pound wheel loads are
the maximum, and of all gross loads less than 12,000
pounds 98.5 per cent have wheel loads of less than
4,500 pounds.

PROPORTION OF LOADED TRUCKS OVER 50 PER CENT

The ratio of loaded to total trucks varies from
54.8 to 66.6 per cent. The lowest percentage is found
at station 425 and the highest at station 401. Of the
four stations at which less than 60 per cent of the
trucks observed were loaded three are located on out-
lying routes—station 425 near Columbia Falls, station
423 south of Mattawamkeag, and station 402 east of
Rumford. The fourth, station 403, is on route 100 be-
tween Auburn and Augusta.

The average net weight per loaded truck varies
from 760 pounds at station 405 to 2,060 pounds at
station 407, and the average gross weight from 3,420
pounds at station 425 to 6,180 pounds at station 407.
Only two stations, 407 and 408, have an average net
weight in excess of 1,600 pounds per loaded truck.
These are also the only stations that show an average
gross weight in excess of 5,000 pounds per loaded
truck. Several of the stations of relatively heavy
traffic density show very low avapee net and gross
weights per loaded truck because of the ea i:
of one-half-ton trucks. This is especially true of sta-

tion 406, which has a larger number of 3 to 4 ton
trucks and also a larger number of 5-ton trucks per
day than stations 407 or 408, but because of the large
number of small trucks the average weights are low.
The average trip mileage per vehicle depends very
largely upon the location of the station. Stations 407,
410, 421, and 425 show average trip mileages in excess
of 35 miles; stations 402, 403, and 429 show average
trip mileages below 20 miles.

USE OF MAINE HIGHWAYS BY FOREIGN MOTOR VEHICLES

When it is considered that 21.4 per cent of all motor
vehicles on the primary system are of foreign registra-
tion, that the foreign vehicles account for an average
density of traffic on the primary system amounting
to 223 vehicles a day, and that these vehicles travel
each day 364,000 vehicle-miles, it becomes evident
that the cost of providing and maintaining adequate
highways in Maine is increased by the usage of the
roads by foreign vehicles.

Foreign passenger cars constitute 21.2 per cent of
all motor vehicles on the primary system. They pro-
duce 23.3 per cent of the total passenger car-miles
on the primary system, 9.9 per cent on the secondary
system, and 6.5 per cent on the third-class system. ~

Foreign motor trucks are of much less importance.
They account for only 2.1 per cent of the motor-
truck-miles on the primary system, 1.6 per cent on the
secondary system, and on the third-class system their
influence is negligible.

Detailed data on the use of the Maine highways by
foreign vehicles are given in Tables 11, 12, and 13.

Foreign passenger cars form a very important part
of the total passenger-car traffic at stations near the
State line and also at points a considerable distance
from the State line on the principal traffic routes. As
distance from the State line increases the proportion of
foreign passenger cars decreases. On route 1 near
Kittery (station 407), 68.2 per cent of the passenger
cars carry foreign licenses. Near Wells (station 1B)
the percentage is 43.5, and south of Portland the per-
centage is 34.5 (Table 14). North of Portland foreign
passenger cars decrease to 29.2 per cent on route 1 (sta-
tion 409) and 18.1 per cent on route 18 (station 408).

On route 1 the percentage of foreign passenger cars
near Bath (station 405) is 27.6 per cent and near Rock-
land (station 429) 18.2 per cent. On route 20, south
of Augusta (station 430), foreign passenger cars are
19.1 per cent of the total traffic.

Other routes in the State do not carry as large a pro-
portion, but some foreign passenger cars were found at
every station located on the primary and secondary
system.

Trucks of foreign registration are of less importance.
Foreign trucks make up over 10 per cent of the total
truck traffic at only four stations, and these are all
located near the State line. Only three stations (sta-
tions 406, 407 and 1B) show an average of more than
10 foreign trucks a day; only seven have an average of
more than five foreign trucks a day; and a large num-
ber of stations have no foreign truck traffic. The differ-
ence in importance of foreign trucks and foreign passen-
ger cars is indicated in Table 14, which presents data for
three stations on route 1, south of Portland.

The comparative use of the Maine highway system
by Maine and foreign vehicles is further evidenced by
the average mileage of Maine and foreign passenger

TasLe 11.—Utilization of Maine highway systems by all Maine
and foreign motor vehicles

: Total
Percent- a) ae Daily vehicle-
age of ot traffic vehicle- giles by,
. : : State *! miles by tate an
System Registration | and for- oak State and | foreign
eign ve- BP K foreign vehicles,
hicles | “rice | Vehicles | July 1 to
oD Oct. 31, 1924
Vehicles Vehicle- Vehicle-
Per cent | par day miles miles
Primaryss <ss2- see Maine_-____- 78.6 821 | 1,338,000 | 164, 546, 000
ee ee ee ee Foreign ____- 21.4 223 364, 000 | 44, 800, 000
Total sates & Ree alee ele 100. 0 1, 044 1, 702, 000 | 209, 346, 000
Secondary-..--_..-..-- | Maine--___-- 91.0 222 897, 000 | 110, 363, 000
1) O23 ae eee | Foreign _-___- 9.0 22 89,000 | 10, 915, 000
TOCA. ae oe ee ee 100. 0 244 986, 000 | 121, 278, 000
Third class.....-------- Maine_--__- amass 27 471,000 | 57,879, 000
1) OS 22 ea ere aren | Foreign --_-- 5.7 2 28, 000 3, 498, 000
Total somes Se Ya i nie Rs 100. 0 29 499,000 | 61,377, 000
i}

TaBLe 12.—Utilization of Maine highway systems by Maine and
foreign passenger cars

Total
Percent- Wi Daily vehicle-
age of of tra ffie eos ae Pe
ae s ‘ State area ill pach (c ions tate an
System Registration | and for- tie State and | foreign
eign ve- erences foreign vehicles,
hicles “a jee vehicles July 1 to
c Oct. 31, 1924
Vehicles Vehicle- Vehicle-
Per cent | per day miles miles
Primary ses =e area Maines. sae 76.7 729 | 1,187,000 | 146, 040, 000
DO. se ee oe Foreign ____- 23.3 221 361,000 | 44, 364, 000
Motalacasa=S2 ose ess. aa eee 100. 0 950 1, 548, 000 | 190, 404, 000
Secondary__.--..-.._-.- Maine. —..-- 90. 1 199 805, 000 | 98, 965, 000
Dott. Seas 2 ae MOLelgn ase 9.9 22 88, 000 | 10,874, 000
Total ze eae St A ee eee 100. 0 221 | 893, 000 | 109, 839, 000
Third class.......-.---- Maine_____- 93.5 25| 433,000| 53, 247, 000
foe ar See a cars Foreign ____- 6.5 2 30, 000 3, 702, 000
0) fs ee Sell mee ee 5 so! 100. 0 27 463,000 | 56, 949, 000

TaBLe 13.—Utilization of Maine highway systems by Maine and
foreign motor trucks

Total
Percent- oe | Daily vehicle-
age of of traffic Lh iioae ae by
Ley es pcre State ’|! miles by ate an
System Registration and for- ee State and foreign
eign Ve- | Gion ve- foreign vehicles,
hicles hi Alec, vehicles July 1 to
Oct. 31, 1924
Vehicles Vehicle- Vehicle-
. Per cent | per day miles miles
Primanyone eer Maines =---- 97.9 92 150,800 | 18, 544, 000
D0 eee ee SEAS Foreign ____- 2 2 3, 200 398, 000
Totalcetse: Sones Bene 2 eee 100.0 | 94 154,000 | 18, 942, 000
Secondary..--------_--- | Maine_____- 98.4| 226 91,500 | 11, 256, 000
Do ete ae Foreign. ___- 1.6 i} 1, 500 183, 000
Trotalie aaa ee oe. Ja. eee 100.0| 23.0 —- 93,000 | 11, 439, 000
Thirdiclass 2aeeeess Se eats Leweee 100. 0 2 36, 000 4, 428, 000
eee ae AB ee ES | Foreign tac oes 428 |i So See eee eee 2 ee
Tolalatete 3 ee pee 100. 0 2 36, 000 4, 428, 000

cars. Maine passenger cars average 36 miles per vehicle
per trip on the primary system and 26 miles per vehicle
per trip on the secondary system. Foreign passenger
cars average 97 miles per vehicle per trip on the primary
system and 73 miles per vehicle per trip on the sec-
ondary system.

TABLE 14.—Foreign passenger cars and trucks on route 1 , south
of Portland

a ae eect Foreign trucks
Station | Location
| Percent- | ap hi Percent- ge cha
age | y age EN
number number
AQ Vee ots. 68.2 | 2, 540 12.8 | 17.3 | Near State line at Kittery.
Ite ee ae 43.5 | 1,197 6.5 | 17.9 | Near Wells, half way from
State line to Portland.
AUG Ree 5S 34.5 | 1, 854 2.7 | 11.5 | Near Portland.

GASOLINE-TAX REVENUES

All motor vehicles using the Maine highways con-
tribute toward the upkeep of these highways through
the payment of a gasoline tax of 1 cent per gallon on
all gasoline purchased in the State.

The total receipts from the gasoline tax during the
period July 1 to October 31, 1924, were approximately
$286,400. Assuming uniform consumption of gasoline
per vehicle-mile and basing the calculation on the per-
centage of vehicle mileage as observed, the amount of
revenue derived through the gasoline tax from each
system would be $152,900 from the primary system,
$88,500 from the secondary system, and $45,500 from
the third-class system.

The total receipts from the gasoline tax for the cal-
endar year 1924 were approximately $522,000. Assum-
ing that the percentage of vehicle-miles on the three
highway systems remains throughout the year the same
as during the Been of the survey (July 1 to October
31), the annual gasoline-tax revenues derived from each
system are shown in Table 15, which also shows the
revenue per mile on each of the three systems, as well
as the revenue that could be collected from the same
traffic at tax rates of 2 and 3 cents per gallon.

TasLe 15.—Annual gasoline-tax revenues by highway systems,
based on 1924 revenues and traffic from July 1 to October 31,
1924

Tax of 1 cent Tax of 2 cents per | Tax of 3 cents per
per gallon gallon gallon
Highway system | Mile-

revenue | ZUG PEF) yevenue | BUC Per) revenue | 2Ue per
mnile mile mnile
All highways-__.-_| 23, 104 |$522, 000 | $22. 59 $1, 044, 000 | $45.19 |$1, 566,000 | $67.78
eMIMAry.soe.. 22 1, 630 | 279,000 | 171.17 558, 000 | 342. 33 837,000 | 513. 50
Secondary----__-_- 4,049 | 161, 000 39. 76 322, 000 79. 53 483, 000 119, 29
Hhind class=. 52 = _ — 17, 425 82, 000 4,71 164, 000 9, 41 246, 000 14, 12
| |

The forecast of traffic for 1930 indicates that traffic
will double during the period 1924 to 1930. Assuming
that the average annual mileage per vehicle in 1930
remains the same as in 1924 and that no radical changes
occur in the rate of gasoline consumption per vehicle-
mile during this period, a gasoline tax of 1 cent per
gallon in 1930 will produce $1,044,000, a tax of 2 cents
per gallon $2,088,000, and a tax of 3 cents per gallon
$3,132,000. .

Foreign vehicles using Maine highways also contrib-
ute toward the upkeep of Maine highways by payment
of the gasoline tax. In Table 11 the percentage of
utilization by foreign vehicles is shown to be 21.4 per
cent on the primary system, 9 per cent on the second-
ary system, and 5.7 per cent on the third-class system.

45029—25t——2

Assuming that the foreign traffic during the month
of June is equal to the foreign traffic during the aver-
age month of the period July 1 to October 31 and that
during the remainder of the year it is insignificant, the
gasoline tax receipts from foreign vehicles during 1924
were approximately: Primary system, $40,900; sec-
ondary system, $10,000; third-class system, $3,200.

The amount of the receipts which on the same basis
would be derived in a year from foreign vehicles on
the three highway systems at tax rates of 1, 2, and 3
cents per gallon of gasoline are shown in Table 16.

TABLE 16.—Annual gasoline-tax receipts from foreign vehicles by
highway systems, based on 1924 traffic

Tax of 1 cent per | Tax of 2 cents per | Tax of 3 cents per
gallon gallon gallon

Highway system siee- ee

| |
Total |Revenue| Total | Revenue} Total Feareae
revenue | per mile | revenue | per mile | revenue | per mile
|

$40, 900 | $81,800 | $50. 18
a

Primary ae eee $25. 09 | $122,700 | $75. 28
Secondary assess ee =e 10, 000 2. 47 20, 000 | 4.94 | 30,000 | 7.41
18 .387 | 9,600 | 55

Third class.-___.___- | 3,200 | 6, 400 |
| i

IMPROVEMENT OF OLR AE eet JUSTIFIED BY TRAFFIC

Whether or not the State is economically justified
in improving its roads and the degree of improve-
ment warranted—these questions depend to a con-
siderable extent upon the amount of the savings
in the operating costs of vehicles made possible
by the improvement. Assuming that the operating
cost is reduced 2.7 cents per passenger-car-mile
by constructing a concrete road where formerly
there has been an earth road,> and applying this
difference in operating costs to the average daily
traffic on the heavy-traffic routes of the Maine primary
system, the change in the type of construction is
shown to be fully justified.

For example, the average density of passenger-car
traffic on section 1 of the primary system, involving
300 miles of the most heavily traveled roads in the
State, was 2,042 cars. The total number of passenger-
car-miles per mile during the period from July 1 to
October 31 was, then, approximately 251,000. As
gasoline-tax receipts during this period were approxi-
mately 55 per cent of the total receipts for the year, it
is reasonable to assume that the traffic during this
period was approximately 55 per cent of the annual
traffic. On this basis, the total passenger-car mileage
per mile of the heavy-traffic routes of the primary
system for the year 1924 would be approximately
456,000 passenger-car-miles; and the saving of 2.7 cents
per passenger-car-mile effected by changing the type of
the road from earth to concrete would be approxi-
mately $12,300 per mile. As the average cost of
Federal-aid concrete roads completed in Maine up to
July 30, 1924, was $45,200 per mile, it will be seen that
the entire cost of building the concrete road could be
retired by the saving in operating costs of $12,300 per
mile in a few'years. With interest at 4 per cent the
time required would be slightly over four years.

5 The difference in operating cost of 2.7 cents per passenger-car-mile is based on
the researches conducted by the Iowa engineering experiment station under the
direction of T. R. Agg, results of which are published in Bulletin 69, Iowa State
College of Agriculture and Mechanic Arts, by T. R. Agg and H. S. Carter. The
costs are tentative and are applicable directly only to the surfaces and the vehicles
used in the tests. They may not express the true relation of operating costs on con-
crete and earth roads in Maine, but they are the most reliable estimates available
and seem reasonable,

It is believed that the 2.7 cents saving assumed
above is a conservative estimate of the difference in
operating costs on concrete and earth roads in Maine.
But it will be noted that in the example cited the con-
siderable operating savings of motor trucks, of which
there were 155 a day on the heavy-traffic routes of the
primary system, have been purposely ignored, as also
have been savings resulting from the reduction in the
cost of road maintenance. Indeed, it is highly probable
that it would be impossible to maintain an earth road
in satisfactory condition under the daily traffic on these

100,000

oS Se

1,000

afl _-t+——--

3
3
S319IH3A 40 YIGWAN

NUMBER OF VEHICLES

—— — PASSENGER CAR REGISTRATION
——— PASSENGER CAR TRAFFIC
—-— TRUCK REGISTRATION

--— TRUCK TRAFFIC

100 OO

1922

1919 1920 192)

YEARS

10
1916 1917 1918 1923 1924

Fic. 5.—Maine highway traffic and motor vehicle registration, when plotted to a
logarithmic scale, shows by the approximately equal slopes of the curves that the
rates of increase of traffic and registration are nearly equal

roads which is in excess of 2,000 vehicles a day. Ex-
perience of the Maine Highway Commission with re-
gard to maintenance costs on the more heavily traveled
highways of the State indicates “that traffic is being
carried on the bituminous macadam roads at a cost
one-sixth as much per vehicle-mile as is the cost of
carrying traffic on the gravel-surfaced highways.’ ®

Maintenance costs per vehicle-mile on a concrete
highway probably would not be higher than on a
bituminous macadam highway. Combining this sav-
ing in maintenance costs with the saving in vehicle
operating costs, the economy of the higher-type surfaces
on the more heavily traveled highways of the State
becomes even more apparent.

FORECASTING OF TRAFFIC MADE POSSIBLE BY SURVEY

One of the most valuable results of a highway trans-
portation survey is the development of fundamental
trafic information as a basis for estimating, with
reasonable accuracy, future highway traffic. A high-
way traffic forecast makes possible, for the period of
the forecast at least, the develo of a compre-
hensive highway program including the designation of
routes to be improved, the order of their improvement,
and the types of improvement required. The selection
of the improvement type should be based not only
upon a forecast of vehicle density but also upon the
weight of traffic units obtained by a motor-truck
capacity and gross weight analysis. The forecast
stabilizes the highway program. Uncertainty as to
the growth of traffic is largely eliminated and ue high-
way department is able to project a definite plan of
improvement over a Soria of years based on the
growth of traffic. By establishing a definite plan of
improvement highway development is carried on in a
more efficient and economical manner, and addition

§ Eleventh Annual Report of the Maine State Highway Commission, p. 17.

economy is effected by the elimiration of excessive
maintenance costs on unsatisfactory types of highway
surfaces.

It is possible by means of a forecast of traffic and
registration to establish the highway budget for a
reasonable period of years. Revenues to be derived
from motor-vehicle license fees, gasoline taxation, and
other sources of revenue can be predicted with reason-
able accuracy. If such revenues, together with other
available highway funds, are not sufficient to carry out
the necessary program, the amount of bond issues (if
the use of credit is justified in carrying out the program
of improvement) can be determined. By estimating
some time in advance the amount of bonds to be mar-
keted in any one year (when the bond-issue method of
raising revenue is necessary) 1t is possible to take
advantage of the most economical market for the sale
of these bonds.

GROWTH OF MAINE TRAFFIC, 1916 TO 1924

Fortunately, traffic figures are available in Maine for
one week each year from 1916 to 1923, inclusive.
During these years vehicles were counted from 7 a. m.
to 7 p. m. for an entire week, either in the latter part of
August or the beginning of September. Although the
total number of stations in 1923 was 58, only 26 of these
stations can be used for the whole period (1916-1923),
and even in the case of these 26 stations it is necessary
to interpolate some figures for the years 1916 and 1917.
Beginning with 1918, however, traffic records are
available for all of the 26 stations. The stations are
widely distributed over the highway system, and the
traffic density recorded each year is representative of
the change in traffic on Maine highways from 1916 to
1923.

The average daily number of trucks and passenger
cars has been computed from the week’s record at each
of the 26 stations, and these daily station averages
have been combined to yield average figures repre-

INDEX NUMBERS

1922

° +
“ a
a o

YEARS

Fic. 6.—Over the period 1916 to 1924, motor- truck traffic on Maine highways in-
creased at a slower rate than motor-truck registration; passenger-car traffic during
the same period increased at a faster rate than passenger-car registration

sentative of the traffic at the 26 stations in Table 17.
These figures give a reliable indication of the growth of
traffic over a period of years on the principal Maine
highways.

Comparing with these figures the data shown in
Table 18 representative of the registration of trucks
and passenger cars in the State during the same period
and plotting the data from the two tables to a logarith-
mic scale reveals the fact that the rates of increase of

)5)

TaBLE 17.—Average daily traffic at 26 stations in Maine, 1916 to

1924
aeP) | ——_.--
: Passen- |
Year | Trucks ger cars | Total

1 Figures for 1924 estimated on the basis of those stations in the 1924 traffic census
which were comparable with the above 26 stations.

traffic and registration are nearly equal, as shown

by the approximately equal slopes of the registration:

and traffic curves in Figure 5. The same fact is brought
out by Figures 6 and 7, in which the registration and
traffic over the period are compared on the basis of
index numbers derived by comparing the tabulated
registration and traffic figures for each year, in one case,
with the figures for 1920, and, in the other, with the
average figures for the period, as a base. These charts
should not be interpreted as meaning that the traffic
and registration are equal throughout the series of
years. They mean merely that the rates of increase
of the two differ only slightly and that traffic and regis-
tration are in nearly constant ratio from year to year.

Since this is so, a forecast of registration will also
predict future traffic, provided there is no important
change in the average annual use per vehicle. As any
change of this kind must, from the nature of the case,
be gradual; such a change will not greatly affect the
relation between traffic and registration during the
next few years.

TaBLE 18.—Registration of motor vehicles in Maine, 1916 to 1924

| |
Year Trucks | ape Total
UN eject ay a Se 1,991 | 28,991 30, 972
Gt een eee oan Spot oto escent enetoeen = 3,382 | 38,117 41,499
MSI) a a ee ee er 4, 200 42,372 46, 572
TNO) se Qo os Se a ee re 5, 795 47, 630 53, 425
2 ee See ee nee 8 one on wa casase cScehesn eee ce 7,512 55, 395 62, 907
DAWA See SSS eee 9, 936 67, 591 77, 527
Es Ee eee 13,842 | 78,697 92, 5389
hid Cente eens oon a. ee Os sare~cnen~sasasces 15,614 | 92,995 108, 609
i seen eee eee. eke cob a cco esesa-ascseose> 18,779 | 107, 933 126, 712

Table 19 presents the data shown in Tables 17 and
18, as indices of the average year. The graphic
presentation of these indices in Figure 7 shows clearly
the close agreement in the rates of increase of traflic
and registration.

TaBLE 19.—Relative growth of highway traffic and motor-vehicle
registration (average of years 1916 to 1923 =100)

sates
Year ‘Traffic le tions 2
|
44.2 | 48.3
54.3 | 64.8
56.5 | 69.6
87.5 83.5
99.3 | 98.3
122.9 121.1
150.5 144.6
184.8 169.7
199.5 198.0

FORECAST OF REGISTRATION AND TRAFFIC, 1924 TO 1930

This relation between the rates of increase of traffic
and registration may be employed to predict traffic a
reasonable number of years in advance by projection
of the increase in vehicle registration. Future regis-
tration depends upon future population and car owner-
ship per unit of population, and both of these factors
can be projected on the basis of their trends over past
years.

INDEX NUMBERS
SH38WNN X3O0NI

TRAFFIC 0
| — — — REGISTRATION
- 60

T T | 50

40 dF
x0 a x0
1916 1917 1918 1919 1920 192) 1922 1923 1924
YEARS

Fig. 7.—The parallel increase in the index numbers of traffic and registration indi-
cates that, considering all vehicles, the rates of increase of traffic and registration
in Maine from 1916 to 1924 were nearly equal

The registration of passenger cars and trucks per unit
of population in Maine from 1916 to 1924, inclusive,
is plotted as a solid line in Figures 8 and 9, respectively,
and trend curves projected to 1930 from these actual
figures by the method of least squares are shown by
the dotted lines. The results of these projections and
a comparison of the computed trend with the actual
figures for the period 1916 to 1924 are shown in Table
20.

TaBLE 20.—Persons per motor vehicle, 1916 to 1930

Persons per pas- Persons per
senger car truck
Year Faia aes a es
Esti- | Esti-
Actual | matea | Actual | timated
NO 6 Se cee teeee oe odes on See one eae 26. 2 24. 4 381 317
aR hy pale Sey eee ea eR eee ee eS 20. 2 21.7 225 257
1 OUS tee eee Some ne ana aS em 18.0 18. 2 182 | 187
LOLS Stee eee te ee Pee a one sae 16.1 15. 4 1382 | 137
1020 See ae Ee ee a ae 13.9 13.1 102 102
ODN SS os Se eee oo a cea 11.4 | 11.3 77.7 | 78.1
QOD Be te tiaweewe seat see ta sas 9. 84 9, 81 56. 0 60. 8
ip ia ee See ee Nee eae k See iS ee 8. 36 8. 62 49.8 | 48. 1
BA 7 pa i Nai Se ey EE Ee SE ELS By ES een 7. 22 | 7. 64 41.5 | 38.6
TOZ0 22 Se ee ose anda ns oes an a aee cas en an nn le ee 6.82 pine sees a! 31.4
NO 2G ee ee a es ee a oierae ea eam eee 612i oese oe | 25.8
HKG. 7 fab A Soe Bee, Beek ER a) eh aes Ae eS ees eae © 6508 Recut sas 21.4
O28 eee eae ee eee en ees ca ae 6302) eee aee 17. 97
1990 ee ee er er een eae ace 4557) |pecteawee | 15. 18
1}! lee ee UES Be Bo ee ea eee 4.19), \eeceeeanse | 12. 92

Applying the factors of estimated persons per pas-
senger car and per truck (Table 20) to the expected
population, the estimated registration is obtained as
shown in Table 21.

The experienced and expected rates of increase in
registration are shown in Table 22. The percentage
increase for each of the years 1917 to 1924, inclusive,
is computed from actual registrations shown in Table
18, and the percentage increase for each of the years
1925 to 1930, inclusive, is computed from predicted
registration as shown in Table 21.

TaBLE 21.—Estimated motor-vehicle registration, 1925 to 1930

Passenger-car regis- | Motor-truck regis- . .
tation Gration Total registration
=e Popula- meee bs " pula Aes
Year tion : : ,
| ncrease ncrease | Increase
| Number over 1924 Number over 1924 Number over 1924
Per cent Per cent Per cent
E87 a eee | 779, 902 1 107, 9383 0.0 | 118,779 0.0 | 1 126, 712 0.0
192682 oes | 782,544 | 114, 740 | 6.3 24, 920 32. 6 139, 660 10.1
1026 ane ee 785, 186 128, 300 19.0 30, 480 62. 2 158, 730 25. 2
NPY fee Se es 787,828 | 142,460 32.0 36, 810 96.0 | 179, 270 41.5
19282. Paces | 790,470 | 157, 460 | 46.0 43, 990 134, 2 201, 450 59. 0
1920 eee | 798,112 | 178, 550 61.0 52, 250 178.1 | 225, 800 78.0
193802222225 795, 754 189, 920 76. 0 61, 590 228.0 | 251, 510 98. 5

1 Actual 1924 registration.
From Table 21 it is apparent that motor-truck
registration may be expected to increase at a faster
rate than passenger-car registration. Figure 6 shows

that motor truck traffic increases at a slower rate
than truck registration and passenger-car traffic in-

LEGEND

es PERSONS PER PASSENGER CAR
ee ee ee ESTIMATED PERSONS PER PAS

NUMBER OF PERSONS PER PASSENGER CAR

a
2
i
ce
Ne
aw
GAIN
alte
Nel
i
a
ne
Eis
ali
les

Fia. 8.—Persons per passenger car, 1916 to 1980

NUMBER OF PERSONS PER TRUCK

364

35!

338

325

312

299

286

273

—_ |

260

247

aioeee

234

22)

208

195

182

169

156

143

oa] See] es Be SL
es on a
a | a es

eae Sasa

Bed

YEARS
Fic. 9—Persons per motor truck, 1916 to 1930

TABLE 22.—Annual increase in total motor-vehicle registration,

1917 to 1930

Increase | Increase
over pre- over pre-
Year ceding Year ceding
year year
Per cent Per cent
LOL, 2 eercdecnn ee ceeoenetasen 84.0% | 1026 seecae sateen. seceemaanees 13.7
1918. occas ade staeweaesasoane DEVE NB 52 eo oceor eae 12.9
1919.4 foc ane ssl asus ee eee es 14017 WN O28 See eae ee openers 12.4
1920 3-35 eee ee ee L767 WW! 1920 Soc eee eee coca eee 12.1
1021 S22 so ican ec otuntaaessese 93.211 1930 5 See ee 11.4
1900 ee eee eee eens 19.4 || Average annual increase 1917-
1993 S4c3 cok eee kn ace aeoeoeece 17.4 | 2A on wae ec ntoeene eens 19. 4
1994 Fe cch caste ee ee ce ease 16.7 || Average annual increase 1925-
1025 82 Seo Scsee ee eo hee eee 10.2 | 902 3 eae eee esceee 1201

creases a little more rapidly than passenger-car regis-
tration; but for total vehicles the rates of increase of

traffic and registration have been nearly equal. The
expected increase in total registration from 1924 to
1930 is 98.5 per cent, and, as shown by Figure 7, this
rate of increase may be expected for the total traffic.
Truck traffic will probably increase faster than pas-
senger-car traffic but not in the ratio of the increase
in registration as given in Table 21, because truck
traffic on the Maine highway system has not increased
as rapidly as truck registration in the State.

The expected increase in traffic of 98.5 per cent
from 1924 to 1930 is applied to the 1924 traffic at all
traffic stations of the 1924 survey. It is not expected
that traffic at every station will increase at exactly
this rate. Road improvements will modify the rate
at certain stations. The opening of new routes or the
development of new industries will affect the rate of
increase; a new shore resort or a new route to an old
resort would have considerable effect. Despite these
known facts, however, a study of the traffic counts
from 1916 to 1923 clearly indicates that the rate of
increase at a majority of the stations varied but little
from the rate of increase at all stations combined.

The expected traffic in 1930 at stations used in the
1924 traffic survey is given in Table 23. The figures
are for trucks and passenger cars combined. It is
anticipated that truck registration will increase at a
faster rate than passenger-car registration, and the
ratio of trucks to total vehicles on the road in 1930
will probably be a little greater than in 1924.

TaBLE 23.—Antictpated total traffic density in 1930 at all stations
of the 1924 survey

| Total Total |) Total
ae autlc ancl,
: pate : pate : pate
Station tranie Station traffic Station trafic
density, | density, | density,
1930 | 1930 |) 1930
| |
|
SG/Gi C3 a eeee Bae OSS PLZOE see eesoeeese 1, 099
Gy LOSe 645-20. aaeaasSan Zoi 126A toe Seeosce 363
LOS RGOL seat oe nese ASSO it 26 13.3 seme cee 2, 014
TOG | OOzesassene sees SOGR, L2iaeessae es i lei
SNG44 al G7 ee ADAH 198 ues eee eet 286
a a ee eee 1, 497M 120i ers Ne ek 504
PACD LP || S(t ieee eee ee T038:||| 1302-6 Se-n-~ = 1, 145
LOOM Piste seet ences Tall oles eee a 472
BBG || Phere en ta hotel hy ae ae ena S. 1, 552
TOGA W2es0. Ssceseces a (O20 Soneeeetas oe ene 1, 796
2s OUGa I oseee enone ee La Oy all otaee 2 seekers 1, 097
DOLE I acoenme cee ae ok 2, OSAGNL LoOneeewse ee naae 617
Pook Wl) fOssssoesee so= 2 BOOM WSO Losec Sessa se 1, 604
2 SOOM Ok are wen cot es aos L528 4022226 soe 2 1, 840
BID 09-7) len ele See a 3,005) |||$403 2552 ae sae 3, 384
S27 irl) Odeaseaaseat sane 2, DOOGI| 40425 Se eee See 5, 815
4.293) |\) 04-522 oe sono es Bb 2ban | PA00s- bese ee 3, 356
D2 240 Ob ssa ee ot SUS Se OGBY) G4 062.. See ee 11, 509
SH O0Si || 0Gsee=22 see oe SOUS 2407ss es Stes. 2 7, 661
(a) dal] het eee eee TOU WeOS ice we nares 2, 963
Glas PS whee sce BE2ANG ec ees | 6,242
TO7OUI OO pees ees se oda Al Oo sessed 3, 247
26028) LOO ee a seen n= LOD Wa2leoeos aes eee | 2,177
2. 20S aie OL ease 2a 7 80n| A22 eee ee eee sl 1, 248
2200 I, 102i 25 - soso L369 U||P423 ee eons see | 1, 733
14497) 103 Se Sees ee Se L226: ||, 424: .2S28 oe ae | 3, 918
Tit ea Ne ee 2 OC0U ALL aces sean eee! 689
O35 |#1LObeeees acess: $30) i) 426 se 8- 28 oo- =. 2, 197
(i) MU ee a 50654272 cas sees | 2, 757
Dol) Welles sone eee ee 917 Ds, ee a eee 1, 572
T8020 d2oseaenes ee | ae. Ba eee | 3, 283
HI OOO) lod een we 206 5||' 490 see eee 4, 009
1,473 |

1 Before change in location; change occurred as follows: Station 1, Sept. 28, 1924;
station 126, Aug. 28, 1924.
2 After change in location.

TRAFFIC EXPECTED TO DOUBLE BETWEEN 1924 AND 1930

Summarizing the facts brought out in the foregoing
discussion, it is found that Maine registration doubled
in the four years from 1916 to 1920. It doubled again

in the four years from 1920 to 1924, and the forecast
anticipates that it will double again during the six
years from 1924 to 1930, as shown in the following
tabulation:

Maine motor-vehicle registration

Year Total registration
LOT GB ee See ee wi ee Boe ied 0 aS tree 30, 972
LOCU eee Bkae we Cee be ees ot ee ee le 62, 907
MM 2 Sie eee Nanas ell #74) PAOD GS ew aa Oe ew sh See 126, 712
193 (ee ee ae ed Oe ee ON ee ee eS 1251, 510

1 Estimated.

In almost exact coincidence Maine highway traffic
doubled in the three years from 1916 to 1919; it
doubled again during the four years from 1919 to 1923
(this is the more significant period, since the traffic
figures for 1916 and 1917 are less reliable); and the
forecast anticipates that it will double again during the
six years from 1924 to 1930, as shown in the following
tabulation:

Total daily traffic at 26 stations

Year. Total daily traffic
191 Gls oo eae Be RR iee tes eae 7, 316
LOL OS ee ae Senn ee SOs MOON ae 2 ea. te ee ae 14, 468
LO 2 ae eee eee Pee Diese eens eee See AS RL ee 30, 569
aR She} OP epee 5 Seatins ew Be RL yin ed Pare A bee eee) Dig 1 60, 527

1 Estimated.

The Eleventh Annual Report of the Maine State
Highway Commission gives a tabulation of the results
of past traffic surveys, which differs somewhat in respect
to the rate of increase from the figures presented above.
The commission’s figures are given in the first three
columns of Table 24, in the fourth column of which are
given, for’ comparative purposes, the indices of total
traffic at the 26 stations included in the analysis re-
ported herein. It will be noted that the number of
stations averaged in the commission’s analysis differed
from year to year, while the analyses made in this report
are based on the same 26 stations each year from 1916
to 1923, inclusive.

TaBLE 24.—Comparison of indices of traffic taken from report of
Maine Highway Commission and this report
| |
| | Index of
Average total
| Number} number | Index | traflic
Year | ) of vehi- | (1920= at 26
| stations | cles per 100)! | stations
day | (1920=
| _ *400) 2
| |
we 2 xe e = =| aa 2
IRON nee SO Seen AE ps re ge oi ee) oe a ally oa 2 A 45
LOLS Se a ee SE eee a 18 428 | 83 | 55
LOLS Ss Steen: Sarin Sea aoe ees ase eps Oe 8 19 483 94 | 57
101 Geel SE a ae 4 38 504 98 88
LODO A sie eel et ee ee 41 515 100 | 100
Ope a ae ee See, ee re ee | 43 715 139 | 123
1022 a eee te ee ke en an ees 46 767 149 | 152
1025 Bee oe eee Re ee ad 49 961 187 | 186

1 Eleventh Annual Report, Maine State Highway Commission.
2 Based on 26 stations, 1916-1923.

The commission’s report states: ‘It is seen from the
above figures that traffic in 1923 was two and one-
fourth times as heavy on an average as in 1917. It
should be borne in mind that new stations added from
year to year were not located on the heaviest traveled
highways. Several of these stations were off the
State highway system, the object of the commission
being to secure traffic data which might indicate the

location of roads which eventually should be added
to the State highway system.”

Despite the difference in number of stations there is a
close agreement between the indices of total traffic
at the 26 stations and the indices at from 41 to 49
stations from 1920 to 1923. The number of stations
from 1920 to 1923 is more nearly constant in the com-
mission’s report. But the indices of traffic based on
data from a number of stations varying from 18 in

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, & ie PRIMARY ROAD - SOLID BLACK ow
SECONDARY ROAD - OPEN SPACE

Fia. 10.—Anticipated density of traffic on primary and secondary highway systems
of Maine, July to November, 1930

1917 to 49 in 1923 are misleading for prediction pur-
poses. ‘The adding or dropping of stations from year
to year makes the average number of vehicles per day
(per station) incom parable in the given years. The
ane report recognizes this defect in the note quoted
above. .

The traffic forecast herein set forth is tentative. In
all fairness it must be recalled that the Maine traffic
records for the period 1916 to 1928 are for only one week
per year, although that week is in the same part of
each year. A second consideration, which is not so
important in its effect upon the conclusions, is that
data for 1916 and 1917 are missing at some of the sta-
tions, and therefore it has been necessary to inter-
polate some values for these years.

The location of the 26 stations used to measure the
increase of traffic in Maine, 1916-1923, is a basis for
confidence in the application of the increases there
recorded to the 1924 traffic data, since the 26 stations

are widely distributed throughout the State on the
routes covered by the 1924 survey. Neglecting such
factors as the effect of major mechanical improvements
to automobiles, it is believed that the traffic estimates
here given will closely represent traffic on Maine
highways in 1930.

A definite betterment of the method of planning
future highway improvements is represented by
Figure 10, which shows a forecast of the average daily
traffic on the principal primary and secondary routes
during the period July to November, 1930. The
problem of caves ing such a forecast in Maine ‘was
simplified by the fact that the Maine Highway Com-
mission kept a record of traffic each year at a selected
number of key stations from 1916 to 1924. As a
number of State highway departments have had the
foresight to preserve similar traffic records on their
primary systems over a period of years, it should be
possible to make similar forecasts of future traffic in
these other States.

SUGGESTED PROGRAM OF HIGHWAY IMPROVEMENT

The forecast of expected registration and traffic is of
particular importance at the present stage of highway
development in Maine. The State has reached the
second critical stage in its highway improvement pro-
gram. ‘The first stage may be called the gravel-road
stage. During this first period traffic demanded high-
way service over a large mileage, and the highway com-
mission wisely inaugurated the policy of stage construc-
tion based on the theory of providing highway service
over a large mileage rae than a concentration of ex-
penditures on a limited mileage. The gravel road met
this demand. ‘Traffic, however, was relatively light
and, with the exception of a comparatively small mile-
age of heavy-traffic routes, gravel furnished a satisfac-
tory and economical surface. The proper policy was to
improve a large mileage of roads to the gravel stage and
confine improvements of a higher type to a compara-
tively small mileage of heavy-traffic routes. The
Maine Highway Commission has followed this policy in
an excellent manner.

The second stage of a highway improvement program
may properly be called the reconstruction and high-type
improvement stage. When a State reaches this stage
it is essential to set up a definite improvement policy
for a period of years. Maine experience indicates that
a gravel road will not carry over 500 vehicles per 12-
hour day successfully unless it is surface treated.’ The
average daily density of traffic on the entire primary
system for the period July 1 to October 31, 1924,
was over 1,000 vehicles.

Clearly, Maine is now entering the reconstruction
and high-type improvement stage. The questionable
economy of attempting to maintain a gravel surface on
heavy-traffic routes is demonstrated by the mainte-
nance costs on sections of heavy-traflic gravel roads in
the State.®

The 1923 maintenance costs per mile per vehicle on
the Waterville-Bangor highway are more than double
such costs during 1919 and 1920. Traffic has practi-
cally doubled during the same period. Similar mainte-
nance costs per mile per vehicle for 1923 on the Wool-
wich—Bangor highway are double the costs for the years
1918 and 1919. ‘Tables in the same report ® indicate

(Continued on page 67)

7 Eleventh Annual Report, Maine State Highway Commission, p. 17
8 Ibid., p. 15.
9 Tbid., pp. 16-17

THE WAGON AND THE ELEVATING GRADER

AN ECONOMIC STUDY OF THE WAGON—ELEVATING GRADER COMBINATION IN THREE PARTS

BY THE DIVISION OF CONTROL U. S. BUREAU OF PUBLIC ROADS
Reported by J. L. Harrison, Highway Engineer

PART II.—THE INFLUENCE OF DESIGN ON ELEVATING GRADER COSTS

grader-wagon outfits and the conditions which

must obtain if a high rate of production is to be
secured were discussed in Part I of this article. The
proper adjustment of the size of the wagon train to the
special conditions of the project in order, (1) that the
number of wagons shall be sufficient to move the output
of the grader as rapidly as it is produced, and (2) that
their number shall not exceed the supply that can be
utilized without periods of idleness by the grader,
was shown to be dependent not only upon the output
of the grader but Any upon the distance the excava-
tion must be moved and the rate of wagon travel.
The length of haul is an especially important factor in
elevating grader work, and it is peculiarly affected by
the design of the road.

In all grading operations rational bidding must take
account of the haul as a controlling factor. This is a
comparatively simple matter when the material is
moved with the simpler forms of equipment, such as
the wheeler and the fresno. When these implements
are used cuts can generally be taken out substantially
as indicated by the balance points shown on ordinary
highway plans, and the actual haul will therefore be
found to be closely in agreement with the calculated
haul, so that a knowledge of the average calculated
haul generally suffices as a general basis for estimating.

But such data are inadequate for careful bidding on
elevating grader work. In the first place the transfer of
the loading function to an independent apparatus intro-
duces an expensive operation which, whether the haul be

ee factors influencing the production of elevating

which is an inseparable feature of the work, does have
a most important bearing on the cost because of its ef-
fect on the relation of the moving to the loading element,
i. e., the wagons supply to the grader. It is customary
for the contractor to supply a fixed number of wagons
with the elevating grader. The supply furnished may
be in proper relation to the grader output for the aver-

OF WHOLE CUT
ENGINEER'S
BALANCE LINE
OF WHOLE CUT

ENGINEER'S
BALANCE LINE

ENGINEER'S
BALANCE LINE /

CENTER OF
CENTER OF

A~- AVERAGE HAUL AS GUSTOMARILY SHOWN BY DESIGN; APPROPRIATE FOR FRESNO WORK.
B- ACTUAL AVERAGE HAUL WITH ELEVATING GRADER.

Fic. 1.—Diagram illustrating difference in average haul on fresno and elevating-
grader jobs
age haul; but from cut to cut, and even in the same
cut, the haul will often vary between limits which, if
the haul is short, leave the teams idle much of the time,
and if the haul is long, leave the grader idle much of the
time. For this reason the average haul is not a proper
basis for estimating where elevating graders are to be used.

PECULIARITIES OF HAUL ON ELEVATING GRADER JOBS

Moreover, the average haul on elevating grader work
differs from the average haul as calculated for fresno

long or short, accounts
for a largerpart of the
total cost than the corre-
sponding operation on
wheeler and fresno jobs.
In the second place the
movement of the ma-
terial in the large
volumes made possible
by the wagons reduces
the cost of movement, so
that it becomes pro-
portionately less im-
portant than on wheeler
and fresno jobs. By
reason of both of these
differences the length of
haul on elevating grader
jobs is less important in
its bearing on costs than
on the wheeler or the
fresno job, and _ the
average haul is relative-
ly less significant.

But, though thelength
of haul is less significant
than with other methods
of operation, the fluctu-
ation in haul distance,

HE generally accepted idea of the usefulness of design

is that of an instrument for letting contracts and a

guide to be followed in construction. That with a
given limiting gradient and rate of curvature, and without
change in the quantity of earth moved, the cost of grading
with an elevating grader outfit may be varied by as much as
20 per cent, and yet the road produced in each case will be
practically the same is a fact quite generally lost sight of.

Again, variation in design may bankrupt a contractor
or give him a profit, although, in each case, his contract
unit price may be the same and the completed road
equally useful and economical in the service of highway
transport.

Fluctuations in the length of haul are primarily respon-
sible for high unit costs on elevating-grader projects.
Within the well established limits of wagon haul it matters
not so much whether the haul be relatively long or rela-
tively short; but when the contractor is put to the neces-
sity of moving a considerable part of the material a long
distance and another considerable part a short distance,
unit costs for one part or the other are likely to be exces-
sive. The reason is that the adjustment of the size of
wagon train to the output of the grader which is appro-
priate for the long haul can not be appropriate for the short
haul, yet practical considerations make difficult the changes
in the size of train, which are economically necessary.

In this article the effect of length of haul is treated in
detail and illustrations are presented to demonstrate the
important bearing of design, involving hauls of various
character, on the cost of elevating grader work.

or wheel-scraper work.
With the latter form
of equipment the length
of haul grows as the cut
and fill are extended,
and the actual haul
generally agrees closely
with the haul distance
as shown on the plans.
But the elevating grader
does not open cuts jas
they are opened by
wheelers or fresnoes. It
opens the whole cut at
one time, moving back
and forth over such a
distance as the general
contour of the cut indi-
cates to be desirable but
always as long as possi-
ble up to the full length
of the cut. This gen-
erates an extension of
the haul distance, and
the actual haul becomes
the distance from the
center of mass of the cut
as a whole to the center
of mass of the fills to

60 ‘

BP. BP.3
0 274 852 889 1004123 422 0 0 106 175 I ) 0 0 0 CY)
0|0 68 477/92 S07 SIO 763 875 765 605 S08 428 310

BP.)
CuT 0 0
FILL+1S% B00 493 1060 166 0 0

pm bi T

QUANTITIES- CUBIC YARDS
100 261 «290 204 «163422

150 150 222 24 6 0

BP.4 BPS
437 2454 558316 180 0 o 28 «8646 )6«6©% 6313, S789 — 978 «B76

Q 0j7 3271272530 756 458 290 266 104 0 0 0

f SO DAYS-IOWAGON OUTFIT REQUIRED TO
AV. LENGTH | HOVE 4363 YOS. FROM CUT C INTO FILLS

A |

i : ,
PA <— at > een tema a a

VERTICAL — FILL 2 2

AV. LENGTH OF CUT=3404
CURVE300!
ie =r a

ice
eh
La | | Ree Lee
| CENTRE OF MASS OF CUT

THIS 1M GENERAL GOVERNS ACTUAL
a ——] | AVERAGE LENGTH OF HAUL

: OF CUT! —+ — sm Z
| | ee | : fey les '
see
aed pais Se
> END :

i. r tt m= ho's

, |
BASE LINE Ke
digg

1 iS
pF Av AV. HAUL WITH ELEVATING GRADER FOR YARDAGE IVOLVED Sj -

CUBIC YARDS

B*PLUS WAGON MANIPULATION |
C*AVERAGE WAGON TRAVEL FOR YARDAGE INVOLVED |

“ty M=AVERAGE HAUL AS CUSTOMARILY SHOWN

X-Y=AVERAGE HAUL LINE |

-—5™ 1033 YDS
TOTAL QUAMITY FRCH CUT'C: 4363 CU.YDS.

7 SCALE: MASS DIAGRAM-VERTICAL 1000 CU.YDS. TO THE DIVISION
FEET «= ”

AT THE CUT THE WAGON LOOP WILL VARY

eA, TOTAL TIME REQUIRED 5.0 DAYS
(c= 365'y | oe cee es \N LENGTH BETWEEN THESE LIMITS La
3 | HORIZONTAL 100 * eS
25 30 35 45 50 $5

40
STATIONS

Fig. 2.—Original design of sample grading project, illustrating effect of fluctuating haul distance

which material is delivered. The difference in the two
cases is illustrated in the diagram, Figure 1, and in
Figure 2 which is the reproduction of the center-line
profile of a part of an actual project.

Between balance points 1 and 3 in Figure 2 there is a
cut A, which is divided so that part of the material is
hauled to each of two fills. The mass diagram which
appears below the profile shows that the average haul to
fill 1,as commonly calculated, is about 360 feet and to fill
2 about 110 feet.1. But in taking out material with an
elevating grader cuts of this kind will not be divided as
they would be for wheeler or fresno work. The grader
will work back and forth over the whole length of the
cut and the material will be hauled either to fill 1 or to
fill 2, with the result that more or less material des-
ignated by the engineer as belonging to fill 1 will be
placed in fill 2 and vice versa. In a symmetrical
cut the result of this practice will be to lengthen
the average haul so that it becomes the distance
from the center of mass of the cut (line xy as shown
on the mass diagram) to the center of mass of the
fill. In this way the average haul to fill 1 israised from
360 to about 400 feet and the average haul to fill 2
from 110 to about 250 feet. A study of the other cuts
in Figure 2 shows the same tendency toward an increase
in haul distance in all except cut D, all of which is
hauled to one fill. Where this occurs no extra haul is
generated by the use of the grader.

The result of increasing the haul to the center of mass
of the cut as a whole in cut A is more marked in its
effect on the haul to fill 2 than to fill 1. This is gen-
erally the result where the quantity to be moved in one
direction is considerably larger than the quantity to be
moved in the other. The haul determined in this way,
however, may not be exact. Thus, if cut A had been so
nonsymmetrical that the depth of excavation between
stations 27 and 29 had considerably exceeded the depth
of excavation between stations 25 and 27, the grader
might be operated here on a short loop until the material
remaining to be taken out was reasonably symmetrical
over the whole cut. If this were done the material for
fill 2 would be secured with a somewhat shorter haul
than the method of calculation described above would
indicate.

Similarly, the manner in which even a symmetrical
cut is taken out may somewhat affect the length of
haul. Thus, if instead of taking a first cut along line
ab it is taken along line cd, the haul may be somewhat

1 There are a number of methods of calculating haul. The one here used, which is the
simplest and quite accurate enough for the purpose, assumes that the average haul is the
distance between the points halfway from the base to the peak of the mass curve on the
cut and fill slopes.

affected. But in operating elevating graders the
general practice is to make the runs as long as possible.
and for this reason if the cut is anything like aya
cal the tendency is to make the average haul the dis-
tance from the center of mass of the cut to the center
of mass of each of the fills or fractional parts of fills
into which the cuttings are placed. This should there-
fore be used as the basis from which to calculate haul.
But it should be recognized as an approximate rather
than an exact basis, as special conditions of the sort
mentioned will often enter to make the actual results
somewhat different from the theoretical. Lack of
symmetry in the cut is responsible for most of these
special considerations. It creates short grader runs,
unproductive runs, nonuniform bite, etc., none of
which need affect the haul distance as theoretically de-
rived, but all of which do, more or less, because, under
field conditions, there generally is less thought given
to these matters than isneeded tosecure accurate results.

EFFECT OF LAYER DUMPING AND WAGON MANIPULATION ON HAUL

Layer dumping also tends to affect haul. If it is
required, as it should be, there is a tendency to increase
haul at the fill. Thus, in Figure 2, it may be assumed
that instead of placing fill 2 as shown on the plans the
material secured from cut A is placed in two layers
which extend well beyond balance point 3. In such
a case the actual average haul instead of being 250
feet might easily reach 300 feet. There is no way of cal-
culating such extensions in advance. They are rather to
be considered as an element likely to create excess haul
and therefore one which a contractor should watch
and avoid. It is not at all necessary that layer
dumping cause any considerable amount of extra haul.

Besides these conditions which affect haul there is
another arising from the manipulation of the wagons
themselves. The general operation of the wagon
train, somewhat distorted for the purpose of illustra-
tion, is shown in Figure 3. As the elevating grader is
moved toward the dump the empty wagon must
return to a point some distance back of the loadin
wagon in order to reach position. Let it be assume
that wagon 10 is loading along ab and wagon 11 is the
replacement wagon. Let it also be assumed that the
average distance required for picking up a load is 75
feet. The distance that the load as a whole must be
hauled will, of course, be calculated from the center
of the distance over which the load is picked up.
There is then a necessary addition of 374 feet to the
average distance over which the wagon will be moved
which addition covers the distance traveled by the

QUANTITI

BP.6
954 483339728 335 202 150 W2 157 S26 1068 1252 896 283 46 0

0 QO

ES-CUBIC YARDS
B.P.7

oom BPS

BPS
NS $02 750 750 2200 489 315 % 178 130 100 O 0 0 0 0 0

W2 1090

eae eens 2-5 0 O- 0 “0 150 “805

1S72 657 \281 7I2

HE 2 0/0 0 0 64h 32% 353 303 337 564 635 762 770 888 236

ee —_ ee et |
Pee all le | AAV. LENGTH OF CUT» 150°
L—" 5 + + + + SS a a el Se SS
p— I i |g. VERTICAL CURVE:400'
J preter eal |
MAX.CUT NEARLY 700! c
AV. CUT ABOUT Sso’__|
THOD B f T END OF JLLUSTRATI
PROFILE +++ Attar — pur nor THE End oF | 4.900
x fate b+ / 18 = 80 THE PROJECT ——+}
A= 580° | esi b C=7
| , B= ah } = = = 43,000
2.000 | RNAL BALANCE at; |
251 CU.YDS. * ae 42000 ©
iat ia, : = :
i AS pena tl S20 ie. L - 1.000 2
= Lovaas ase une | _/| | 2
Z| METHOD B 8 pec METHOD A & 3 : Be Nee | : weT0s6 i
Foca ae ¢ +180 -—} —}—MASS-| — ins Ween engine cs a Ce r -|— DIAGRAM —— faut’ = Sango ss 11.000
2000. reall ail 4 ; Kies C* 440' y CASTED= 2256 » »
60 65 70 75 80 6s 30 2,000
STATIONS
Fic. 2.—(Continued)

wagon before the beginning of the average haul dis-
tance for the total load is reached. To this must be
added whatever distance was traveled after wagon 11
fell in behind wagon 10 in order to be in a position for
prompt replacement [ven if the wagon train is in
close harmony with the output of the grader, there
must still be a short distance allowed for this purpose,
say from 10 to 15 feet. If the haul is to fills on both
sides of the cut, this extra distance will generally be
avoided; but prevailing practice is against taking out
cuts in this way, because it doubles the force employed
on thedumps. With wagons moving toward the dump,
therefore, there is then an excess of wagon travel over
iS average haul, for the load as a whole, of about 50
eet.

A similar situation prevails when the grader is mov-
ing away from the dump. In this case each wagon must
move an average of 3714 feet beyond the average haul
for the load in order to secure its full load. Moreover,
in driving to a clearance for the replacement wagon the
loaded wagon must move ahead far enough to permit
the replacement wagon to reach the loading position
before a turn is made. This will require at least 15
feet and often more. Whether the grader is moving to
or from the dump, therefore, the wagons actually
travel about 50 feet further than the average haul for
the load, the additional travel bemg necessary in the
interest of manipulating the wagons at the grader.
Applied to the cut which has been used as an illustra-
tion, this results in an average wagon travel of 450 feet
to fill 1 and 300 feet to fill 2, with the possibility that
when layer dumping is required the haul to fills as
short as fill 2 will be somewhat further increased.

WORKING THE WHOLE CUT etn arts ADVISABLE DESPITE LONGER
AUL

Ordinarily the contractor will not find it to his
interest to avoid the extra wagon travel that arises from
the failure to follow the engineer’s balance points.
With normal efficiency in the operation of the grader
and an adequate wagon supply, a cut such as A, which
averages about 340 feet in length, permits of working
the grader about 50 per cent of the time, but if such a
cut were divided into two parts and taken out in
accordance with the engineer’s balance points the
shortened run would permit the grader to work only
about 34 per cent of the time in the shorter cut. The
resulting loss in output would generally outweigh any
advantage that might be obtained from the shortened
haul, since it is probable that the wagon time saved by

reducing the haul would be wasted in waiting for loads,
for it must be remembered that the wagon train gen-
erally consists of a fixed number of wagons; therefore,
unless ‘the grader output is correspondingly increased,
shortening the haul merely tends to cause a piling of
the wagons. This is invariably the result when the
haul is within the capacity of the wagon train. If the
haul is beyond the capacity of the tram, the reduction
in haul by splitting the cut may overbalance the reduc-
tion in grader output, but cases of this sort are com-
paratively rare, and to take advantage of them the
contractor must have at his disposal the accurate data
supplied by the mass diagram.

AVERAGE OUTPUT 1,000 CUBIC YARDS A DAY

An analysis of the average wagon travel when com-
bined with an analysis of the average length of each
cut, by which the possible output of the grader is indi-
cated, will serve to avoid many of the speculative risks
contractors encounter in elevating grader work. To
be really effective, however, the analysis should be
extended to include a study of the haul cut by cut, and

HAUL FOR WAGON 10
HAUL FOR WAGON I!

PATH OF LOADED WAGONS —
\\ a rmorrerumucmens |)

PATH OF LOADED WAGONS —
Vee ota ncde)

5)
Snes Mies Ses FOR WAGON 10 -

HAUL FOR WAGON I!

Fic. 3.—Operation of wagon train on each side of grader loop

the results of this analysis developed on the basis of
some standard unit of production. For this purpose,
in the description of ae method which follows, an
output of 1,000 cubic yards per day has been used.
he bureau’s studies of elevating grader projects
indicate that the average length of cut is about 450
feet. The studies also mdicate that, when the wagon
supply is adequate, ordinarily eflicient operation results
in an exchange of wagons in about 11 seconds. The
time required to load a wagon averages about 23
seconds. With due allowance for breakdowns, clean
outs, rests, etc., these conditions permit of securing

BP.
oO

BPI BP2
cuT 0 0 320 1/80 ISI9 41 1960 920 O

QUANTITIES~ CUBIC YARDS
3

BP4 BP.
240 250 16) 113 256 1045 142171 850 18 0 O

0) 1G0ee2O5a ca One OlnO Om Om SI 0. 0 43 70 258 430 410 310
FILL+15% 300493 1060 166 0 O[0 0 O 138 [21 184 490 69 753 727 182408 437 320 168 146 241 297 153 0 OJ0 70 4525S 756 458 319 310 84 0 0 0
i cu A |oox uate CuRVeZsg rT Ae
x re) CURVE= 5 . 0 1 H !
alle _ 2 Son !.9.% |CURVE'SO | 9.0% meee | + aVERAGE LENGTH OF CUT» 200FT-

~ VERTICAL
CURVE*S0

7 O
ERTICAL ed ey

CURVE: 150)
TAV. LENGTH OF CUT= 375'~

|
Sis

CUBIC YARDS

A= AVERAGE HAUL WITH ELEVATING GRADER FOR YARDAGE |

B= PLUS WAGON MANIPULATION +} [ t

= AVERAGE HAUL LINE |_| i aac

— C= 875'+—_+ MASS ~ + DIAGRAM i

pers

SCALE-

_| MASS DIAGRAM-VERTICAL 1000 CU.YARDS TO THE DIVISION i

+ | PROFILE “ LOMIMEEETION: (aienlia
HORIZONTAL |100 “

30 3s

Fia, 4,
the cuts.

an output somewhat over 100 cubic yards an hour
with only average efficiency in operation. Allowing,
then, for the losses in working time which, on practically
all jobs, result in reducing the working day to some-
thing under 10 hours, it is still possible for the average
contractor, with no change in managerial policies and
no improvement in general efficiency, to secure an
output of 1,000 yards a day if his ee supply is
adequate and his cuts are of standard length. ‘This
output has therefore been used as a basis from which
to work in showing how the length of cut and the
length of haul are likely to affect output and why
contractors often lose money on work of this character
through a failure properly to gauge the effect of those
elements.

CORRECT BIDDING IMPOSSIBLE WITHOUT STUDY OF HAUL

It will be seen, in cuts A and B, Figure 2, that a
knowledge of the average wagon travel does not
cover the situation. Thus cut A can be taken out with an
average wagon travel of 450 feet for the material moved
to fill1. The mass diagram shows that there are approxi-
mately 3,000 cubic yards of material to be awe into
this fill. But of this amount 1,000 cubic yards calls
for an average wagon haul of about 520 feet, 1,000
cubic yards an average haul of about 450 feet, and
1,000 cubic yards an average haul of 365 feet. In
comparison with this the mass diagram for cut B shows
about 5,000 cubic yards of material to be placed in
fill 3. Of this material 1,000 cubic yards must be
moved 1,470 feet, the second 1,000 cubic yards 1,290
feet, the third 1,000 cubic yards 1,180 feet, the fourth
1,040 feet, and the fifth 1,000 cubic yards 860 feet.
What is perhaps the most serious problem the con-
tractor has to meet in this sort of work is brought out
clearly by the study of these two cuts. An output of
1,000 cubic yards has been set up as the standard day’s
work, assuming normal efficiency. But if the eight
standard days’ work in these two cuts are sabeeal it
will be apparent that the work can not be performed
in eight days with any ordinarily constituted outfit, be-
cause the range in haul distance is too great. Such a
tabulation, in which the effect of length of cut has been
purposely omitted, is shown in Table 1.

Table 1 illustrates clearly the dependence of produc-
tion on the proper adjustment of the wagon train to the
length of haul and the danger of depending on the aver-
age wagon travel in analyzing elevating grader projects.

First re-design of sample grading project, illustrating the possibility of equalizing haul distances.
This assumption limits the reduction of haul to about half the distance center to center of cuts

40
STATIONS

45 so

In this design it is assumed that fills will be built entirely from

TaBLE 1—Effect of length of wagon haul on elevating grader
production and time required for grading

(Based on cuts A and B, Figure 2)

=
Num- | Using 8-wagon Time
| ber of outfit re-
| wagons}. 22 Spe | Ce Equiv-
Material moved ere Wagon quired able fe alent
foal terial | 22Ul | for full | Team | Grader pany each vate
output | time | time D 1,000 8
' of | wasted | wasted | cubic
| grader yards
“| je =
Cubic Per Per Cubic | Cubic
yards Feet cent cent yards | Days yards
| ee ees 1, 000 520 | 8 0.0 0.0 1, 000 | 1.0 1, 000
ce one 2 SS er 1, 000 450 | 7 1255) 0.0 | 1,000 1.0 1, 000
[at a 1, 000 365 | 6| 25.0 0.0 | 1,000 1.0} 1,000
Oo tee se sae) 000 1,470 | Hata es ee 50. 0 500 | 2.0 2, 000
BIS ENS cf ce me 1, 000 1, 290 | Lbs 47.0 530 | 1.9 1, 887
On) eee see 1, 000 1, 180 13 eee se oes 38. 0 620 | 1.6 1, 613
breed, Lame eee 8 1, 000 1, 040 1 2 ees eee 33. 0 670 1.5 1, 500
Ca eee | 1,000 860 10 se a oe ae 20. 0 800 1.2 1, 250

1 Based on standard daily production of 1,000 cubie yards.

Time required for movement of 8,000 cubic yards, 11.2 days; probable average out-
put per day with 8-wagon outfit, 720 cubic yards.

Cuts A and B are on one project and only a short dis-
tance apart. The average wagon travel from cut A to
fill 1 is 450 feet, and from cut B to fill 3 it is 1,180 feet.
These averages would indicate that trains of 7 and 138
wagons, respectively, would be required for 100 per
cent production at the grader as against the range of
from 6 to 16 wagons shown by the detailed analysis
actually to be required if full production is to be se-

cured. If an 8-wagon outfit were used, 100 per cent
orader ee could be obtained in cut A, but the
longer hauls of cut B would reduce the average daily

output for both cuts by 28 per cent. Even if the long
wagon train indicated by the average travel to fill 3
were provided, full production at the grader still could
not be Senna at all times. The point to be
stressed here is that haul varies over such a wide range
that no contractor is in a position to make other than
a random guess as to what the work on any project will
cost without a careful analysis of this element.

THE MASS DIAGRAM AS A MEANS OF CONTROLLING FIELD

OPERATIONS
The analysis of elevating grader work through study
of the mass diagram can be made an effective means
of controlling field operations. Thus, cut E is a sym-
metrical cut from which approximately 6,000 cubic
yards of material are secured. Wagon haul per 1,000

QUANTITIES ~CUBIC YARDS
BP.8

0 00 0
150 805 1112 N00 18541 930 712 366 25

B.P.6 BP7
31039 96234 320 187_— (120,95 660155 535 1120 1320 896 283 46 O

Meaty oe 45 224 303 263 510 0 0O 0 0
AVERAGE LENGTH OF CUT=350°
ail |

STATIONS

BPS BP
7 WS S02 1470 34017801347 270 «25763 0
0 O0jJ0 0

Wal They Wx Las eer wea

CASTED* 2462

| |
— ze | oc | ee a
' 1 i]
a ah hea LENGTH OF CUT®* 300 FT. }—_;—_+— +
| | | | |
| |
142.00° ie OVERTICAL OFS VERTICAL

ee adi
~—}~ CURVE#210' 7
|

___END OF ILLUSTRATION
BUT NOT THE END OF |
THE PROJECT ————}

Ses CURVES (10a ent ;

——J 0.0%

a ier ir | he
PROFILE |
ocstekeneh |

T
|
|

SGUVA 918N9

Fic. 4.—(Continued)

cubic-yard unit to fill 8 varies from 435 to 1,175 feet.
But this cut offers a grader loop varying in average
length from 150 feet for the top three feet to over 420
feet at the bottom. At the top the grader loop will be
short and the production low. If the top of this cut
is placed at the far end of the fill, the low output at
the grader and the long haul tend to offset each other,
with the result that only 12 wagons will be required
in order to maintain an adequate supply at the
grader. If thisis done, the bottom of the cut will fall
at the near end of the fill, and for placing it here 7
wagons will be required. If this process is reversed,
the aly of the cut being placed at the near end of the
fill, only 6 wagons can be used, while in placing the ma-
terial from the bottom of the cut at the far end of the
fill 16 wagons could be utilized. If the wagon train
consists of, say, 10 wagons, 30 per cent of the wagon
time would be lost in inet the close-in material, and
the grader would be idle about 17 per cent of the time
in placing material at the far end of the fill under
the first scheme of operation. If the second scheme of
operation were adopted, 40 per cent of the wagons
would be idle while the material close in was being
placed, and the grader would be idle about 37 per cent
of the time while material was being placed at the
far end of the fill. The advantage of the first
arrangement is clear. ‘There is no way of determining

oints of this kind by rule of thumb. Therefore the
field superintendent often overlooks them. They are
clear enough, however, when the mass diagram and the
profile are thoughtfully scrutinized.

This is only one of the many illustrations which
could be given to show that the mass diagram on work
of this kind offers a logical means of controlling field
operations, just as it offers the proper basis on which
to study a project prior to selecting the outfit best
suited to economical work on it. Another illustration
of the usefulness of the mass diagram in controlling
elevating grader work is found in fills 6 and 6a (Fig. 2),
which are built from cuts C and D. In this case the
mass diagram indicates the movement of approximately
5,300 Rabie ards of material between balance points
6 and 7. ‘There is a considerable excess of material—
about 1,200 cubic yards—originating in cut C which
must be hauled to some point beyond cut D. ‘There are
approximately 250 cubic yards in a small fill between
cuts C and D, which for the purpose in hand is of no
consequence, and some 4,100 cubic yards originating
in cut D which must be placed in fill 6a. The mass

diagram indicates an average haul of 480 feet for this
latter material. If to this is added 50 feet for wagon
manipulation, the average wagon travel becomes 530
feet. As against this the average wagon travel for the
1,178 cubic yards originating in cut C is 1,760 feet, if
this material is hauled to the far end of fill 6a. If,
however, this material is placed at the near end of fill
6a the wagon haul is reduced to 1,420 feet, and by so
doing the average wagon travel on the material taken
from cut D is extended to 630 feet. This illustration
shows that contractors can often improve output by
studies of the details of the work. At current bid
prices on this sort of work (about 25 cents per cubic
yard) the gain in daily production with a 10-wagon
outfit would be worth nearly $16, as shown by Table 2,
which is a saving well eet while.

TABLE 2.—Comparison of production under two methods of working
cuts C and D (Fig. 2) with a 10-wagon outfit (average management)

|
| Scheme A Scheme B
| od Naty pots. Tae
Wagons Days Wagons! Days
Material | Quan- Te- Pro- | work re- | Pro- | work
from cut tity quired |duction| re- | quired duction) re-
Haul | for 100 | with | quired | Haul} for 100 | with | quired
percent; 10 percent) 10 |
pro- | wagons pro- | wagons
duction | duction
he SEAR ae oe ee =
Cubic Per jeer
yards | Feet |Number| cent |Number| Feet Number cent | Number
(Gye ae 1,178 |1, 760 23 44 2.7 |1,410 1 3 | 2
1B ere ae 822 | 660 9 100 0.8 | 755 | 10 | 100 0.8
A is ere 1,000 | 600 9 100 1.0 | 685 | 9 100 | 1.0
Dasa a Rere aa 1,000 | 500 8 100 1.0 | 620 9 100 1.0
‘LA ee Be se 1,000 | 415 df 100 TRON) 625 8 | 100 | 1.0
10 Pr ne, 350 325 6 | 100 | 0.3 | 470 | a 100 0.3
AL OGelillet5; 360)g ease seen ee See lea GRSO 124 set yea Jaen = ee, | 6.3
| |
Average daily production: Cubie yards
Schomé Bi 225 Sp lie 2 eee ne See Se oes ee ek 850
SGherne Ae eee kes eee eee ees een ee ee ee Pe 787
(Cy Ghose, ee, hee See Ce ae See, Eee ees he a 63

At 25 cents per cubic yard, value of increased daily output—#3 X.25=$15.75.

A wide-awake superintendent can sometimes save
team time by using a double dump. This is of ad-
vantage only when a fill contains yardage that is within
the haul limit of his outfit and other yardage that is
outside of this limit. A 10-team outfit, with average
management, can keep the grader busy up to a wagon-
travel distance varying from 600 to 850 feet, depending
on the length of cut from which the loads are being
secured. As an illustration, suppose the mass diagram

64.

QUANTITIES - CUBIC YARDS

BPS BP6

BPI BR2 BR3 B.P4 Ae : BR7 oe
CUT 0.0 O 202 880 1100809664535 O 152 200 22 00 O te) 0 ie} 91 240 250 16! 536024115 1045 2185 850 18 0 0 00 43 70 248 347 ISI 114

FILL+15% 300493 1060 138.0 0 010 24 324 187 173 490 ai56 753 727590 4373201168 146 241 491481530. 0 O 70 454 2530 756300158 313 310 84 0 0]0
>
CUT A | [cul C7
i Mas Als | VERTICAL + } ; 4 + =200' | so] VERTICAL
VERTICAL AVERAGE LENGTH OF CUT= 200 oe
50.00% Ts. | 299g RYO CURVE=250._ 7 VERTICAL | *2-q7% | CURVE:250
oot aay son ee 0.0% 5 ze } VERTICAL—> t CURVE*250 40% 5
288 VERTICAL | VERTICAL Ney) 9 EL 27 Fines] CURVE:250/ 8 0.00%| |
CURVE:150 CURVE=100' JA see al a en Ie
| MI 7
SH la= 260
NGTH OF CUT 350° | oe ot ~ Bx 80 SCALE-
2000 Ruiiee aN e 7 — PROFILE Ay c= 310 | MASS DIAGRAM-VERTICAL 1000 CU. YDS
A=560 SAF 3a
| B= 50’ A TO THE DIVISION.
1000 me: Z C610 '~BORROW.——— 3052 CU.YDS. | PROFILE-VERTICAL 10 FEET 10 THE 3000
w | b ee SSE aoe e (HORIZONTAL 100 FEET. TO THE
| AVERAGE HAUL 400 x
= 00 ee + DIVISION. 2000
Ss — |NTERNAL BALANCE —>1 1000
a 1000 THORAC Uae =400'
= A= AVERAGE HAUL WITH ELEVATING GRADER See ey CTRL ae le ae
NG ceace FOR YARDAGE INVOLVED of eS Ld og
2000 Sie] —} PLUS WAGON MANIPULATION = y es a ee
aes ae 330] _ CTNERAGE WAGON TRAVEL FOR YARDAGE INVOLVED = a
3000 te A® 330, | X-y= AVERAGE HAUL LINE — 4—MASS | DIAGRAM ] A= 370. 1000
= _50 B= 50' | Y
| C= 380 | |. | OBS 2000
25 30 35 40 45 50 55

STATIONS

Fic.¥5.—Second re-design of sample grading project, illustrating how hauls may be further reduced by use of borrow pits

indicates that the current day’s work involves an
average wagon travel of 350 feet. Six wagons are re-
quired to keep the grader busy, and if eight are sent
out the time of two will be wasted. If under such con-
ditions enough wagons are diverted to a longer haul,
so that the proper rate of wagon supply is maintained,
the time of the two wagons can be saved. <A study of
the time-distance graph for wagons (the time-distance
graph will be discussed in the third part of this article)
will show how many wagons must be diverted if this
method of operation is to be successful. When this is
done, however, the superintendent must use consider-
able care to insure that the long-haul wagons do not
become bunched, as bunching will largely obliterate the
benefit to be derived. The dumping at the long-haul
dump need not be given much supervision as it may
be so handled that subsequent operations will cover
work of this kind and correct any careless placement of
material.

The mass diagram may also be made to give a picture
of each day’s work and so to assist the contractor by
showing how much material hehasplaced. How thiscan
be done is shown in the mass diagram for fill 5 (Fig. 2).
Once the mass diagram is in hand all that the contractor
needs to know is the distance completed in order to
determine the yardage he has placed with considerable
accuracy. This is a valuable control and one that
should not be overlooked.

POOR DESIGN REDUCES ELEVATING GRADER OUTPUT

The foregoing illustrations indicate some of the prob-
lems a contractor faces in his effort to operate an ele-
vating grader outfit with maximum efficiency. They
show that the mass diagram is a valuable guide to
sroper bidding and also in the conduct of the work.

ut they also show clearly that the highest degree of
economy may be impossible unless the road is designed
with that end in view. The profile shown in Figure 2
represents a decidedly poor design for elevating grader
construction. The essence of economical design for
this type of equipment is that the cuts and fills shall be
so related in yardage and in the distance between them
that a reasonable wagon train can keep the elevating
grader operating at or near full capacity all the time.
This means that variations in haul should be kept
within a reasonable range. A design which produces
a succession of long and short hauls, such as are found
in fills 1, 2, 3, and 4 of Figure 2, violates the first prin-
ciple of economical elevating grader operation: First,

because the short cuts reduce the rate of output of the
grader; second, because some of the hauls are so lon

that no reasonable wagon train can handle the ful
output of the grader; and third, because other hauls
are so short that the wagon train can work but a frac-
tion of the time with the grader working at full speed.
More nearly correct treatments of this section of high-
way are illustrated in the redesigns shown in Figures
4 and 5.

In preparing these modified designs it has been as-
sumed that local conditions govern the height of the
fills. These have, therefore, been left approximately
at the same height as in the original design, and the
modification in the grade line has been limited to a
readjustment of the cuts in order to secure more nearly
uniform hauls. Cut depths have been freely altered
and vertical curves have been standardized by the
adoption of a uniform radius of curvature of approxi-
mately 5,000 feet. No particular effort has been
made to keep the yardage the same as in the original
design, although it is approximately the same. The
purpose is to illustrate certain principles of design, the
employment of which is not in any way dependent
upon the yardage.

The object in presenting the redesign shown in
Figure 4 is to lay emphasis on the manner in which
by careful design the haul on elevating grader projects
can be so adjusted as to improve output and reduce
production cost. In this first redesign it has been as-
sumed that the fills will be built entirely from the cuts.
Obviously this assumption limits the reduction of the
maximum haul to about half the distance from center
to center of cuts, yet even with this limitation it is
possible materially to reduce the wagon travel. Under
the original design only 42 per cent of the material could
be moved with a wagon travel of less than 600 feet,
and 35 per cent involved a travel of over 900 feet.
Under the first redesign (Fig. 4) 59 per cent of the ma-
terial can be handled with a wagon travel of less than
600 feet and only 8 per cent requires a travel of over
900 feet. The haul of this latter material is imposed
by the distance between cuts, and as already stated
it can not be reduced under the system of design in use.

PRODUCTION COST REDUCED 11 PER CENT BY FIRST REDESIGN

That the first redesign is an improvement from the
standpoint of the contractor will be apparent without
much explanation. Under the redesign economical
operation requires nearly as many wagons as under the

B.P.10 All
161 S89 156 WTS 900 382 69 ep 6 9: '¢

ies

- 1
AVERAGE LENGTH OF CUT#=350
—

0 63 (21

398

128
297

DIAGRAM

STATIONS

Fic. 5.—(Continued)

original design, but because much less work has to be
done over the long wagon travel distances the cost of
production is reduced about 11 per cent. At the pre-
vailing bid price for work of this kind (25 cents per
cubic yard) this difference, if obtainable on projects
generally, should in the long run mean a reduction of
from 2 to 214 cents per cubic yard in the price paid by
the State for elevating grader work. Whether on any
large percentage of projects a similar saving could be
made by redesign has not been fully investigated. This
is, however, of less importance to the designer than the
fact that it can be made on some projects.

To the contractor such a saving is of vital concern
for his money is at stake. To him the original
design and the redesign present a concrete example
of how design often affects his profit by introducing
a wide range of wagon travel; and the comparison of
the two designs should explain why two jobs in which
topographic conditions are similar may return dif-
ferent percentages of profit or loss. The writer
has more than once been told by distracted con-
tractors that it has been impossible to obtain proper
production on the job in hand though jobs in similar
territory had on other occasions yielded a fair profit;
but never has there appeared to be any appreciation of
the fact that the fault might le in the design rather
than in the way in which the job had been handled or
that the size of the outfit might have affected the cost
of handling the work.

BORROW PITS REDUCE COST BY ELIMINATING LONGER HAULS

Figure 5 shows a second redesign. Under this design
long haul has been further reduced by the use of borrow
pits. In the Mississippi Valley it 1s often possible to
obtain stripping rights, i. e., the right to take material
to a certain depth, generally a foot or two, from abut-
ting property. The advantage of this practice hes in
the fact that the grader run can readily be made such
as to yield 100 per cent production at the grader, while
at the same time the haul can be kept within the ca-
pacity of a normal wagon train.

Whether to use the method or not, from the stand-
point of the State, depends on the saving likely to result
and the cost of the rights. From the standpoint of the
contractor its desirability is apparent as its use reduces
the longer hauls imposed in the first redesign by the
distance between cuts. Under this design only seven
wagons would be required for the most economical

prosecution of the work, 87 per cent of the material
would be hauled less than 600 feet, no material would
require wagon travel in excess of 900 feet, and the pro-
duction cost would be 20 per cent less than under the
original design. A condensed comparison of the three
designs is given in Table 3; the methods used in deriving
the results shown will be explained in Part 3 of this
series of articles.

TABLE 38.—Compdrison of cost of three designs using various
wagon trains

First redesign} 29,887 | 14.1
| | \ |

1 Based on standard daily production of 1,000 cubic yards.

Minimum production cost:
Original design, 15.8 cents with 11 wagons.
First redesign, 14.1 cents with 9 wagons.
Second redesign, 12.7 cents with 7 wagons.
Difference in production cost=8.1 cents, or about 20 per cent.

PRODUCTION COST IN RELATION TO HAUL

The relation of haul to cost may be further illus-
trated by a very general production cost statement.
Under the wage scales prevailing in the Mississippi
Valley and contiguous territory the fixed costs of
operating an elevating grader are not far from $80 a

day. The cost of hauling is about $5 per team per
day. These costs cover field pay roll, feed for the

teams, cookhouse losses, and minor repairs only and,
for the purposes in hand, will be referred to as the
production cost. The contractor has many other

costs to meet, such as the costs of office overhead,
bond, financing, getting onto the job, depreciation,
ete., all of which are presumably included in the bid
price, but these are largely BES of production
cost and should not be include

factors affecting production cost that are under con-
sideration.

Accepting the above production costs as a basis of
comparison and assuming the condition of an elevat-
ing grader working in a 450-foot cut and the wagon
supply menue for standard production of 1,000
cubic yards a day at the various lengths of wagon
travel, the costs of production per cubic yard will be
as shown in Table 4.

TasLte 4.—Unit costs of production for standard production from
a 450-foot cut with various hauls

: =
| Daily

| | iets
Feet | Number | Dollars Cents
| 825 6 | 110
500 | 8 120 12
675 10 130 13
850 12 140 14
| 1, 025 14 150 | 15

Average rate of increase, 0.6 cent per station.

The table presents, of course, a highly generalized
statement of the costs, but it will serve to show, for
example, that if the wagon travel can be kept down
to a point where an 8-wagon outfit can be appropri-
ately used, production cost will be about a cent a
yard less (bid prices should average about 2 cents
less) than where the wagon travel is such that a 10-
wagon outfit is required. If, with any given wagon
supply, the length of cut is shortened the effect will
be to lower production so that the saving resulting
from a shortening of the haul may in this way be
offset by the reduced output obtainable.

If, on the other hand, the wagon supply is not
adequate, the cost will mount rapidly. Thus, if an
8-wagon outfit (basic cost of production 12 cents) is
working where the wagon travel is 1,025 feet, it will
supply only eight-fourteenths of the necessary num-
ber of wagons; the production will fall, therefore, to
eight-fourteenths of normal, and the cost of produc-
tion will rise to 21 cents.

Two important points should be somewhat clarified
by this analysis. The first of these is that the con-
tractor who undertakes a project with less than the
proper wagon supply will generally find that bis produc-
tion cost is higher than the haul distances prevailing
would normally generate; and the second, that the
injection of occasional long hauls has relatively a more
important effect on production cost than a general
increase in the haul for which provision can be made
in the selecting of the outfit.

To the contractor this latter point is of special
importance in that it shows that bids on overhaul
must be carefully scrutinized. It is customary to take
overhaul on work of this sort at about 2 cents per
station yard. If the station yardage of overhaul is
large, the contractor will be justified in providing a
wagon supply sufficient to care for it properly, and
the price of 2 cents may be sufficient or even excessive,
but more often the overhaul is generated by a few cuts
from which long hauls are required. In such cases it
is not practicable to increase the wagon supply and

, since it is only the:

the output may be so reduced, when operating on
this long-haul work, that the production cost alone
may about equal the price received. In such cases
the contractor loses on his overhaul.

SUPPLEMENTARY USE OF FRESNO MAY SAVE MONEY

In the foregoing discussion it has been assumed
that contractors use an outfit of fixed size. This, in
fact, is the all-but-universal practice. Under this
system team time is lost in considerable amounts
whenever the wagon travel is short, and grader time
is lost whenever a long travel distance is encountered.
There is, however, another method of handling such
work that deserves more consideration than it 1s now
receiving.

It is well known that the fresno can move [dirt on
short-haul jobs about as cheaply as it can be moved by
an elevating grader outfit. This being the case, there
seems to be no good reason why the fresno and the
elevating grader can not be combined with profit when
the conditions warrant. There are a good many angles
to this question, and it is quite impossible to treat all
of them in the short space here available. Briefly,
however, the situation is substantially this: The ele-
vating grader is a wonderfully effective loading mech-
anism; the wagon is perhaps the most efficient haulin
mechanism available for work within its proper field.
As long as these can be kept in balance and efficiently
operated, the cost of producing yardage in place is
probably as low as it can be made with any type of
earth-moving equipment, particularly if the haul is of
any considerable length. However, as the haul ap-
proaches zero there is a short distance, probably not
exceeding 200 feet, in which the fresno can produce
yardage in place about as cheaply as the elevating
grader. For such short hauls the wagon supply of the
elevating grader must be excessive, since it is properly
designed for the longer hauls. On the average project
there is always a certain amount of work to do which is
well within the field of the fresno, and there are hauls
which, while clearly within the field of the elevating
grader, are shorter than the average for the project
and are capable of handling with less than the full outfit
of teams. If, whenever this condition obtains, the
teams not needed by the grader are shifted to fresnoes,
whatever yardage is moved by the latter will represent
a clear gain in production.

The field of competition again turns against the
fresno when the distance becomes so short that the
elevating grader can cast the material into place, as-
suming, of course, that no wagons are kept ie during
the casting operation and that the ditches are not so
deep that the output of the grader will be sharply
reduced by the tilting of the machine. But the fact
that is apt to be overlooked in considering the relative
cost of short haul and casting is that so long as the
contractor must maintain his teams (including drivers)
he can gain nothing by casting unless he thereby in-
creases his output per hour. The possibility of increas-
ing output by casting lies in the fact that the time lost
in wagon exchange is saved, but this saving is not
always a net gain, because a certain amount of time
must always be lost in resting the grader stock. Asa
matter of fact, when the grader is drawn by a tractor
or by 20 horses the output generally is somewhat in-
creased when casting, but if only 16 horses are used
the aggregate of the rest periods is generally about as
great as the time lost in wagon exchange, and no par-
ticular advantage accrues.

Under these general conditions if a contractor, de-
siring a high average rate of output at the lowest
ossible cost, instead of selecting a wagon train on the
asis of the average haul would select it on the basis
of the longer hauls and then plan to send out with the
wagons each day only those teams which can be worked
to Papacity, using the balance in taking out ditches
and short-haul cuts with fresnoes, he would find that
under practically all circumstances his grader could be
worked to pee and his extra teams, instead of
spending much of the time waiting to be loaded, would
be producing yardage ata profitable margin. In discuss-
ing this scheme of operation with contractors two objec-
tions to it have been raised: First, that teamsters operat-
ing wagons do not like to transfer to fresnoes and, sec-
ond, that the standard 14-yard wagon requires only
two horses while the 4-foot fresno requires three.
There is a valid answer to both objections. To the
first there is the answer that employers generally find
no difficulty in enforcing conditions which are clearly
set forth when men are employed. The other may be
met with the blunt statement that the 14-yard wagon
has no ees on elevating grader work and should be
replaced by the more efficient 2-yard wagon. The
2-yard wagon requires three horses, but day in and
day out it will haul 50 per cent more than the 114-
yard wagon. Where it is used there will be no diffi-
culty in shifting the 3-horse teams to 4-foot fresnoes.

TWO-YARD VERSUS ONE AND ONE-HALF YARD WAGONS

The desirability of using 2-yard instead of 114-yard
wagons needs no very extended defense. In the first
place, as noted above, 50 per cent more yardage is
secured per load at the expense of only one extra horse.
At the present time it costs about 70 cents each per day
to maintain stock. With drivers at $3.50 the cost to a
contractor of maintaining a 2-horse team on the job is
in the neighborhood of $4.90 a day. As compared
with this, the cost of maintaining a 3-horse team is
about $5.60. Thus, with a 14 per cent increase in cost
a 50 per cent larger load can be moved, and this is an
advantage that no contractor can afford to overlook.
Moreover, the actual load per horse is slightly less
when three horses are used on a 2-yard wagon than
when two horses are used on a 14-yard wagon, because
while the pay load per horse is about the same, there
is no important difference in the internal frictional
resistance of the two sizes of wagons.

In addition to this saving in the hauling cost, which
is a relatively large one, the larger normal grader output
must also be considered. This larger output is due to
the smaller number of wagon-exchange periods for a
given yardage. As by its use only about two-thirds as
many waits between loads are required, the 2-yard
wagon, used with normal efficiency should produce at
least 10 per cent more output than the 14-yard
wagon.

The one valid objection which has been raised to the
use of the larger wagon is that in soft ground it tends to
mire down a little more than the 14-yard wagon.
This can be avoided by supplying the larger wagon
with a tire of proper width.

It is impossible to recommend the use of wagons
larger than the 2-yard size, because when more than
three horses are used there is difficulty in getting
under the belt quickly. There is also some difficulty
in maneuvering at the dump. These problems are
not, however, of any consequence where three horses
are used, and the evident success of those outfits now
using 2-yard wagons offers concrete evidence that the
advantages here noted are being secured by at least a
few progressive contractors.

The natural deduction from these facts is that if the
contractor desires to operate as profitably as possible,
and at the same time to reduce the element of risk in
his elevating grader work to a minimum, he will study
the various elements of his job with care and will pro-
vide enough wagons that he can keep his grader work-
ing at capacity. There are industries which to-day
make all of their profit out of the use of materials
formerly wasted. The situation of the elevating
erader contractor is somewhat analagous in that as
his work is now conducted team time is wasted in
large amounts. One way of utilizing waste team time
has been mentioned. Others could, no doubt, be sug-
gested. The point is that every time a team stands
idle when it could be made to produce something
valueislost. Salvaging this value will prove profitable
to any contractor who will undertake it seriously and
methodically. If, to his efforts to salvage lost time he
will add a serious study of those elements in this sort
of work which are responsible for its present specula-
tive aspects, particularly the element of haul, he should
have little trouble in avoiding the financial troubles

so often encountered by those operating in this
field.

(Continued from p. 58)

that maintenance costs on macadam roads are approxi-
mately one-sixth as much per mile per vehicle as those
on gravel roads, and in individual cases much less than
this amount.

Even estimating 1,000 vehicles per day instead of 500
as the capacity of a gravel road, reference to the 1930
forecast map (Fig. 10) will indicate that a considerable
mileage of gravel roads on the Maine primary system
Beeald be reconstructed with more durable surfaces
within the next six years.

On the basis of a maximum capacity of 1,000 vehicles
per day for gravel-surfaced highways, the following pro-
gram for the improvement of Maine highways is sug-
gested for the period 1925 to 19380:

1. Construction of high-type pavements on the heavy-
traffic routes.

2. The heavy-traffic routes included in the suggested
improvement program, listed below, are divided into
three groups based on density of traffic, the type of
traffic on each highway, and the urgency of the need for
immediate improvement.

3. It is suggested that the routes in Group | be im-
proved first, those in Group II second, and those in
Group III last.

4, Because of the greater total traffic as well as the
larger number of motor trucks per day on the highways
in Group I, high-type pavements are suggested for this
group.

‘ BeOn the basis of Maine construction and mainte-
nance experience it is believed that bituminous mac-
adam, of the type now being constructed in the State
will adequately serve the present and future traffic on

the highways included in Groups II and III for the ex-
pected life of the bituminous-macadam type of con-
struction.

6. In the selection of the surface type for highways
in Groups II and III consideration should be given to
the present type of surface on sections of the highways
included in these groups.

7. Following is a description of the highways included
in each group:

Primary system

Group I:
Kittery— Portland—Brunswick.
Portland—Auburn—<Augusta.
Augusta— Gardiner.
Waterville— Fairfield.
Bangor—Oldtown.

Group II:
Brunswick—Gardiner.
Brunswick—Belfast.
Brunswick—Auburn.
Augusta— Waterville.
Fairfield—Bangor via Newport.
Bangor—Ellsworth.
Waterville—Oakland.

Group III:
Belfast—Bangor.
Bangor—Ellsworth via Orland.
Ellsworth—Bar Harbor.
Fairfield—Skowhegan.
Wells—Berwick.
Portland—Bridgton—State line.
Gray—Norway.
Auburn—Farmington—Strong.
Newport—Dover.
Perry—Calais.
Houlton—Presque Isle—Van Buren.

Secondary system
Group I:
Portland— Westbrook.
Group IT:
Auburn—Mechanic Falls.
Wells—Sanford.

Budget requirements for this period can be estab-
lished by computing the mileage of each type to be
constructed (total mileage of designated routes less
improvements already made) and estimating the costs of
such construction. If estimated available revenues over

the period are not sufficient to meet such expenditures,
the possibility of a bond issue to be retired from funds
derived from an increased gasoline tax is suggested.

It is estimated that a gasoline tax of 1 cent per gallon
will yield approximately $4,500,000 during the six-year
period 1925 to 1930, inclusive. An increase of this
tax from 1 to 3 cents per gallon would provide approxi-
mately $9,000,000 in additional revenue.

During this same six-year period license fees, assum-
ing no change in fees, may be expected to yield approxi-
mately $17,000,000, making a total of $21,500,000 from
license fees and a gasoline tax of 1 cent per gallon, or
a total of approximately $30,000,000 from license fees
and a gasoline tax of 3 cents per gallon.

NEW TESTING: DEVICES I DEVELOPED

Three new testing devices for the use of the highway
engineer have been developed by the Division of Tests
of the Bureau of Public Roads.

A test for the consistency of concrete in the field has

been devised as a substitute for the slump test, which
is not particularly reliable under all conditions. The
method is particularly adapted for concrete paving
and other work in which a relatively dry consistency
can be employed. It is based upon the principle that,
within working limits, the consistency of freshly mixed
concrete is proportional to the weight which will be
retained upon a plate of given diameter when the con-
crete is deposited on it in a standard manner. The
device consists of a truncated cone large enough to
hold about 75 pounds of wet concrete, supported by an
angle-iron frame above a circular plate 15 inches in
diameter, which in turn rests upon a spring balance.

The method of testing is as follows: The apparatus
is placed upon the subgrade and the cone is filled with
concrete immediately after the batch has been de-
posited by the bucket. Immediately after filling the
cone a removable slide at the bottom is withdrawn
and the concrete flows out upon the plate. If the
mix is either very dry or very wet, a larger quantity
will roll or flow over the edges of the plate than if it
is moderately dry. The plate is supported above the
spring balance by two cams which take the weight
of the concrete off the spring until it has all been de-
posited. By turning a handle which revolves the sup-
porting cams the concrete upon the plate can then be
weighed. It has been found that for a 15-inch plate
the usual variations in the amount of water in a
1:2:3 paving mix will cause a difference in weight
of from 20 to 50 pounds. Experiments have indicated
that for machine-finished work the proper consistency
to use is one which will give the greatest weight
of concrete retained upon the plate. For hand-fin-
ished work a mix slightly wetter than this would
probably have to be used. This device has been
tried on actual construction and it appears to be
of practical value. A more complete description of
the process, together with test data illustrating the
use of the apparatus, will appear in an early issue of
Pusxio Roaps.

Work has also been carried forward on a device
designed to register the intensity of pressure used
during the molding of Portland cement mortar bri-
quettes. Considerable latitude has always been allowed
operators in regard to this detail of cement testing,
resulting in quite appreciable variations in manipu-
lation, which undoubtedly affect test results. The
device consists of a small weighing platform approxi-
mately 15 inches long and 4 inches wide, large enough
to hold a glass plate and a three-gang briquette mold.
The device is so arranged that an electric contact is
made when a certain pressure is exerted on the briquette
by the operator, lighting a white light in the front of
the apparatus. Another contact, which when made
shows a red light, may be set for a pressure beyond
which the operator should not go. In determining
whether an operator is using the proper pressure it is
only necessary for him to mold a set of briquettes
on the weighing platform and to note whether the
pressure he exerts is sufficient to light the white light
but not the red light. Both of the contact points
are adjustable so that any pressure within working
limits may be recorded.

GS,

particularly interested.
nor to send free more than one copy of any publication to any one person.

ROAD PUBLICATIONS OF BUREAU OF PUBLIC ROADS

Applicants are urgently requested to ask only for those publications in which they are

The Department can not wndertake to supply complete sets
The editions

of some of the publications are necessarily limited, and when the Department’s free supply
is erhausted and no funds are available for procuring additional copies, applicants are
referred to the Superintendent of Documents, Government Printing Office, this city, who

has them for sale at a nominal price, wnder the law of January 12, 1895.

Those publica-

tions in this list, the Department supply of which is exhausted, can only be secured by
purchase from the Superintendent of Docwments, who is not authorized to furnish pub-

lications free.

ANNUAL REPORT

Report of the Chief of the Bureau of Public Roads, 1924.

No.

105.
F136.
220.
257.
*314.
*347.
*370.
386.
387.
388.
390.
*393.
407.

*463.
*532.

*537.
*583.
*586.

*660.
*670.

*oOT,
*704.
*724.

*107¢.
*1132.

DEPARTMENT BULLETINS

Progress Report of Experiments in Dust Prevention
and Road Preservation, 1913.

Highway Bonds. 20c.

Road Models.

Progress Report of Experiments in Dust Prevention
and Road Preservation, 1914.

Methods for the Examination of Bituminous Road
Materials. 10c.

Methods for the Determination of the Physical
Properties of Road-Building Rock. 10c.

The Results of Physical Tests of Road-Building Rock.
15ce.

Public Road Mileage and Revenues in the Middle
Atlantic States, 1914.

Public Road Mileage and Revenues in the Southern
States, 1914.

Public Road Mileage and Revenues in the New
England States, 1914.

Public Road Mileage in the United States, 1914. A
Summary.

Economic Surveys of County Highway Improvement.
35c.

Progress Reports of Experiments in Dust Prevention
and Road Preservation, 1915.

Earth, Sand-Clay, and Gravel Roads. 15c.

The Expansion and Contraction of Concrete and
Concrete Roads. 10c.

The Results of Physical Tests of Road-Building Rock
in 1916, Including all Compression Tests. 5c.

Report on Experimental Convict Road Camp, Ful-
ton County, Ga. 25c.

Progress Reports of Experiments in Dust Prevention
and Road Preservation, 1916. 10c.

Highway Cost Keeping. 10c.

The Results of Physical Tests of Road-Building Rock
in 1916 and 1917. 5c.

Typical Specifications for Bituminous Road Mate-

rials. 10c. ;
Typical Specifications for Nonbituminous Road
Materials. 5c.

Drainage Methods and Foundations for County
Roads. 20c.

Portland Cement Concrete Roads. 15c.

The Results of Physical Tests of Road-Building Rock
from 1916 to 1921, Inclusive. 10c.

No.

REPRINTS

Vol.

Vol.
Vol.

Vol. 10, No.
Vol. 11, No.

. *338. Macadam Roads.

. *727. Design of Public Roads.

1216. Tentative Standard Methods of Sampling and Test-
ing Highway Materials, adopted by the American
Association of State Highway Officials and ap-
proved by the Secretary of Agriculture for use in
connection with Federal-aid road construction.

1259. Standard Specifications for Steel Highway Bridges,
adopted by the American Association of State High-
way Officials and approved by the Secretary of
Agriculture for use in connection with Federal-aid
road construction.

1279. Rural Highway Mileage, Incomes and Expenditures,
1921 and 1922.

DEPARTMENT CIRCULAR

. 94. TNT as a Blasting Explosive.

FARMERS’ BULLETINS

oC.
*505. Benefits of Improved Roads. 5c.

SEPARATE REPRINTS FROM THE YEARBOOK

5c.
*739. Federal Aid to Highways, 1917.
*849. Roads. 5c.

OFFICE. OF PUBLIC ROADS BULLETIN

*45, Data for Use in Designing Culverts and Short-span
Bridges. (19138.) 15ce.

OFFICE, OF THE SECRETARY CIRCULARS

49.
59.

63.
ap

DCs

Motor Vehicle Registrations and Revenues, 1914.

Automobile Registrations, Licenses, and Revenues in
the United States, 1915.

State Highway Mileage and Expenditures to January
PeLoLe:

Width of Wagon Tires Recommended for Loads of
Varying Magnitude on Earth and Gravel Roads.
5¢

Automobile Registrations, Licenses, and Revenues in
the United States, 1916.

Rules and Regulations of the Secretary of Agriculture
for Carrying out the Federal Highway Act and
Amendments Thereto.

FROM THE JOURNAL OF AGRICULTURAL
RESEARCH

Effect of Controllable Variables Upon
the Penetration Test for Asphalts and
Asphalt Cements.

Apparatus for Measuring the Wear of
Concrete Roads.

A New Penetration Needle for Use in
Testing Bituminous Materials.

Toughness of Bituminous Aggregates.

Tests of a Large-Sized Reinforced-Con-
crete Slab Subjected to Eccentric Con-
centrated Loads.

73.
161.

17) D=2.

ONO:

OWNO:
5, No.

20, D-4.
24, D-6.

Dla
10, D-15.

* Department supply exhausted.

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Full text of "Public Roads: A Journal of Highway Research, Vol. 6, No. 3"

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