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September 1985
Vol. 49, No. 2
A U apy
Sen
a
‘
|
te Public Roac
US. Department
of Transportation
A Journal of Highway Research and Development
Federal Highway
Administration
U.S. Department of Transportation
Elizabeth Hanford Dole, Secretary
Federal Highway Administration
R.A. Barnhart, Administrator
U.S. Department of Transportation
Federal Highway Administration
Washington, DC 20590
Public Roads is published quarterly by the
Offices of Research, Development, and
Technology
David K. Phillips, Associate Administrator
Technical Editor
C.F. Scheffey
Editorial Staff
Cynthia C. Ebert
Carol H. Wadsworth
William Zaccagnino
Advisory Board
R.J. Betsold, S.R. Byington, R.E. Hay, George
Shrieves
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Public Roads
A Journal of Highway Research and Development
September 1985
Vol. 49, No. 2
COVER: Old concrete pavement is broken, crushed, and recycled as aggregate
into new concrete pavement to widen and improve I-90 and |-94 near Madison,
WI.
IN THIS ISSUE
Articles
The Use of Recycled Portland Cement Concrete (PCC) as Aggregate
in PCC Pavements
by Stephen W:, Forster 2m cee ee ote eee eee eee ne o7
Research Needs in Asphalt Technology
by E.. Ts Harrigam2 ced t a. open teen ero ens esl ee eta ee 43
Limited Sight Distance Warning for Vertical Curves
by Mark Freedman, L.K. Staplin, and Lawrence E. Decina............ 46
Netsim for Microcomputers
by Scott. Wes ibley sata. « crcecmelc adeuentte betes crt aa suee tees telne ne aaa 54
Departments
Recent Research Reports .........
New Researchin Progress.........
Public Roads, a Journal of Highway Research
and Development, is sold by the Super-
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Printing Office, Washington, DC 20402, for $12
per year ($3 additional for foreign mailing) or
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Contents of this publication may be
reprinted. Mention of source is requested.
ATT ~T
sizcaid =v
The Use of Recycled Portland Cement
Concrete (PCC) as Aggregate in
PCC Pavements
by
Stephen W. Forster
Introduction and
Background
Economic considerations are the
primary reasons for recycling portland
cement concrete (PCC) as aggregate
in PCC pavements, although environ-
mental benefits often are derived as
well. In some areas of the United
States there is no supply of virgin
aggregate and recycling is the only
viable economical solution. In other
areas, new aggregate is inaccessible,
either because of the high value of
land or because zoning constraints
prevent the opening of pits or
quarries. In some highly developed
urban areas, it is less expensive and
more environmentally acceptable to
re-use the PCC than to dispose of it.
Therefore, when a PCC pavement
will be removed before a new pave-
ment is placed, the project is a prime
PUBLIC ROADS ® Vol. 49, No. 2
candidate for recycling. The old
pavement serves as a source of
aggregate in the new concrete, and
the need and expense of disposing of
the material removed are eliminated.
Further, if the project is large enough
for an onsite aggregate plant, the
materials’ transportation costs are
reduced.
Results of a 1971 survey conducted
by the Texas State Highway
Department and the Texas Trans-
portation Institute indicate that most
States gave little consideration to
recycling existing pavement material
for any use other than unstabilized
base courses. (7, pp. 128-133) 1 PCC
removed from a roadway usually was
disposed of in landfills or used as
‘Italic numbers in parentheses identify ref-
erences on page 42. Page numbers in paren-
theses refer to reference 1.
erosion control in drainage ditches.
Because of the increasing cost of
natural resources and energy, this
attitude has changed.
Initial proposals to use recycled PCC
as concrete aggregate material
generated a number of questions.
First, how does the quality of the
new concrete containing the recycled
material compare with the old
concrete and with new concrete
made with natural aggregate? Does
the crushed concrete make good
aggregate? How can the reinforcing
be easily removed? Is recycling for
aggregate an economically viable
alternative? These questions and
many others concerning PCC
recycling have been answered by
subsequent research. This article
reviews research on the use and
properties of the recycled material as
aggregates in PCC.
In June 1977, the Federal Highway
Administration (FHWA) established
project 22 on PCC and asphalt pave-
ment recycling under its National
Experimental and Evaluation Program
(NEEP). Forty-two States participated
in the project, which has now been
integrated into Demonstration Project
No. 47 (DP47), Recycling Portland
Cement Concrete, and DP39, Asphalt
Pavement Recycling. The initial DP47
project report was the reprinting of
an lowa Department of Transporta-
tion report on an early recycling proj-
ect. (2) Since then, several States
have conducted recycling projects un-
der DP47, and States continue to
show interest in participating in
DP47.
In September 1981, a national
seminar on PCC recycling and
rehabilitation was sponsored by
FHWA and conducted by the Trans-
portation Research Board (TRB).
(Jas)
Recycling Categories
PCC pavement recycling may be
grouped into three categories. First,
surface recycling involves milling or
grinding the pavement surface
(approximately the top 1 in [25.4
mm]) to remove surface deterioration,
restore rideability, and improve
surface friction. Because the removed
material usually is quite fine and rela-
tively small in quantity, it typically is
not used as concrete aggregate.
Second, inplace recycling involves
crushing the old pavement and
combining it with the existing base or
subbase material to support a new
pavement. Third, plant recycling
involves breaking up the existing PCC
pavement, taking it to a crushing
plant where it is crushed and sized,
and finally incorporating the resulting
aggregate material into a new PCC
mixture. This article focuses on this
use of the old concrete as aggregate
in new PCC.
38
Properties of Recycled PCC
Aggregate
Aggregate tests
In an early laboratory study of
recycled PCC, the properties of an
aggregate made from crushed
concrete containing chert gravel
(coarse) and natural sand (fine) and a
second aggregate made from crushed
concrete containing limestone
(coarse) and natural sand (fine) were
compared with natural aggregate.
The material then was incorporated
into new concrete mixes for further
comparisons. (4) Table 1 shows the
results of absorption and specific
gravity tests.
Visual inspection of the crushed
concrete indicated a good particle
shape. The fine aggregate produced
did not meet the normal gradation re-
quirements but was used in the
concrete mixes discussed under the
section, Concrete tests, below.
A synopsis of studies conducted by
the U.S. Army Engineers Waterways
Experiment Station, lowa Department
of Transportation, Massachusetts
Institute of Technology, Minnesota
Department of Transportation,
Michigan Department of Transpor-
tation, and FHWA concludes that the
aggregate particles produced by
crushing concrete have good shape,
high absorptions, and low specific
gravity compared with natural mineral
aggregates. (7, pp. 128-133)
Table 2 shows the results of a Michi-
gan Department of Transportation
laboratory investigation of a series of
crushed concrete materials compared
with natural aggregate. (7, pp.
144-160) A concrete material that had
been recycled twice also was tested,
and its specific gravity was still lower
(2.11) and the absorption even higher
(8.36 percent) than material recycled
once. These results are predictable
because the percentage of natural
aggregate decreases and the
percentage of lighter, more
Table 1.—Properties of crushed concrete and natural aggregate (3)
Recycled material
Limestone concrete
Chert concrete
Natural material
Chert gravel Crushed limestone
Coarse fraction:
Absorption 4.0-4.3
Saturated surface
dry specific
gravity 2.43-2.44
Fine fraction:
Absorption 7.6-9.0
Saturated surface
dry specific
gravity DSO
3)
to
wal
to
bo
Nn
ine)
2.6 0.8
2.67
Table 2.—Properties of crushed concrete and natural aggregate (/, pp. 144-160)
Natural
Material Material material
recycled once recycled twice Gravel
Coarse fraction:
Absorption 3.43-5.0 8.36 1.02
Bulk specific gravity 2.31-2.40 Dalat AST
Fine fraction:
Absorption 7.17-8.31 = 1.38
Bulk specific gravity Dalia 23 — 2.60
September 1985 © PUBLIC ROADS
absorptive cement paste increases
with each recycling. Interestingly, the
soundness loss of the recycled
material was less (0.9 to 2.0) than
that of the natural aggregate (3.9).
Concrete tests
In the 1973 study, recycled concrete
was mixed with a water/cement ratio
of 0.49, had a target air content of 6
+ 1/2 percent, and a slump of 2 1/2
+ 1/2 in (64 + 13 mm). (4) Concrete
made with recycled concrete as both
coarse and fine aggregate had lower
slumps and higher cement contents
than comparable mixes made with
either all natural aggregate or
recycled coarse aggregate and
natural sand fine aggregate. The
concrete with recycled aggregate had
compressive strengths 300 to 1,300
psi (2.0 to 9.0 MPa) less than the
control concrete with natural coarse
aggregate throughout the period of
testing (up to 180 days). Freeze-thaw
test results differed depending on the
original aggregate. Recycled concrete
containing freeze-thaw susceptible
coarse aggregate performed better as
aggregate in a new concrete than
concrete containing that stone as
coarse aggregate (although whether
the improvement is sufficient to bring
performance to an acceptable level
would have to be judged case-by-
case). Conversely, new concrete
made with recycled concrete
containing an originally freeze-thaw
resistant aggregate performed
somewhat worse than the control mix
with the natural coarse aggregate,
although both mixes performed
acceptably. Finally, volume change tn
response to temperature changes or
increased moisture was similar for the
recycled concrete mixes and the
controls. (4)
PUBLIC ROADS ® Vol. 49, No. 2
The following conclusions were made
about recycled concrete in the
synopsis report (7, pp. 128-133):
e Using crushed concrete as coarse
aggregate did not significantly affect
mixture proportions or workability of
the mixtures compared with the
control mixtures containing natural
aggregate.
e When crushed concrete was used
as fine aggregate, the mixture was
less workable and needed more water
and therefore more cement.
Substituting natural sand for up to 30
percent of the recycled fine aggregate
improved workability to the approxi-
mate levels of a conventional mixture.
e The frost resistance of the concrete
made from recycled aggregates
usually was much higher than the
frost resistance of the control
concrete.
e Using recycled aggregate did not
significantly affect the volume
response of concrete specimens to
temperature and moisture changes.
e Using low-strength, recycled
concrete as aggregate is not detri-
mental to the concrete’s compressive
strength.
e Using water-reducing admixtures to
lower the water content strengthens
concrete mixtures that contain
recycled concrete as aggregate.
The Michigan Department of
Transportation varied the percentages
of recycled PCC in the fine aggregate
to determine the effect on the
mixture. (7, pp. 144-160) The
percentage of recycled bituminous
concrete also was varied in the
mixture to simulate contamination
that would occur in practice.
Mixtures had a water/cement ratio of
0.43, a cement factor of 6 sacks/yd *
(7.8 sacks/m 3), and an entrained air
percentage of 5.5 + 1.5. The results
of this research agree with the
findings previously discussed. (7, pp.
128-133; 4) Because of the harshness
of the recycled fine aggregate, the
slump, and therefore workability, of
the recycled concrete mixtures was
less than that of the control mixture.
Compressive and flexural strengths of
the recycled concrete were slightly
less than those of the control mixture
made with a gravel aggregate but still
exceeded the Michigan Department
of Transportation minimum speci-
fications for pavement concrete.
Recycled mixtures containing small
amounts of crushed bituminous
concrete (such as patches and
unremoved overlay spots) tested
satisfactorily unless they included
crushed bituminous fines. These fines
are almost totally bitumen coated
and, therefore, act as voids in any
strength test of the new concrete.
The recycled concretes had higher
durability factors than the control
concrete.
Special Concerns for
Recycled PCC
Recycled “D” cracked pavement
The possibility of using crushed ‘‘D”’
cracked pavement as an aggregate
material raises the question as to
whether the recycled material will
continue to promote ‘’D”’ cracking or
will the crushing that occurs during
recycling alleviate the problem?
Before using a ‘‘D”’ cracked PCC
pavement on a recycling project, the
Minnesota Department of
Transportation conducted a labora-
tory study to determine the behavior
39
of recycled ‘‘D’’ cracked material
when used as aggregate in new
concrete. (5) A 3 ft (0.91 m) section,
the full width of the candidate pave-
ment, was removed and crushed for
testing in the laboratory. A control
was made with all natural aggregate
and 20 percent fly ash substituted for
15 percent of the cement. The
recycled material passing the No. 4
(4.75 mm) sieve was found to be very
angular, which substantially increased
the water demand to provide
acceptable workability. Mix 1, 100
percent recycled aggregate, required
333 Ib/yd 3 (197.6 kg/m 3) of water
compared with 250 to 260 Ib/yd 3
(148.3 to 154.3 kg/m 3) for the
control. This higher water demand
also increased the cement
requirement. Compressive strengths
were at or above conventional
mixtures, and there was no problem
entraining the necessary air. Based
on these results, three additional trial
mixes were made. One had no fly
ash, one had 10 percent of the
cement replaced by fly ash, and the
third had 15 percent of the cement
replaced by 20 percent fly ash. All the
recycled aggregate used passed the
3/4 in (19 mm) sieve, and 0 to 5
percent passed the No. 4 (4.75 mm)
sieve.
To evaluate the ‘‘D’’ cracking suscep-
tibility, the mixes were freeze-thaw
tested. Compared with concrete
containing the ‘’D”’ cracking natural
aggregate, the concrete with the
recycled concrete aggregate was
more resistant to freeze-thaw action,
and the mixtures with 10 to 20
percent fly ash had a greatly reduced
“‘D” cracking potential. In addition,
the fly ash acted as a plasticizer,
lowering the amount of water
necessary to make the mix workable.
40
Based on these laboratory results,
U.S. Rte. 59 in Minnesota was recon-
structed using recycled concrete as
coarse aggregate in the new
concrete. The specific gravity of the
recycled coarse aggregate was 2.41,
and its absorption was 4.4 percent.
Natural sand was used as the fine
aggregate, and 20 percent fly ash
was substituted for 15 percent of the
cement. Average core strength on
the concrete was 4,590 psi (31.6
MPa) after 60 days. The minus No. 4
(4.75 mm) recycled material was used
in the base course as a stabilizing
material.
Salt content of recycled pavement
Because large amounts of rock salt
are used as a deicer on Michigan
highways, the sodium chloride (NaCl)
content of recycled PCC aggregate
material was examined. (7, pp.
144-160) The NaCl content of the
recycled material was less than 2
Ib/yd * (1.2 kg/m 3) compared with
Michigan’s critical NaCl level of 4
Ilb/yd * (2.4 kg/m 3) used for bridge
decks. It was concluded that no
restrictions were necessary on the
use of the material based on its NaCl
content. Further, because the
recycled material is used only as the
aggregate portion, the overall level of
sodium chloride in the new concrete
is even less; namely, the amount of
NaCl in the recycled PCC times the
fraction of the new concrete that is
recycled material.
In preparation for a recycling project,
the State of Connecticut examined
the total chloride content of recycled
PCC material and found NaCl
contents of 12 Ib/yd 3 (7.1 kg/m 3) at
the 1.5 in (38 mm) level, 0.96 Ib/yd 3
(0.57 kg/m 3) at the 4 in (102 mm)
level, and 0.27 Ib/yd 3 (0.16 kg/m 3)
at the 6.5 in (165 mm) level. (6) The
new mixture with the recycled
concrete aggregate contained 1.93
Ib/yd ? (1.15 kg/m 3) total sodium
chloride.
These findings suggest that checking
the NaCl content of any recycled
material that may have excessive salt
and calculating the NaCl content for
the new mix are advisable. Based on
the results, any additional steps (such
as reinforcement coating) necessary
to avoid corrosion problems could be
taken.
Alkali-aggregate reactivity
Three conditions are necessary to
Cause damaging alkali-aggregate
reactivity: An aggregate with
sufficient amounts of reactive
constituents that are soluble in highly
alkaline solutions; enough water-
soluble alkali from some source
(usually the cement) to increase the
pH of the liquid in the concrete to
14-15 long enough to produce
swelling alkali-silica gel; and sufficient
water to maintain the solutions and
provide moisture for the swelling of
the gel.
The consequences of using recycled
PCC material that has suffered from
alkali-aggregate reaction as an aggre-
gate in a new concrete have not been
studied thoroughly. This special case
of PCC recycling requires answers to
several questions. How severe is the
reaction and the resulting distress at
the time of recycling? Has the
September 1985 « PUBLIC ROADS
reactive mineral matter been
completely used? If petrographic or
other examinations indicate this, it
may be safe to use the material. On
the other hand, using a low-alkali
cement in the new concrete may not
prevent further alkali-aggregate
reaction with the recycled material
because the reaction may continue
within the recycled material between
the old mortar and aggregate.
Probably the only safe way to screen
materials for this potential problem is
to perform long-term, mortar-bar
expansion tests (ASTM C-227) with
the recycled material in cements with
various alkali contents to determine
the acceptable level of alkali. If a
reaction occurs between the recycled
materials, there may be no level of
alkali in the cement low enough to
prevent the reaction. The addition of
limestone aggregate in the mix may
reduce the probability of alkali-
aggregate reactivity, but this is not
yet proven. (7) Reducing recycled
aggregate size also may be helpful in
controlling the reaction problem.
Recycling alkali-aggregate reactive
materials needs additional inves-
tigation, and work currently is
underway.
PUBLIC ROADS ® Vol. 49, No. 2
Field Projects With Recycled
PCC
Results from field projects where
recycled PCC was incorporated as
aggregate In the mixture should aid
the planning and conduct of future
recycling projects. In a 1976 recycling
project on U.S. Rte. 75 in lowa, the
entire crushed recycled PCC from a
secondary crusher (1.5 in [38 mm|
minus) was placed in a single stock-
pile. (2) Segregation problems
resulted as well as inconsistent feed
through the automatic bin gates of
the batching plant. To alleviate the
problem on subsequent projects, the
material was split on the 3/8 in (9.5
mm) sieve. Using recycled material
for both coarse and fine aggregate
produced a harsh, nearly unworkable
mix. Adding 15 percent concrete
sand made the mixture much easier
to work. Also, less air entraining
agent was needed to reach the
desired air content than for a conven-
tional mix. Because contaminants
often affect the air content of the
new concrete, their amount in the
recycled material must be controlled.
Approximately 75 to 80 percent of the
old pavement was recovered as
crusher product.
Using the experience gained in the
initial project, lowa conducted two
additional projects in 1977. As in the
first project, the crusher product was
low in fine material (22 to 24 percent
passing the No. 4 [4.75 mm] sieve).
A three-aggregate blend (coarse and
fine recycled, plus concrete sand)
controlled the segregation of the
recycled material and made a work-
able mixture. Washing the recycled
material was unnecessary if proper
removal and processing practices
were followed.
The 1980 recycling project using a
““D” cracked pavement on U.S. Rte.
59 in southeastern Minnesota found
that the crushed material passing the
No. 4 (4.75 mm) sieve is very angular
and increases water demand and
cement content when used in the
mix. (5) To avoid this situation, the
minus No. 4 (4.75 mm) material was
removed from the crushed concrete
and used as a stabilizer in the base
material. However, the material still
needed constant watering to achieve
target densities. A blend of 60
percent recycled coarse aggregate
and 40 percent natural sand was
expected to provide enough recycled
material for coarse aggregate in the
mix. The actual yield was very close
to this estimate.
Specifications
Several States have developed speci-
fications covering all phases of the
construction for removing, crushing,
storing, and incorporating recycled
materials into new PCC. (7, pp.
140-143) The following discussion of
specifications refers only to items
directly affecting the recycled aggre-
gate material.
Removal and contamination. Some
limit should be set on the amount of
allowable contamination from any
asphalt overlay, patch, joint sealant,
or subbase material in the material
recycled. Some amount of adhering
asphaltic concrete is allowable and
not detrimental to the mixture.
Crushing and stockpiling. The
maximum size of material should be
specified and may vary depending on
the use of the concrete. The top size
typically specified is 100 percent less
than 1 1/2 in (38 mm). The maximum
size specified may have to be reduced
(100 percent less than 3/4 in [19
mm]) if the material being recycled is
a ''‘D” cracked pavement. Standard,
good stockpiling techniques should
be followed, and the plus 3/8 in (9.5
mm) and minus 3/8 in (9.5 mm)
material should be stored separately
to avoid segregation. Usually,
washing is not necessary; however,
individual job conditions should
dictate this. The amount of minus
No. 200 (0.075 mm) material should
be limited to a maximum percentage.
41
Mix proportions. Crushed, recycled
material may be used for both the
coarse and fine aggregate; however,
specifying 15 to 30 percent natural
sand in the fines will improve the
workability and the finishability of the
mix. Trial mixes made in the labora-
tory should determine mix propor-
tions. The proportion of coarse to
fine recycled material used in the
concrete should be the same as the
crusher produces, if possible.
The cement factor will be determined
according to the strength desired, as
with a conventional mix. The water
content should provide acceptable
workability and finishability without
requiring excessive cement to
maintain strength. As mentioned
above, natural fine aggregate may be
added to improve these characteris-
tics while holding the water content
at a reasonable level. Water-reducing
admixtures also may be specified to
maintain the water/cement ratio at an
acceptable level. Air entrainment also
will increase workability.
Durability. The durability of the
concrete produced should be checked
in the laboratory according to ASTM
C-666 or some equivalent method. !f
recycled alkali-aggregate reactive
material is used, the expansive char-
acteristics of the new concrete also
may be checked with ASTM C-227
or an equivalent method to determine
if it will perform adequately.
Air entrainment. Air content may be
specified and obtained by adding an
approved air entraining agent, as with
a conventional mix. If the recycled
material is air entrained, the specified
air for the new concrete may have to
be set higher than usual because the
measured air will include the newly
entrained air plus the air content of
the recycled material. When the air
content of the recycled material is
subtracted from the measurement
obtained on the new plastic concrete,
the residual then will provide a
measure of the amount of air in the
new mortar. The presence of organic
contaminants may cause high air
contents; therefore, de-air entraining
agents may be needed.
42
Conclusions
In many instances, the recycling of
PCC as aggregate in a new concrete
is a viable alternative to the use of
natural aggregate. Research has
shown that with proper planning,
testing, and construction techniques,
high-quality concrete can be made
using recycled PCC as aggregate.
Further work needs to be done on
the use of recycled concrete that has
undergone ‘‘D” cracking or alkalli-
aggregate reaction; the long-term
behavior of this material when used
as aggregate still is not known.
Critical chloride contents for recycled
concrete in various applications also
are not yet well established.
Current knowledge and practices in
the recycling of PCC pavement will
be summarized in a National Coop-
erative Highway Research Program
synthesis study. Recycling of PCC
also will be one of the subjects
addressed by the Strategic Highway
Research Program.
REFERENCES
(7) LaHue, Darter, et al., ‘‘Proceedings of
the National Seminar on PCC Pavement
Recycling and Rehabilitation,’’ Report No.
FHWA-TS-82-208, Federal Highway
Administration, Washington, DC,
December 1981.
(2) J.V. Bergren and R.A. Britson, ‘‘Port-
land Cement Concrete Utilizing Recycled
Pavement,’ Report No. FHWA-DP-47-1,
Federal Highway Administration, Wash-
ington, DC, January 1977.
(3) ‘‘Pavement Recycling: Summary of
Two Conferences,’’ Report No.
FHWA-TS-82-224, Federal Highway
Administration, Washington, DC, April
1982.
(4) A.D. Buck, ‘‘Recycled Concrete, Util-
ization of Waste Materials and Upgrading
of Low-Quality Aggregates,’’ Highway
Research Record 430, 1973.
(5) A.D. Halverson, ‘‘Recycling Portland
Cement Concrete Pavements,’’ Report
No. FHWA-DP-47-3, Federal Highway
Administration, Washington, DC, May
1981.
(6) K.R. Lane, ‘Construction of a
Recycled Portland Cement Pavement,”’
Report No. 646-1-80-12, Connecticut
Department of Transportation, September
1980.
(7) W.J. Heck, ‘Study of Alkali-Silica
Reactivity Tests to Improve Correlation
and Predictability for Aggregates,’”’
Cement, Concrete, and Aggregates, vol.
5, No. 1, Summer 1983, pp. 47-53.
Stephen W. Forster is a geologist in
the Pavements Division, Office of
Engineering and Highway Operations
Research and Development, FHWA.
He is task manager for Task 1W1,
“’Pavement-Tire Frictional Interac-
tions,”’ in the Federally Coordinated
Program of Highway Research,
Development, and Technology. Since
joining FHWA in 1975, Dr. Forster
has worked in the areas of rapid
testing of aggregate gradation, skid
resistant aggregate and pavements,
more durable aggregate for pave-
ments, and repair of asphalt and port-
land cement concrete pavements.
September 1985 ¢ PUBLIC ROADS
Research Needs in Asphalt Technology
by
E.T. Harrigan
Introduction
This article discusses from the perspective of the Federal
Highway Administration (FHWA), research needs in
asphalt technology — one of six topics selected by the
American Association of State Highway and Transporta-
tion Officials (AASHTO) to receive special attention in the
planned Strategic Highway Research Program (SHRP).
FHWA supports this selection and, along with other inter-
ested public and private organizations, will provide
specific recommendations on needs and methods in 1985
and beyond as AASHTO formally develops a scope and
plan for each study area.
In 1983, before the SHRP was conceived, FHWA
reviewed asphalt research needs as a preliminary step in
developing an asphalt research program. Expert opinions
were gathered on the desirability and practicality of
changing current asphalt specifications, particularly by
including measures of asphalt chemical composition, to
improve asphalt pavement performance. Including asphalt
PUBLIC ROADS ® Vol. 49, No. 2
chemistry in asphalt specifications has generated great
interest in recent years as a possible solution to premature
or catastrophic asphalt pavement failure. Indeed, there is
a misconception that the main thrust of the SHRP asphalt
technology program will be asphalt chemistry. However,
AASHTO states that the following five needs will be
equally important (7) ?':
e Define properties of different asphalts.
e Improve testing and measuring systems.
e Determine relationships between asphalt cement and
pavement performance.
e Develop improved asphalt binders.
e Validate performance in the field.
The importance of asphalt chemistry in influencing pave-
ment performance, particularly pavement distress, must
be evaluated to develop a sound research program. A
brief historical review of asphalt chemistry research may
help explain the present situation.
1 Italic numbers in parentheses identify references on page 45
Developments in Asphalt Chemistry
Research
FHWA and its predecessor, the Bureau of Public Roads,
had a strong, productive program of asphalt research
from the 1930’s into the early 1970's. This program, which
stressed the study of asphalt rheology and the develop-
ment of tests and specifications, was instrumental in
introducing the asphalt grading systems and standard test
methods used today throughout the United States.
FHWA also stressed the basic chemistry of asphalts,
particularly how the chemical constituents of asphalt
interact with aggregate, moisture, and oxygen, and how
chemistry influences the aging of asphalt in a pavement. (2)
Reports of premature distress in asphalt pavements
increased sharply in the past decade. A perception devel-
oped that pavement failures evidenced by rutting,
stripping, and cracking were occurring at an unprece-
dented rate and that materials and designs that had
always given Satisfactory performance now were yielding
pavements that failed unpredictably and prematurely.
Combined with the 1973 oil embargo that disrupted tradi-
tional crude oil sources for U.S. asphalt production and
the introduction of new refining technology on a massive
scale, a consensus developed in the highway community
that a primary cause of asphalt pavement distress and
failure was a subtle, but significant, change in the quality
of U.S. asphalt cements. Several studies sponsored by
private organizations and by FHWA failed to detect major
differences in physical properties between pre- and post-
1973 asphalt cements. In fact, the data indicate that the
physical properties of the asphalt cements in a given
grade have changed very little in 35 years despite major
changes in crude oil sources and refining technology over
this same period.
Could two AC-20 asphalts, one produced in 1950 and the
other in 1980, have the same physical properties (for
example, viscosity and ductility) but still have chemical
compositions so different that their individual perform-
ances in pavements vary significantly? The answer is a
qualified “‘yes’’— although two materials with the same
chemical composition will have the same physical prop-
erties, the converse is not necessarily true. For example,’
the viscosities of chloroform and methanol are approxi-
mately the same at 20 °C (68 °F), and the densities of
water and asphalt are approximately the same at 25 °C
(77 °F); chemically, the members of each pair are very
different. However, although the chemical composition of
crude oils varies widely, limits of chemical composition
can be defined within which all crude oils fall. Conse-
quently, the chemical composition of asphalts will fall
within natural limits. Therefore, a change in crude oil
source should not radically alter asphalt physicochemical
properties. Changes in asphalt composition can contribute
to pavement performance problems, but these changes
Cannot account for all the poor performance noted in the
last decade.
44
The chemical composition of an asphalt is directly
involved in some important causes of pavement distress,
such as stripping. The size and structure of the compo-
nent molecules of asphalt are important in determining
the physical properties of the asphalt. Also important are
the associative forces between individual molecules and
those forces that provide bonding between the asphalt
and aggregate. These forces are highly dependent upon
the heteroatom content of the asphalt (primarily nitrogen,
oxygen, sulfur, and trace elements). Asphalt molecule
functional groups containing heteroatoms are directly
involved in the mechanism of stripping. (2)
Asphalt chemistry also is important in the aging of asphalt
in a pavement. Aging predominantly involves reaction of
oxygen with the asphalt, resulting in changes in molecular
size, structure, and functional group content, and is
reflected in changes in rheological properties. The
passage of time structures the asphalt in a manner
analogous to crystallization and without the need for
external agents such as oxygen or moisture. Structuring
on a molecular level is manifested as hardening of the
pavement.
This discussion of asphalt chemistry suggests that, while
important, it does not account entirely for premature and
pervasive asphalt pavement distress. Also, asphalt chem-
istry research in the SHRP should be narrowly defined
and goal oriented, confirming the view expressed by
AASHTO. (7) An extensive asphalt chemistry research
program is neither warranted nor possible with the
resources available.
Considerations for an Asphalt Research
Program
The expert panel convened by FHWA in 1983 made
several significant remarks about the state of asphalt tech-
nology. To develop a research program to address the
problems evident in asphalt pavement performance, the
following should be considered:
e Asphalt is rarely the sole culprit in a pavement failure.
Asphalt chemistry alone cannot account for the perform-
ance of pavements under traffic loading.
e Chemical specifications for asphalts would be unreal-
istic, but chemical factors can be used to evaluate the
overall quality of an asphalt.
e Asphalt specifications overemphasize handling qualities.
The gap between asphalt specifications and asphalt
mixture properties should be bridged with performance-
related specifications that address conditions such as
rutting, cracking, stripping, and adhesion.
e The dominant chemical factors that influence asphalt
performance and how these factors interact must be
determined and quantified.
September 1985 ¢ PUBLIC ROADS
e Moisture is the worst enemy of an asphalt pavement,
but many pavement failures can be traced to improper
mix design or construction techniques. An asphalt can be
too hard because asphalt films are too thin, air void
contents are too high, or the choice of asphalt grade is
poor.
e Materials and construction specifications are not
enforced; the fundamentals of proper mixture and pave-
ment design and construction are neglected.
¢ Highway agencies and contractors need a working
knowledge of the physicochemical properties of each
asphalt used, not just of the grade of the asphalt, so that
production and construction procedures can compensate
for any shortcomings and take advantage of the asphalt’s
strong points.
This strong emphasis on a balanced research program,
examining both asphalt mixture behavior and asphalt
physicochemical properties, combined with attention to
proper construction techniques and the intelligent use of
available materials can prevent many pavement failures.
When asked to recommend a list of topics that FHWA
might include in an asphalt research program, the panel
of asphalt technologists arrived at nine topics from a list
of 39 different items discussed. In order of importance,
the list includes the following:
1. Moisture damage mechanisms. Determine the adverse
effect of moisture on pavements, the physicochemical
interactions that produce these effects, and how these
effects are reflected in changes in asphalt and aggregate
properties. Explore the long-term results of moisture
damage on pavement performance and methods to
control the damage mechanisms.
2. Training and technology transfer. \dentify and imple-
ment training activities and multimedia technology sharing
to improve asphalt mix design, construction practices,
and inspection and quality control in all phases of asphalt
pavement construction.
3. /mproved asphalt specifications. Synthesize existing
information and field data to evaluate the possibility of
simplifying asphalt specifications, particularly eliminating
the asphalt residue and penetration grading systems.
4. Low-temperature behavior. Investigate how asphalt
responds to various cooling rates and how it accommo-
dates repeated strains in the cold weather service range.
In addition, develop a measure of low- temperature
stiffness in fundamental units.
5. Asphalt additives to upgrade desirable asphalt charac-
teristics. Investigate additives to upgrade or control
asphalt properties (such as oxidative and steric hardening
and temperature and shear susceptibilities) and to coun-
teract pavement distress mechanisms that lead to rutting,
cracking, and stripping.
6. External effects on asphalt performance in service.
Investigate on a controlled basis by locality and climate
how asphalt specification grade, mix design, and
construction practices determine or influence pavement
performance.
PUBLIC ROADS ® Vol. 49, No. 2
7. Establish relationships between asphalt rheology and
mixture rheology. |Investigate techniques to measure the
influence of asphalt rheology on mixture rheology,
emphasizing the mixture stiffness at low temperature; the
correlation of asphalt flow properties with field perform-
ance; the development of mix design methods to
compensate for variations in asphalt rheology; and the
measurement of properties such as viscosity, ductility,
and direct tensile strength over the whole asphalt service
temperature range.
8. Asphalt chemical functionality. Characterize the
chemical functionality of asphalt, emphasizing the
chemical groups that interact with moisture, oxygen, and
aggregate and that influence the rheology of an asphalt
over its service life.
9. Effects of new production equipment and techniques.
Investigate how hot-mix production methods that allow
moisture retention in aggregates and mineral fines in
asphalt influence asphalt and aggregate mixture quality.
Explore the need to change mix design methods to
compensate for various mix production technologies.
A series of studies would be needed to accomplish the
goals of each of these nine topics, but the total program
would not be as large as that envisioned for asphalt tech-
nology in the SHRP. In its final form, the SHRP probably
will encompass a much wider spectrum of research areas.
The SHRP has the resources to provide a unique opportu-
nity toward solving several important problems. FHWA
welcomes the opportunity to participate in the develop-
ment and conduct of research in asphalt technology as
well as in the other five topic areas.
REFERENCES
(7) ‘“America’s Highways, Accelerating the Search for Innova-
tion,’ Special Report No. 202, Transportation Research Board,
Washington, DC, January 1984.
(2) J. Claine Petersen, ‘‘Chemical Composition of Asphalt as
Related to Asphalt Durability — State of the Art,’’ Report No.
FHWA/RD-84/047, Federal Highway Administration, Wash-
ington, DC, July 1984.
E.T. Harrigan is a research chemist in the Materials Divi-
sion, Office of Engineering and Highway Operations
Research and Development. Before joining FHWA in
1974, he was a weapons test project officer for the Air
Force Systems Command. Dr. Harrigan currently is
project manager for contract studies in several areas of
materials research, including delineation, alternative binder
materials, deicing chemicals, asphalt, and methanol fuel
production.
45
SLOW
HILL
BLOCKS
VIEW
Limited Sight
Distance Warning for
Vertical Curves '
by
Mark Freedman, L.K. Staplin,
and Lawrence E. Decina
This article summarizes the
methodology and findings of a
Federal Highway Administration
(FHWA) contract study to
evaluate highway signs designed
to warn motorists of restricted
sight distance because of crest
vertical curves. Driver awareness,
understanding, and response to a
new warning sign (see display art)
that was developed were better
than for the existing LIMITED
‘This article summarizes ‘‘Limited Sight
Distance Warning for Vertical Curves,’’ Report
No. FHWA/RD-85/046, Federal Highway
Administration, Washington, DC, November
1984. The report is available from the National
Technical Information Service, 5285 Port Royal
Rd., Springfield, VA 22161 (Stock No. PB 85
193399).
46
SIGHT DISTANCE warning sign.
However, the new sign’s effec-
tiveness still was minimal. As a
result of this evaluation and of a
previous study conducted by the
New York State Department of
Transportation (7) ?, the National
Committee on Uniform Traffic
Control Devices voted to elimi-
nate the LIMITED SIGHT
DISTANCE sign (W14-4) from the
Manual on Uniform Traffic
Control Devices (MUTCD). FHWA
plans to issue a Final Rule to
delete this sign from the MUTCD.
Italic numbers in parentheses identify refer-
ences on page 53.
Introduction
Contemporary roadway geometry and
highway design features must satisfy
safety and operational requirements
of the vehicle and the driver. Promi-
nent among these highway design
features are vertical and horizontal
alignment, superelevation, delin-
eation, guardrails, signals, signs, and
lighting. One of the most important
aspects of highway design is to
provide sufficient sight distance to
enable the driver to respond properly
to situations ahead. Modern
highways, therefore, are designed
and built with horizontal and vertical
Curvature appropriate for the planned
speed and composition of traffic.
Many older highways, however,
evolved from old pathways used by
slow vehicles, and the highway
design is not appropriate for modern
traffic. Gradual improvements to the
roadway, especially upgraded paving,
allowed traffic to operate more
smoothly at higher speeds. However,
On many two-lane rural roads, hori-
zontal and vertical alignments were
not upgraded to match the level of
service offered by the roadway
surface.
September 1985 © PUBLIC ROADS
On two-lane roads with poorly
designed crest vertical curves, drivers
cannot see far enough beyond the
crest of the hill to determine whether
a hazard, such as debris on the
roadway, pedestrians, bicyclists,
animals, or another vehicle, exists
ahead. An intersection just beyond a
hill crest, where neither the main-
stream nor the crossing traffic can
see each other's approach, is
especially hazardous. Passing
maneuvers at crest vertical curves are
equally hazardous; motorists do not
have sufficient time to avoid
oncoming Cars.
Such situations occur most often on
low volume two-lane rural highways
that once carried primarily local
traffic. Local drivers who know of the
danger at these vertical curves with
restricted sight distance reduce their
speed or are more attentive while
approaching the curve. Unfamiliar
drivers, however, who may represent
a large portion of traffic on highways
in recreational areas, are unaware of
the danger and generally do not
exercise such cautious behavior.
One solution to the crest vertical
curve sight distance problem is to
reconstruct the vertical curvature;
however, this is very expensive and
may not be cost-effective in most
cases. Another solution is to limit
traffic speed to ensure sufficient
response time to hazards. However,
the safety of frequent and abrupt
speed-limit reductions on high-speed
highways is questionable. A more
cost-effective and rational approach is
to warn the motorist of the potential
hazard and to advise of a safe speed
through the hazard area.
This warning approach was adopted
with the incorporation of the
LIMITED SIGHT DISTANCE verbal
sign (W14-4), supplemented with a
speed advisory panel, into the
PUBLIC ROADS ® Vol. 49, No. 2
Manual on Uniform Traffic Contro/
Devices in 1976. However, the effec-
tiveness of this sign, either with or
without a speed advisory panel, has
been questioned. Although familiar to
traffic engineers, the terminology of
the sign legend is not familiar to
motorists, so it was not known
whether motorists adequately
comprehend the sign to reduce speed
and increase attentiveness.
In 1982, a Federal Highway Adminis-
tration contract study was conducted
to develop and test an improved
limited sight distance warning sign for
crest vertical curves. Study objectives
included the following:
e Test the effectiveness of developed
alternative warning signs as well as
the LIMITED SIGHT DISTANCE sign
with and without a speed advisory
panel.
¢ Compare the effectiveness of
vertical curve warning signs with
other traffic control devices.
e Provide recommendations for
proper use of the selected warning
sign.
Work on these objectives was
preceded by a literature review to
determine performance objectives for
vertical Curve warning signs.
Highway Sign Performance
Objectives
Although the literature on highway
signs contains extensive information
on legibility, noticeability, compre-
hension, and other sign/driver
performance measures, little has been
written about the performance of the
LIMITED SIGHT DISTANCE sign in
particular.
The effectiveness of the LIMITED
SIGHT DISTANCE sign has not been
proven. A study of vehicle speed,
driver comprehension, and accidents
at LIMITED SIGHT DISTANCE sign
sites in New York showed that either
the sign had no impact on drivers’
speeds or that drivers reduced their
speeds only after the sign was
removed. Only about one out of
every six motorists fully understood
the sign’s meaning, while half recog-
nized the advisory speed but did not
know that the warning referred to the
hill. The sign’s effect on accident
reduction could not be concluded. (7)
Also in New York it was found that
the LIMITED SIGHT DISTANCE sign
is used where resurfacing and/or
other minor road improvements result
in at least a 5-mph (8-km/h) increase
in speed above the design value for
the vertical alignment. (7)
The LIMITED SIGHT DISTANCE sign
has become the second most
frequently used sign (horizontal curve
warning is first) at all recent highway
rehabilitation projects where signing
has been installed. The availability of
the LIMITED SIGHT DISTANCE sign
has allowed many substandard
vertical curves to be treated with
resurfacing and sign installation rather
than reconstructing the vertical
curvature, which is not always cost-
effective.
The parameters that determine sight
distance on crest vertical curves are
the change of gradient (A), the
length of the curve (L), the driver's
eye height (he), and the height of the
obstacle to be seen (h,). The
following equation is used to deter-
mine the length of the curve required
to provide a given sight distance (S):
AS ?
100 (Vv 2he+V 2h,) 2
Thus, the sight distance provided by
a particular geometric layout is:
S=10V L/A (V 2he+V 2h.)
Setting sight distance on vertical
curves is determined by the distance
required to stop for an obstacle on
the road:
D=1-467(RT)V-+V7/00Uf = s)
Where,
D = Stopping distance (ft).
RT = Reaction time (s). (The
American Association of State
Highway and Transportation Officials
currently uses 2.5 s).
V = Speed (mph).
f = Tire-pavement coefficient of
friction. (The range for wet pavement
is 0.36 at 30 mph [48 km/h] to 0.29
at 70 mph [113 km/h]).
s = Longitudinal slope of roadway.
47
The stopping distance for vertical
curves is extremely sensitive to
speed, friction, and reaction time. For
speeds near 55 mph (89 km/h), for
each 1 mph (1.6 km/h) that speed is
reduced, stopping distance is reduced
by about 9 ft (2.7 m) on dry pave-
ments and by about 14 ft (4.3 m) on
wet pavements. Similarly, stopping
distance is reduced by about 8 ft (2.4
m) for every 1/10 s reduction in
reaction time. Therefore, a warning
device that causes a driver to reduce
his/her speed and be more alert also
reduces the time needed for detec-
tion, recognition, and control
movement, and thus substantially
reduces stopping distance. A warning
device that reliably reduces traffic
speed and minimizes reaction time by
heightening driver attentiveness to
the potential problem ahead would be
a highly cost-effective treatment for
the typical vertical curve with
restricted sight distance.
Other research (2-5) on warning signs
has shown that signs augmented by
constantly flashing lights or vehicle-
actuated flashers are more effective
in reducing speeds than signs without
flashers. Generally, flashing lights
should be used only where a real
hazard is likely to be present or is
especially severe. Flashing lights are
most effective in reducing drivers’
speeds and increasing their attention
when a hazard is obvious, such as a
wet roadway or sharp horizontal
curve, and therefore may not be
appropriate for most vertical curves
with restricted sight distance.
48
Development of Alternative
Sign Candidates
The literature review pointed to the
need for an understandable and
effective alternative to the LIMITED
SIGHT DISTANCE sign. In devel-
oping and evaluating alternative
warning signs, numerous verbal and
symbol candidate signs were
prepared, and laboratory experiments
were conducted to eliminate the least
promising candidates and select the
most promising candidates for field
testing.
Preparation of sign candidates
Thirteen preliminary verbal messages
were created using various combi-
nations of key words selected to
convey a preparatory element (the
appropriate degree of attentiveness),
an action element (what the motorist
must or must not do), and an identifi-
cation element (defining the hazard).
In addition, 10 candidate symbols
were prepared to depict the vertical
curve sight distance situation from
front, side, and perspective views as
well as several more abstract repre-
sentations. Each verbal and symbol
candidate was prepared as a small,
individual cardboard sign.
A sample of 41 respondents
examined each of the verbal and
symbol candidates and ranked them
according to how well each candidate
conveyed caution because of a hill
crest restricting vision of possible
traffic hazards.
The most highly ranked verbal
candidate messages were CAUTION
HILL BLOCKS VIEW, DANGER HILL
BLOCKS VIEW, and SLOW HILL
BLOCKS VIEW. The candidate
message DANGER HILL BLOCKS
VIEW was eliminated because
DANGER was believed to be too
strong for most situations where no
danger is apparent, and overuse of
the word might diminish its value.
The two most highly ranked symbols
were both side views depicting one or
two vehicles approaching the hill
crest. A third candidate showing a
single car, an obstruction, and an
occluded line of sight also was
recommended by FHWA for further
testing.
|
The signs recommended for further |
laboratory testing are shown in figure 1.
Laboratory experiment
The laboratory experiment was
conducted to determine how well and
how quickly the LIMITED SIGHT
DISTANCE sign and each of the
other candidate warning signs were
understood and assimilated by motor-
ists. A total of 256 drivers, from 16 to
75 years old and equally comprised of
men and women, were test subjects.
Testing was performed in an urban
and rural area in two State-operated
motor vehicle inspection centers in
New Jersey and two drivers license
photograph centers in Pennsylvania.
The laboratory experiment consisted
of three complementary tests—a
comprehension test, an assimilation
test (speed of recognition), and a
ranking test—for each of the candi-
date signs shown in figure 1. The
LIMITED SIGHT DISTANCE sign was
tested with and without a 35 mph (56
km/h) advisory speed panel. The
CAUTION HILL BLOCKS VIEW sign
was tested with and without a.
supplementary panel with the legend
INTERSECTION. Each subject was
exposed to only one of the candidate
signs and three similarly shaped, but
otherwise unrelated, distractor signs
to eliminate any learning effect from
alternative candidates. Slides of the
signs set in an identical, real-world
background of a hilly, two-lane rural
road were displayed on a screen to
each subject.
For the comprehension test, slides of
the selected candidate sign and its
three distractor signs were projected,
and each subject was asked to
explain what the message or symbol
meant and what the subject would do
if he/she encountered the sign while
driving. No time limit was imposed on
this part of the experiment.
In the assimilation test, each subject
examined and became familiar with
one selected candidate sign and set
of distractors, then identified each
sign when exposed to a very brief
(50 ms) projection.
September 1985 © PUBLIC ROADS
For the ranking test, each subject
was given a packet of three miniature
verbal signs and asked to rank which
sign was the best, next best, and
worst at conveying the intended
warning. The same procedure was
used to rank the symbol signs.
Following are the principal findings of
the laboratory experiment:
e Of the verbal messages, SLOW
HILL BLOCKS VIEW scored highest
in comprehensibility and recogniza-
bility and was ranked second best
among verbal signs. This sign was
selected for further field testing.
e Of the symbol messages, the sign
depicting two vehicles approaching
each other from opposite sides of a
hill scored highest in comprehensi-
bility and second highest in recog-
nizability. It was overwhelmingly
preferred among symbols in the
ranking test. This sign also was
selected for further field testing.
e The currently used LIMITED SIGHT
DISTANCE verbal message was least
comprehensible of the verbal signs,
was least recognizable of all verbal
and symbol signs, and was deemed
worst by more test subjects than any
other symbol or verbal sign. This sign
was used as the basis for comparison
in the field tests.
e In the assimilation test, symbol
signs were correctly identified 50
percent more often than signs with
verbal legends.
LIMITED
SIGHT
DISTANCE
CAUTION
mab
BLOCKS
VIEW
SLOW
fd
BLOCKS
VIEW
Figure 1.— Candidate limited sight distance warning signs.
PUBLIC ROADS ® Vol. 49, No. 2
49
Field Tests of Candidate
Signs
The candidate verbal sign SLOW
HILL BLOCKS VIEW and the candi-
date symbol sign depicting two
vehicles approaching each other from
opposite sides of a hill (see display
art) were field tested under fully
operational conditions in a controlled
field test and an observational field
test. In the controlled field test,
subjects accompanied by a test
administrator drove a test vehicle
along a 12.6-mile (20.3-km) route
containing four vertical curves with
restricted sight distance that were
identified by a candidate warning
sign. Drivers’ abilities to notice and
remember the signs, correctly inter-
pret the signs, and respond appro-
priately were measured. In the obser-
vational field test, traffic sensing
equipment was placed on a roadway
at three vertical curves with restricted
sight distance to measure the speed
of passing motorists who were not
aware that a study was being
conducted.
The LIMITED SIGHT DISTANCE sign
was studied both with and without a
30 mph (48 km/h) advisory speed
panel at each of the study locations.
In addition, at one site located near
an intersection, a 12-in x 24-in (305-
mm x 610-mm) panel bearing the
legend INTERSECTION was placed
on the sign post below the LIMITED
SIGHT DISTANCE sign. At each site,
the symbol sign also was accom-
panied by a 24-in x 18-in (610-mm x
457-mm) verbal panel bearing the
legend SLOW HILL BLOCKS VIEW.
50
Controlled field test
Sixty-four drivers (28 men and 36
women) ranging in age from 18 to 69
years participated as test subjects.
The three dependent measures in this
study were observations of how
drivers responded to candidate signs
along the route, memory measures to
reveal which signs were most often
noticed and most correctly identified,
and expressions of relative preference
for each candidate limited sight
distance warning sign.
Driver responses to the signs were
measured as follows: As subjects
drove the route and encountered
each candidate warning sign, the
administrator recorded what the
driver did in response to the sign,
using a checklist that included
slowing or braking, any unusual or
inappropriate response, any remarks
concerning the sign, turning his/her
head toward the sign, or other
obvious responses.
Two different memory measures
assessed how well each subject could
remember the candidate signs distrib-
uted along the test route. In a free
recall test, drivers named from
memory as many signs seen along
the route as possible. They also were
asked to explain the meaning of each
sign that they recalled. In a recog-
nition memory test, drivers were
asked to indicate whether or not they
had encountered the signs shown in
a series of photographs.
Both the SLOW HILL BLOCKS VIEW
candidate sign and the symbol candi-
date sign were more frequently
recalled than either the LIMITED
SIGHT DISTANCE sign alone or with
the 30 mph (48 km/h) speed advisory
panel. SLOW HILL BLOCKS VIEW
was correctly interpreted more often
than any other sign.
Although the symbol candidate was
the second most frequently recalled
sign after SLOW HILL BLOCKS
VIEW, it was incorrectly interpreted
twice as often as it was correctly
interpreted. This misinterpretation
probably was because of the test
subjects’ lack of familiarity with the
new symbol.
In the recognition memory test,
SLOW HILL BLOCKS VIEW was
correctly recognized more often than
the other signs.
Both the SLOW HILL BLOCKS VIEW
and the symbol sign were greatly
preferred to the LIMITED SIGHT
DISTANCE signs in the preference
ranking test.
The study of behavioral responses
demonstrated that drivers responded
most often to the symbol sign,
primarily by slowing or braking.
The LIMITED SIGHT DISTANCE
sign, both with and without the 30
mph (48 km/h) advisory panel, was
associated with poorer performance
than either of the other candidate
signs in the recall test and the pref-
erence ranking test.
Results of the controlled field test are
shown in tables 1-4.
September 1985 ¢« PUBLIC ROADS
LED ES EE OR ET PE SE EEE LE EEE ETE ET
Table 1.—Recall memory performance tor target
stimuli in controlled field test
Incorrect
Candidate Total number ot Correct
warning sign times remembered — interpretations Interpretations
Symbol sign 21 7 14
SLOW HILI
BLOCKS VIEW 26 23 3
LIMITED SIGHT
DISTANCE 18 13 5
EIMIC EDs Gra
DISTANCE—30 mph
advisory panel 4 3 |
I mph=1.6km/h
Table 2.—Recognition memory performance for target
stimuli in controlled field test
Number of ‘‘yes”’
Candidate warning sign responses Percent correct
Symbol sign 36 45
SLOW HILL BLOCKS VIEW 43 67
LIMITED SIGHT DISTANCE 37 58
LIMITED SIGHT DISTANCE—
30 mph advisory panel 29 45
I mph=1.6km/h
Table 3.—Preference ranking of candidate warning signs in
controlled field test—frequency counts and weighted scores
LIMITED SIGHT
DISTANCE—30 mph
advisory panel
LIMITED
SIGHT DISTANCE
Symbol SLOW HILL
sign BLOCKS VIEW
Position | 30 23 4 v
(best)
Position 2 13 24 10 17
Position 3 7 9 18 30
Position 4 14 8 32 10
(worst)
Weighted scores 187 190 114 149
I mph=1.6 km/h
ETE SS en a ee OS ES SET ON sn Ea a eo Ens ee
Table 4.—Driver behavior response to candidate
warning signs noted during controlled field test
LIMITED SIGHT
DISTANCE—30 mph
advisory panel
Symbol SLOW HILL
sign BLOCKS VIEW
LIMITED
SIGHT DISTANCE
Slowing or
braking 25 22 13 21
Inappropriate
response 0) 0 0 0
Makes remark 6 5 3 6
Overt orienting
response (eye
fixation of
over 2S) 5 pi 0 l
Other 0 ] 0) 0
Driver swerved across lane boundary while staring at sign.
I mph=1.6km/h
PUBLIC ROADS ® Vol. 49, No. 2
Observational field test
This test, conducted concurrently
with the controlled field test at three
rural vertical curve sites with
restricted sight distance, was
intended to determine the extent to
which each of the candidate warning
signs tested influenced the driving
behavior of motorists who were not
aware that an experiment was being
conducted. Vehicle velocity was
measured for 5,338 vehicles at five
locations within an area 1,250 ft (381
m) before each vertical curve to 200
ft (61 m) beyond the hill crest. In
addition, vehicle lateral position and
other indications of driver response to
the warning signs were recorded.
The average daily traffic volume (both
directions) at the sites ranged from
2,000 to 3,750 vehicles. Posted speed
limits were 55 mph (89 km/h), 45
mph (72 km/h), and 40 mph (64
km/h). No traffic control devices
51
warning of sight distance restrictions
because of vertical curves existed at
any of the three sites before the
experiment.
Data were collected at each site for
the following sign conditions:
* Baseline—no limited sight distance
warning sign.
* SLOW ILE’ BLOCKS VIEW:
* Symbol sign with SLOW HILL
BLOCKS VIEW panel.
¢ LIMITED SIGHT DISTANCE.
¢ LIMITED SIGHT DISTANCE with
30 mph (48 km/h) speed panel.
At one site, a vehicle was parked on
the shoulder of the road beyond the
crest of the hill, thus out of drivers’
sight until they were within about 200
ft (61 m) of the hill crest. The sudden
presence of what appeared to be a
potential hazard was intended to
force drivers to take some antici-
patory or corrective action such as
reducing speed or moving toward the
center of the roadway.
Figure 2 shows a typical layout of the
data collection equipment and sign
placement for the observational field
teSie
Measures of vehicular velocity were
not sensitive enough to identify any
effects caused by differences among
signs. In general, velocity and
velocity difference measures for each
sign condition were similar; thus
neither statistically nor operationally
significant differences were evident.
Although some marginally statistically
significant differences between the
behavioral measures (including
braking, drifting left or right, crossing
the centerline, and crossing onto the
shoulder) associated with each sign
were discovered, no consistent
pattern could be defined, thus no
sign emerged as the superior
candidate.
edge of roadway
800 ft
“TH i aa
edge of roadway
475 ft
Figure 2.— Conditions and experimental layout for the observational field test.
Be
BZ ometite
——_—
vehicle
1 £t=0.305 m
September 1985 © PUBLIC ROADS
Conclusions From the Field
Tests
The effect that each sign had on
driver behavior could not be
measured by techniques used in the
observational field test. In the
controlled field test, however, driver
behavior was measurably influenced
by each of the candidate warning
signs. That influence was measured
by differences in the number of
observations of certain driver
responses, each driver's ability to
freely recall, recognize, and compre-
hend each of the warning signs, and
each driver's relative preference for
each candidate limited sight distance
warning sign. Clearly, the existing
LIMITED SIGHT DISTANCE sign,
with or without a supplementary
advisory speed panel, did not
produce desirable driver responses as
frequently as the SLOW HILL
BLOCKS VIEW sign or the symbol
sign, nor was the LIMITED SIGHT
DISTANCE sign recalled, compre-
hended, recognized, or preferred as
often as the SLOW HILL BLOCKS
VIEW sign or the symbol sign. These
candidate signs are more likely to
increase driver awareness that a
hazard may exist downstream than is
the existing LIMITED SIGHT
DISTANCE sign.
However, although the SLOW HILL
BLOCKS VIEW verbal sign candidate
and the symbol sign candidate are
the most desirable choices to replace
the LIMITED SIGHT DISTANCE sign,
neither candidate sign was very effec-
tive in influencing test subjects in the
field test to reduce speed. Less than
half of the drivers slowed or braked
for any of the signs. Therefore, the
importance of this study is that it
provides additional evidence of the
need to eliminate the use of the
LIMITED SIGHT DISTANCE warning
sign.
PUBLIC ROADS ® Vol. 49, No. 2
REFERENCES
(7) M.R. Christian, J.J. Barnack, and
A.E. Karoly, ‘Evaluation of Limited Sight
Distance Warning Signs,” Traffic and
Safety Division, New York State Depart-
ment of Transportation, February 1981.
(2) F.R. Hanscomb, ‘‘Evaluation of
Signing to Warn of Wet Weather
Skidding Hazard,’’ Transportation
Research Record No. 600, 7ransportation
Research Board, Washington, DC, 1976.
(3) R.W. Lyles, ‘An Evaluation of Signs
for Sight-Restricted Rural Intersections,”
Report No. FHWA/RD-80/022, Federa/
Highway Administration, Washington,
DC, February 1980.
(4) R.W. Lyles, ‘‘Alternative Sign
Sequences for Work Zones on Rural
Highways,’’ Report No. FHWA/RD-
80/163, Federal Highway Administration,
Washington, DC, May 1981.
(5) C.V. Zeeger, ‘‘The Effectiveness of
School Signs With Flashing Beacons in
Reducing Vehicle Speeds,’’ Report No.
429, Division of Research, Kentucky
Bureau of Highways, July 1975.
Mark Freedman is a senior transpor-
tation engineer in the Transportation
Research Group at KETRON, Inc., in
Philadelphia, PA. He served as
principal investigator for the FHWA
study described in this article. Mr.
Freedman has been conducting
research in the areas of highway and
pedestrian signing, safety, and visi-
bility for 14 years. He completed
another FHWA study to determine
the extent to which traffic signals
may be dimmed at night. He is a
member of the Transportation
Research Board Committee on Visi-
bility and Secretary of the Committee
on Motorcycles and Mopeds.
L.K. Staplin is a senior human
factors psychologist in the Transpor-
tation Research Group at KETRON,
Inc. Dr. Staplin has served as co-
principal investigator on an FHWA
study of reduced night lighting on
freeways. For 3 years he was a
visiting faculty member at Lehigh
University in Bethlehem, PA, and has
worked as a consultant with the Air
Force Human Resources Laboratory
at Williams Air Force Base in
Chandler, AZ.
Lawrence E. Decina is a transpor-
tation analyst at KETRON, Inc.
During the past 10 years he has
participated in numerous highway
safety studies concerning highway
lighting, signing, and pavement
serviceability.
53
300' 30° 500' 30'
14TH ST
PARKING
GARAGE
150 VPH
2.8 % GRADE
ot
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PARKING - 10 CARS ?
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ADAMS ST.
Netsim for Microcomputers
Scott W. Sibley
Introduction
Netsim, a computer model that simulates microscopic
traffic flow on urban streets, is one of the most powerful
traffic engineering and research tools available today.
Netsim was developed in 1971 as UTCS-1 to evaluate the
Urban Traffic Control System, a computer-based signal
control system. Today, there are about 130 Netsim users
in the United States and abroad. Over the years, the
model has been enhanced to include fuel consumption
and vehicle emissions data and other features requested
by its users. The mainframe program was written in ANSI
Fortran 66 and is portable to most mainframe computers.
he
‘Italic numbers in parentheses identify references on page 59.
54
The use of Netsim has been limited to users who have
access to a mainframe computer. Often, the lack of
Opportunity or cost of using a large computer has made
the use of Netsim impractical. Because of the growing
number of microcomputers in use, a version of Netsim
that runs on a microcomputer would make the program
available to a larger number of users. | have developed
such a version under a research fellowship with the
Federal Highway Administration (FHWA), Office of
Implementation. The microcomputer program is based on
the current version of Netsim with actuated signal logic
and is written in Fortran 77 for use on IBM-PC compat-
ible microcomputers. This microcomputer version makes
the use of Netsim feasible for an extended range of
problems, including much smaller networks and situations
in which a number of alternatives are to be examined.
September 1985 ¢« PUBLIC ROADS
Background
Simulation, particularly useful when studying a complex
situation that cannot be analyzed directly, allows
experimentation with design alternatives without
committing the resources necessary to implement the
alternatives in the field. Simulation is quicker and more
flexible than field evaluation and avoids the risk of
creating hazardous or undesirable operating conditions.
The user has complete control over the experimental
conditions, which allows one aspect of a problem to be
modified without changing other aspects. (2) However,
because a simulation is a simplification of the real world,
it has its limits. The quality of the results depends on the
time and care used in collecting data and preparing
inputs.
Netsim simulates urban traffic operations by modeling the
movement of individual vehicles through a network of
streets and intersections. Each vehicle responds to local
conditions such as signal control and neighboring
vehicles. (3) Netsim was developed to evaluate, not
optimize, a range of relatively complex traffic control
strategies. The model is especially useful for predicting
fuel consumption and vehicle emissions; however, it does
not generate or select alternatives. Netsim simulates a
range of network configurations and traffic control
schemes and analyzes bus stop placement, bus routing,
turn restrictions, turning pockets, parking control, and the
placement of traffic detectors.
The Netsim model is stochastic —traffic modeling is based
on probabilities of random events, and outputs have
random variability. Vehicles do not move according to
origin-destination travel paths because their routes depend
on fixed turning probabilities at intersections; therefore,
vehicles are not diverted from routes or intersections that
become congested.
pigs It
Translated By
eae he
Freproce
Sroproley
Fed
Popute thule CNE TSIM. DAI sArSAanr
The Microcomputer Version
The microcomputer version of Netsim is essentially the
same as the mainframe computer version. The Netsim
User Guide (2) is applicable to this version, and most data
sets from the mainframe version can be used with the
microcomputer version with little or no modification.
The program has been modified to fit the limits and
Capabilities of a microcomputer. The file-handling features
have been removed, and the user is given direct control
over the input and output files (fig. 1). The mainframe
version allows the user to specify several time intervals
with different traffic characteristics in each; the micro-
computer version is limited to simulation of one time
interval.
The microcomputer version of Netsim has the same size
limitations as the mainframe version. The program can
handle a network up to 160 links and 99 nodes and a
maximum of 20 actuated traffic signals. Up to 30 bus
routes can be included. The program handles a maximum
of 1,600 vehicles in the network at one time. Most
situations can be handled within these flexible limits.
The computation time of the microcomputer version
depends on the size of the network and number of
vehicles. This becomes a major factor for very large
networks. The simulator may run 10 hours or more for a
15-minute simulation on the largest possible network. A
more typical 30-intersection network will take approxi-
mately 1 1/2 hours. The user only needs to be present
during the first 5 minutes of this time for the input
processing.
ew 17/35
Highway Administration
Version
Sy su
ise Cree
Stet ere dale cotati tote wt Nie SF se ee
Bee aa a WP
if Necessary
Ready Toa Write
Change Diskette
Weatinger ile AnNEL.FIL.
Ary
u
Ready Ta Run SIMUL
Figure 1. — Execution of preprocessor.
d Enter Drive SpecifierlAl:itcrs
» DONE
PUBLIC ROADS ® Vol. 49, No. 2
55
Performing the Simulation
The microcomputer version of Netsim is simple to use,
consisting of three separate programs that combine to
provide the complete Netsim package. To obtain useful
results, the user should have some knowledge of the
fundamentals of traffic engineering and an understanding
of the situation being modeled. Some user interaction is
required, but primarily the program runs itself using the
input files provided by the user.
The first step, which is the same for the mainframe
version, is to gather the required input information. The
user must collect the information for the network,
including the geometrics of the network; the signalization
and other traffic controls; traffic volumes, composition,
and turning percentages; bus routes, stops, and
schedules; and vehicle and driver operational charac-
teristics. Default values are built into the program or can
be assumed by the user where appropriate.
Next, the network must be reduced to a link-node
diagram (fig. 2). This could take several hours or several
days, depending on the size of the network, the avail-
ability of the information, the need for data collection,
and the experience of the user. The representation of the
network by a link-node diagram and the assumptions
made about the data to be used are critical in obtaining
useful and significant results. Much of the information
required is available for the study of the problem; little
additional data collection is needed.
Figure 2. —Link-node diagram.
56
The second step, as with the mainframe version, is to
prepare the input data set by using the Netsim coding
sheets and the Users Guide. (2) A card image file then
must be created using a text editor such as MS-DOS or
Wordstar. As for any program, the data set then should
be verified for accuracy, which could take from several
hours to several days, depending on the size and
complexity of the problem being modeled. A data set for
a single time interval from the mainframe can be used
without modification by transferring the file from the
mainframe to the microcomputer.
The third step is to run the preprocessor to check the
input data set for completeness and, to an extent,
consistency. A portion of the output from the preproc-
essor is shown in figure 3. The user then must correct the
data set and rerun the preprocessor. Even for a large data
set, each run takes less than 10 minutes.
The fourth step is to run the simulator, which performs
the simulation and accumulates the measures of effec-
tiveness. This step involves the major portion of computer
time, but the computer runs without assistance from the
user. The speed of the simulator depends on the options
selected and the reports requested, as well as on the size
of the network and the number of vehicles. A typical
simulation takes from 5 to 10 seconds of real time for
every second of simulation time. Sample run times are
shown in figure 4.
During the simulator run, the optional fuel consumption
and emissions program can be run for any additional
analyses that may be desired, such as using different
vehicle performance values. This program uses the vehicle
trajectory data generated by the simulator, so the analysis
is based on the same simulation. The user can alter the
vehicle fuel consumption and emissions tables to see the
effect of different vehicle characteristics on the network's
performance. Again, the speed of this program depends
on the number of vehicles in the network and the time
period simulated. However, the program runs quickly,
completing most problems in less than 1 hour.
September 1985 ¢ PUBLIC ROADS
A aE Se PS CSO IE TS OS SEE Ss ET EE
SIMULATION OF TRAFFIC
THE NETSIM MODEL
14TH ST PARKING GAR., NICETOWN » PENNSYLVANIA 0 01/30/85
POCK MEAN TURNING MOVEMENTS DESTINATION NODES PED LANE CHAN
LINK LANE SPAN LR U-F H LEFT THRU RT DIAG LEFT THRU RT DIAG LOST DEN 12345 TYPEG tL IDENTIFICATION
(QOL, 1) 2 900 9 0 ENTRY 22 0100 9 0) Ge Be it 0 GAD: a Fe 1
Cet espe re 300100. 30) 622 20 70 10 0 2 64 Wp Pay UU TUATO TH Sh 2 14TH ST EB
paesorerg ee wieS Sel ieeeeshav22 4S Oe 0) ae te NR A UAT ROY: 3 14TH ST EB
(GF 8) QUST 90n he 22 0100 0 0 ) 808 9 Oe? Gye Omens Oe On 0m Ome lame 4 14TH ST EB
(808, 8) 2 S500 06 0 ENTRY 22 0100 9 0) cum 0 0 OOO) the: n)
TRAFFIC SIGNAL DATA
* INDICATES RTOR IN EFFECT FOR THIS APPROACH
NODE INTVL DURATION OFFSET SIGNAL CODES FACING INDICATED APPROACHES
ee eS Eee cee) * ere cast tha AURA
a { 18 ( 30P) Ome Es) 2 2 ! 1
3 2 a By Sines OR) 2 ) )
3 3 OMe 7) 21 ~( S5P) 4 4 2 2
3 4 Samet) Oyo ae), 0 0 2 2
4 5 Deo ur) eh BAR) 9 9 2 2
3 6 % Cale) ay) SP) 0 0 z 2
Figure 3.— Sample of input summary report from preprocessor.
te a as te PST < ee eet Cacia =. * |
Nodes Avq.# = seashell Without With With O=-D |
Vehs. FC&E FC&E Tables
= 2% UO GLO] 8:40 A AD | |
vay 10:60 LES OKO) 123 46 14:40 14:30
50 7230 S300 10:00 tis 2o
as 6:00 15:00 Sea ON) PO Se Shr Hg)
igre. 6:90 aie Ka} 43:10
MADISON,WI 59 Ha CA FOROS) OLS) 14:00 eae]
es, 7200 |15:00 25:40 i
| Poe 8:45 decree G) Soe oe)
159 @:45 | 15:00 54210 |
| | |
WASHINGTON, DC teal 40 131 ae src) iba aa @)
TN a Se) sey 2a: 40 PI {IA9)
paral Se) aie 4:00 Si aiie Ee) 26:40
{ ee pee oe ee ee — 1 ______— a — =
Notes:
All times are given in minutes: seconds
Fill = Feriod before network reaches a state of equilibrium
Simul = Period when simulation 15 performed to gather statistical data
FC2E = Fuel Consumptian and Emissions
O-D = Origin-Destination
Figure 4.— Sample run times for typical networks.
PUBLIC ROADS ® Vol. 49, No. 2 57
As the fifth and final step, the user must analyze the
output to determine if additional simulations are required.
The user can examine the output with a text editor or
print it as a permanent record. Several measures of
effectiveness, such as average delay and cycle failure, are
provided to indicate how the network operated (fig. 5).
Based on this information, the user can make appropriate
changes to the network and compare the results. This
step could take several hours to several days, depending
on the level of detail required.
Advantages of the Microcomputer Version
The microcomputer version of Netsim can be used for
problems that would be too expensive or too time
consuming on a mainframe computer, making the |
program ideal for analyzing several alternative solutions to
a problem. Apart from the cost of the time required to
gather data and prepare the input data set, there is
virtually no cost for using the microcomputer version.
LINK STATISTICS AT TIME 8 21 0
VEK TURN MOVEMENT QUEUE LENGTH BY LANE
LINK OCC. OIS LEFT THRU RT. ee oe Eve it
(BOL, 1) 0 5 0 64 9 Om0e 0 0
ee Ag 1 46 tijd ieee as ee)
esce 1o1 LP Webbe Siege cine]? HES ASSESS
DELAY/ STOP CYC CURRENT AV. NO. SI6
VEH, DLY(P) FLR EVNT CHANNELIZATION SPEED STOP CODE
ma) CO er G aa ay 1) eB:
20.3 Ee gl aun 0 Oa aU 7.4 30 2
See AUP a MR oee Wallin Tl ia Mie gi) iy oe
CUMULATIVE STATISTICS SINCE BEGINNING OF SIMULATION
PRESENT TIME 1S 8 30 0, ELAPSED SIMULATED TIME IS 15 MINUTES, 0 SECONDS
LINK STATISTICS
VEH- VEH MOV, DELAY TOTAL T-TIME T-TIME/ D-TINE D-TIME/ PCT AVG. AVG. STOPS AVG CYCL
LINK MILES TRP TIME TIME M/T TIME / YEH. VEH-MILE / YEH VEH-MILE STOP SPEED OCC. /VEH SAT FAIL
V-MIN Y-MIN V-MIN = =SEC SEC/MILE SEC SEC/MILE DELAY PH PCT
Sul rs moe ood eg oY SOM cee eco Oded meer aed 309.9 Tet Oe ad ela. )
Pe TL Ey ET REP alee a aoRe PA Bley : 239.9 Let Oy Camm det 70 10 4
(PO Ore sO Oc in ee omen Of mec Omer eG 4.1 47.2 Je at g ~OGe) oe
NETWORK STATISTICS
VEHICLE-MILES= 91.86 VEHICLE-MINUTES= 36
Bt
MOVING/TOTAL TRIP TIME= .361 AVG. SPEED (MFH)= 9.75
ae
TOTAL DELAY= 361.1 MIN, DELAY /VEH-MILE=
VERICCESTRIPS NESTS = 9 357 STOPS/VEHICLE= 1.35
MEAN OCCUPANCY= 37.4 VEH. AVG DELAY/VEHICLE= 40.80 SEC
3 MIN/V-MILE TRAVEL TIME/VEH-MILE= 6.15 MIN/V-MILE
STOPPED DELAY AS A PERCENTAGE OF TOTAL DELAY=70.7
Figure 5.— Sample of output reports from simulator.
58
September 1985 ¢ PUBLIC ROADS
With the microcomputer version of Netsim, the program
can be run whenever a microcomputer is available; there
is no need to wait for access to a mainframe computer.
This can mean substantial savings over renting time on a
mainframe computer and makes it feasible to use Netsim
with smaller simulation problems and with a larger
number of alternative solutions. Also, the output is imme-
diately available; it does not have to be returned from a
remote computer center. In addition, the program can be
easily modified and rerun.
Computer Requirements
The microcomputer version of Netsim, designed to run on
IBM-PC compatible machines, runs under either PC-DOS
or MS-DOS, version 2.0 or higher. It requires at least 335
K of memory, exclusive of memory needed for the oper-
ating system. Two floppy disk drives are recommended,
although one will suffice for most problems. A hard disk
drive provides additional flexibility and increases the speed
slightly, particularly with certain options such as printing
the origin-destination table or saving vehicle trajectory
data.
Availability
The microcomputer version will be available later this year
after final testing is completed and a user guide Is
prepared.* Availability will be announced in the UPBeat
newsletter of the STEAM user group. Information
concerning this microcomputer conversion can be
obtained from Mr. James Clark, HTO-23, Office of Traffic
Operations, Federal Highway Administration, Washington,
DC 20590; telephone (202) 426-0411.
2S. Sibley, ‘Use of Netsim for Microcomputers,’’ Office of Implemen-
tation, Federal Highway Administration, Washington, DC, January 1985.
Not yet printed.
PUBLIC ROADS ® Vol. 49, No. 2
REFERENCES
(7) Charles R. Stockfisch, ‘The UTCS Experience,’’ Public
Roads, vol. 48, No. 1, June 1984, pp. 25-29.
(2) E. Lieberman and N. Rosenfield, ‘Traffic Network Analysis
With Netsim—A User Guide,’’ Report No. FHWA-IP-80-3,
Federal Highway Administration, Washington, DC, January
1980.
(3) E. Lieberman and N. Rosenfield, ‘‘Network Flow Simulation
for Urban Traffic Control System—Phase II, Vol. 5, Field and
Emissions Extension,’’ Report No. FHWA-RD-77-45, Federa/
Highway Administration, Washington, DC, October 1977.
Scott W. Sibley is a highway engineer with Gannett
Fleming Transportation Engineers in King of Prussia, PA,
and a Master's Degree candidate at Villanova University.
He performed the work described in this article under a
Research Fellowship Grant from the Federal Highway
Administration at the Turner-Fairbank Highway Research
Center in McLean, VA.
59
aes F .
Se ei cm | ,
eeaens aw
iw ae
2%, ie eae
44: amend
The Herbert S. Fairbank building is part of the Turner-Fairbank Highway
Research Center in McLean, VA.
David K. Phillips, Associate Administrator for
Research, Development, and Technology,
welcomed guests to the ceremony.
Charles F. Scheffey, RD&T Science Advisor,
discussed the history of the Fairbank building.
60
Reopening of the
Herbert S. Fairbank
Building
On May 24, 1985, the Federal Highway Administration
(FHWA) held an open house to mark the reopening of the
Herbert S. Fairbank building at the Turner-Fairbank
Highway Research Center (TFHRC) in McLean, VA. The
reopening followed 6 months of renovations to the
Fairbank building, which is one of the two original
buildings constructed at the highway research center in
the 1940's.
David K. Phillips, Associate Administrator for Research,
Development, and Technology (RD&T), welcomed the
approximately 350 FHWA employees, retirees, and friends
and representatives from highway associations and other
Federal agencies.
Charles F. Scheffey, RD&T Science Advisor, discussed
the history of the TFHRC and introduced Federal Highway
Administrator R.A. Barnhart.
After brief remarks, Mr. Barnhart, with the aid of repre-
sentatives from the Offices of RD&T, cut the ribbon at
the entrance of the Fairbank building to officially
commemorate the renovation.
As part of the day’s festivities, Mr. Barnhart, Deputy
Federal Highway Administrator L.P. Lamm, and FHWA
Executive Director R.D. Morgan joined in a ceremonial
groundbreaking for the Pavement Testing Facility to be
constructed at TFHRC. The facility will include an
accelerated load test facility and two test pavement
sections.
Visitors viewed improvements to the Fairbank building
and toured the laboratories, wind tunnel, highway driving
simulator, demonstration projects exhibits, and U.S.
Highway Technology Exhibit. Outdoor demonstrations by
the Demonstration Projects Division included pavement
Striping, epoxy injections in concrete slabs, a portable
flume, and a borehole camera. Also demonstrated was an
impact test at the Federal Outdoor Impact Laboratory.
September 1985 «© PUBLIC ROADS
\
\ XN rbank
“ts ding
ay
A ribbon-cutting ceremony marked the reopening of the Fairbank building.
Federal Highway Administrator R.A. Barnhart
officiated at the reopening ceremony.
Mr. Barnhart, FHWA Executive Director
R.D. Morgan, and Deputy Federal Highway
Administrator L.P. Lamm participated in the
groundbreaking for the Pavement Testing
Facility to be constructed at the Turner-
Fairbank Highway Research Center.
=
AGojouy2Ia} | AemuByy
The U.S. Highway Technology Exhibit, on display at the Fairbank build-
ing, illustrates highway technology in colorful photographs, by micro=-
computer, and in a videotape.
Pavement striping was demonstrated at the highway research site.
61
PUBLIC ROADS ® Vol. 49, No. 2
Recent
Research
Reports
You Should
Know About
The following are brief descriptions of
selected reports recently published by the
Federal Highway Administration, Offices
of Research, Development, and Tech-
nology (RD&T). The Office of Engineering
and Highway Operations Research and
Development (R&D) includes the Struc-
tures Division, Pavements Division, and
Materials Division. The Office of Safety
and Traffic Operations R&D includes the
Traffic Systems Division, Safety Design
Division, and Traffic Safety Research
Division. The reports are available from
the source noted at the end of each
description.
Requests for items availabie from the
RD&T Report Center should be addressed
to:
Federal Highway Administration
RD&T Report Center, HRD-11
6300 Georgetown Pike
McLean, VA 22101-2296
Telephone: 703-285-2144
When ordering from the National Tech-
nical Information Service (NTIS), use PB
number and/or the report number with the
report title and address requests to:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
62
Pedestrian Signalization
Alternatives, Final Report, Report
No. FHWA/RD-83/102
by Safety Design Division
Pedestrian accidents, traffic and
pedestrian volumes, geometrics, and
signal data for approximately 1,300
signalized intersections in 15 U.S.
cities were analyzed to determine the
safety and operational effects of
various pedestrian signals and signal
timing. The presence of standard-
timed pedestrian WALK/DON’T
WALK signals did not significantly
affect pedestrian accidents. However,
scramble (or exclusive) pedestrian
timing was associated with signif-
icantly lower pedestrian accidents.
Current warrants for traffic signals
based on pedestrian volumes were
evaluated, and an improved warrant
was developed and is recommended
for adoption.
Several new sign and signal alterna-
tives were developed and field tested
to indicate the clearance interval
and to warn of pedestrian-vehicle
conflicts. Alternatives recommended
for inclusion in the Manual on
Uniform Traffic Control Devices for
use at high-hazard pedestrian inter-
sections include the WALK WITH
CAREssianaly) a. YIELDSTOIPEDESs
TRIANS WHEN TURNING regulatory
sign, a PEDESTRIANS WATCH FOR
TURNING VEHICLES warning sign,
and a verbal and symbol pedestrian
Signal explanation sign. A three-phase
pedestrian signal using DON’T
START to indicate the clearance
interval was recommended for
additional testing.
Limited copies of the report are avail-
able from the RD&T Report Center.
September 1985 * PUBLIC ROADS
Relationships Between Traffic
Conflicts and Accidents,
Vols. 1-3, Report Nos.
FHWA/RD-84/041-043
by Safety Design Division
These reports analyze the relation-
ships between traffic conflicts and
accidents as well as expected and
abnormal conflict rates for various
intersection situations. Accidents/
conflict ratios were statistically deter-
mined for several kinds of collisions
for each of four kinds of inter-
sections —signalized high volume,
signalized medium volume, unsig-
nalized medium volume, and unsig-
nalized low volume. These ratios can
be applied to comparable inter-
sections to obtain an expected
accident rate of a specific type after
the appropriate conflict data are
collected. Also, statistical procedures
were developed to determine conflict
rate values that could be considered
abnormally high.
Volume 1, Executive Summary,
highlights the research results and
conclusions. Volume 2, Final Tech-
nical Report, provides research
details, data, and an analysis of
results. Volume 3, Appendixes, con-
tains raw data summaries.
Limited copies of the reports are
available from the RD&T Report
Center.
PUBLIC ROADS ® Vol. 49, No. 2
Fingerprinting Versus Field
Performance of Paving Grade
Asphalts, Report No.
FHWA/RD-84/095
by Materials Division
This report discusses a study to
determine whether there have been
significant changes in the properties
of asphalt cement in recent years,
especially since the 1973 oil embargo.
Nearly 300 asphalt samples were
tested and compared with the FHWA
fingerprint file and other recently
published data. Results indicate that
the temperature susceptibility of
asphalt cements has increased in
recent years. Also, mixtures identified
as tender could not be related to any
single asphalt cement property.
Although heat of immersion tests
may identify asphalts that do not set
properly and therefore are susceptible
to tenderness, more research is
needed to verify this. Finally, current
specification test methods cannot
adequately predict the field perform-
ance of asphalt cement. Because
mixture design and construction
quality control play a major role in
determining the performance of
asphalt cement, the performance of
the asphalt should be evaluated as
part of the overall performance of the
mixture.
Limited copies of the report are avail-
able from the RD&T Report Center.
The Behavior of Piles and Pile
Groups in Cohesionless Soils,
Report No. FHWA/RD-83/038
by Materials Division
This report describes the results of an
indepth literature review to collect
data on instrumented piles driven in
sand and tested under vertical loads.
The load transfer characteristics of
the piles were analyzed without
considering residual stresses. The
results of this analysis then were
correlated with available soil data to
obtain a predictive pile capacity
method that considers residual driving
stresses. Results of this method as
well as conventional and new in situ
test methods then were compared to
actual load test results. Field load
tests on piles in cohesionless soils
will be conducted in a follow-on
study to investigate the new design
method and residual stress theory.
The report should be of interest to
geotechnical and foundation engi-
neers concerned with load transfer
characteristics of pile foundations for
highway structures in cohesionless
soils.
Limited copies of the report are avail-
able from the RD&T Report Center.
63
Pavement Performance Model
Development, Vols. I-IV, Report
Nos. FHWA/RD-84/103-106
by Pavements Division
A computer program was developed
to compute indices of pavement
performance for pavement manage-
ment systems. Inputs to the
computer program include deflection,
distress, roughness, and pavement
description data. Indices computed
for surface condition, structural
capacity, and serviceability may be
combined into a pavement condition
Statistic with probability and matrix
evaluation. Traffic volumes, highway
class, and the statistic define an
overall highway condition rating func-
tion.
The Executive Summary, Report
No. FHWA/RD-84/ 103, briefly
reviews the research. The Final
Model Development, Report No.
FHWA/RD-84/104, and the
Program Documentation Manual,
Report No. FHWA/RD-84/ 105,
provide detailed information on the
computer program. The Roughness
Measurement and Calibration
Guidelines, Report No. FHWA/
RD-84/106, selects a statistic for
generalized roughness index and
presents a procedure that can be
used to calibrate roughness measure-
ments in the long-term monitoring
program.
The reports may be purchased from
NTIS.
64
Corrosion Susceptibility of
Internally Reinforced Soil
Retaining Structures, Report No.
FHWA/RD-83/105
by Structures Division
This report assesses the state-of-
knowledge of metal corrosion in rein-
forced soil retaining walls. Four Rein-
forced Earth Walls with concrete
facings were studied to determine
corrosion susceptibility. These four
structures were between 6 and 11
years old and were exposed to severe
environments such as high chloride
and pH. It was found that two of the
four structures may have corrosion
problems that could reduce their
design life. One of these structures is
in a marine environment and uses
aluminum alloy strips. The other
structure has backfill material with
low resistivity and high pH value that
surrounds the galvanized steel strips.
Additional field studies are needed to
assess the magnitude of the prob-
lems, and further research is needed
to determine the safe limits of the
reinforced earth concept.
The report may be purchased from
NTIS.
Streambank Stabilization
Measures for Highway Stream
Crossings, Executive Summary,
Report No. FHWA/RD-84/099;
Streambank Stabilization
Measures for Highway Engineers,
Report No. FHWA/RD-84/100; and
Design of Spur-Type Streambank
Stabilization Structures, Report
No. FHWA/RD-84/101
by Structures Division
These reports discuss the findings of
a research study on the application
and usefulness of spurs, groins, and
other countermeasures for stream-
bank stabilization in the vicinity of
highway stream crossings. Report
No. FHWA/RD-84/099 summarizes
the findings discussed in the other
two reports.
Report No. FHWA/RD-84/ 100
discusses erosion processes in
channel bends and methods of
controlling this erosion, identifies
useful flow control and streambank
stabilization structures, and provides
guidelines for selecting an appropriate
flow control or streambank stabiliza-
tion countermeasure for a particular
field design condition. Some design
information for specific counter-
measures also is included.
Report No. FHWA/RD-84/101 details
the applicability and design of spur-
type flow control and streambank
stabilization structures. Design guide-
lines for establishing spur permea-
bility; the required extent of protec-
tion; spur length, spacing, orienta-
tion, height, and crest profile; and
the shape of the spur tip or head are
presented. An example is given for a
recommended procedure for estab-
lishing the geometric layout of spurs
within a spur scheme.
Limited copies of the reports are
available from the RD&T Report
Center.
September 1985 ¢ PUBLIC ROADS
New Research in Progress
The following new research studies
reported by FHWA’s Offices of Research,
Development, and Technology are
sponsored in whole or in part with Federal
highway funds. For further details on a
particular study, please note the kind of
study at the end of each description and
contact the following: Staff and adminis-
trative contract research— Public Roads
magazine; Highway Planning and Research
(HP&R)—performing State highway or
transportation department; National Coop-
erative Highway Research Program
(NCHRP) — Program Director, National
Cooperative Highway Research Program,
Transportation Research Board, 2101
Constitution Avenue, NW., Washington,
DC 20418.
PUBLIC ROADS ® Vol. 49, No. 2
FCP Category 1— Highway
Design and Operation for
Safety
FCP Project 1P: Night Visibility
Title: Develop and Evaluate
Traveling Photometer. (FCP No.
41P3193)
Objective: Design and build a
photometer that can be used at
highway speeds to measure the
reflectivity of raised reflective pave-
ment markers and reflective lane
lines. Develop an algorithm for trans-
lating photometer data into an eval-
uation of the adequacy of lane line
delineation. Construct and program
an onboard data acquisition system
for evaluating and recording lane line
adequacy and location information for
input to a pavement marking
management system.
Performing Organization: Cali-
fornia Department of Transportation,
Sacramento, CA 95807
Expected Completion Date:
June 1986
Estimated Cost: $60,000 (HP&R)
FCP Project 1T: Roadside Safety
Hardware
Title: Vehicle Downsizing and
Roadside Safety Hardware. (FCP
No. 51T2982)
Objective: Assess the performance
of selected existing highway safety
appurtenances and roadside features
with passenger vehicles below 1,800
Ib (0.82 Mg). Project the limits of
vehicle characteristics that can be
accommodated safely through
improvements in current hardware
and roadside features.
Performing Organization: Texas
A&M Research Foundation, College
Station, TX 77842
Expected Completion Date:
October 1987
Estimated Cost: $150,000 (NCHRP)
65
FCP Category 2—Traffic
Control and Management
FCP Project 2L: Electronic
Devices for Traffic Control
Title: Lightning-Protection Hard-
ware and Techniques for Elec-
tronic Traffic Control Equipment.
(FCP No. 32L1232)
Objective: Evaluate existing stand-
ards and guidelines for lightning and
electrical transient protection of elec-
tronic devices, including grounding
and bonding of power systems and
appurtenant structures (lightning
rods, ground rods, and shielding) and
transient and surge protection of
power and signal system lines (fuses,
filters, varistors, and gas discharge
devices). Identify the standard
practice for applying each protective
device, balancing initial hardware and
installation costs against the proba-
bility of equipment damage, malfunc-
tion, and repair cost.
Performing Organization: Peer
Consultants, Inc., Rockville, MD
20852
Expected Completion Date:
February 1986
Estimated Cost: $48,470 (FHWA
Administrative Contract)
66
FCP Project 2Q: Urban Network
Control
Title: Enhancement of the Value
Iteration Program for Actuated
Signals. (FCP No. 4201222)
Objective: Extend the VIPAS
program to include additional left turn
geometrics. Collect field data to calli-
brate, validate, and test VIPAS.
Reprogram to increase the modulari-
zation of some current subroutines.
Performing Organization: Univer-
sity of Pittsburgh, Pittsburgh, PA
15260
Funding Agency: Pennsylvania
Department of Transportation
Expected Completion Date:
August 1986
Estimated Cost: $174,985 (HP&R)
Title: Graphic Displays for the
Integrated Traffic Data System
(ITDS). (FCP No. 3202322)
Objective: Develop and integrate
graphics software to the data base
portion of ITDS to ease the task of
loading and maintaining the data
base. Develop query software to
allow for the generation of reports
based on the information stored on
the data base.
Performing Organization: Oak
Ridge National Laboratory, Oak
Ridge, TN 37831
Expected Completion Date:
April 1987
Estimated Cost: $94,000 (FHWA
Administrative Contract)
FCP Project 2Z: Implementation
of Traffic Control R&D
Title: Integrated Traffic Data
System (ITDS) Maintenance and
Support. (FCP No. 32ZQ108)
Objective: Develop a microcomputer
data base system for traffic engi-
neering data. Use data to execute
mainframe programs such as
SIGOP-IIl, TRANSYT-7F, and
NETSIM without coding input data
for each program. Make the ITDS
more user friendly and provide assist-
ance to users on all aspects of the
software.
Performing Organization: Oak
Ridge National Laboratory, Oak
Ridge, TN 37831
Expected Completion Date:
April 1987
Estimated Cost: $50,000 (FHWA
Administrative Contract)
FCP Category 4— Pavement
Design, Construction, and
Management
FCP Project 4A: Pavement
Management Strategies
Title: Improved Prediction of
Equivalent Axle Loads. (FCP No.
34A1022)
Objective: Develop procedures to
forecast the total number of equiva-
lent axle loads over the design period
in various load groups. Investigate
how truck volumes and vehicle miles
(kilometers) of travel have varied with
economic output and how axle load
distribution has changed with legisla-
tive changes.
Performing Organization: Texas
A&M Research Foundation, College
Station, TX 77843
Expected Completion Date:
December 1986
Estimated Cost: $121,320 (FHWA
Administrative Contract)
September 1985 ¢ PUBLIC ROADS
——
FCP Project 4C: Design and
Rehabilitation of Flexible Pave-
ments
Title: Layer Coefficients in Terms
of Performance and Mixture Char-
acteristics. (FCP No. 44C2074)
Objective: Conduct a literature
review and determine data require-
ments. Collect and analyze both field
and laboratory data. Determine layer
equivalencies for different asphalt
concrete mixtures, and model pave-
ment performance to evaluate the
effects of seasonal and climatic
factors.
Performing Organization: Purdue
University, West Lafayette, IN 47907
Funding Agency: Indiana Depart-
ment of Highways
Expected Completion Date:
April 1988
Estimated Cost: $7,540 (HP&R)
PUBLIC ROADS ® Vol. 49, No. 2
FCP Project 4E: Construction
Control and Management
Title: Methodology for Cost
Comparison Between Department
and Contractor Performance for
Various Department Operations.
(FCP No. 44E3096)
Objective: Develop methodology
and a model for comparing costs of
contracting for services with costs for
using Pennsylvania Department of
Transportation staff. Examine mainte-
nance, bridge and highway design,
and inspection of bridge and highway
construction services.
Performing Organization: Deloitte
Haskins and Sells, Philadelphia, PA
19102
Funding Agency: Pennsylvania
Department of Transportation
Expected Completion Date:
April 1986
Estimated Cost: $25,000 (HP&R)
FCP Category 5— Structural
Design and Hydraulics
FCP Project 5A: Bridge Loading
and Design Criteria
Title: Prestressed Concrete Inter-
mixed With Steel Beams for
Bridge Widening. (FCP No.
45A3242)
Objective: Determine if practical
problems related to behavior and
long-term performance are caused by
the combinations and intermixture of
prestressed concrete beams and steel
beams in the same span. Identify
these problems and recommend
concrete slab design and live load
distribution to longitudinal beams
with respect to mixed girder support
systems.
Performing Organization: Tulane
University, New Orleans, LA 70118
Funding Agency: Louisiana Depart-
ment of Transportation and Devel-
opment
Expected Completion Date:
February 1986
Estimated Cost: $74,060 (HP&R)
Title: Redundancy of Welded
Steel I-Girder Bridges. (FCP No.
45A4052)
Objective: Develop and implement a
framework to facilitate decisions
regarding the realistic adequacy of
welded steel |-girder bridges to resist
catastrophic failure from the fracture
of a critical member. Use computer
modeling to develop meaningful
quantitative comparisons of potential
collapse mechanisms.
Performing Organization: Lehigh
University, Bethlehem, PA 18015
Funding Agency: Pennsylvania
Department of Transportation
Expected Completion Date:
December 1986
Estimated Cost: $149,930 (HP&R)
67
FCP Project 5H: Highway
Drainage and Flood Protection
Title: Channel Widening Process
and Long-Term Channel Geometry
in Adjusting Streams in West
Tennessee. (FCP No. 45H1392)
Objective: Perform extensive
channel modifications, and collect
information along newly dredged
reaches to establish the magnitude
and extent of the modifications, test
the ability of a quantitative model,
and predict resultant channel
responses and instability. Obtain bed
and bank material samples and data
on channel geometry and vegetation
at all sites.
Performing Organization: U.S.
Geological Survey, Nashville, TN
37203
Funding Agency: Tennessee
Department of Transportation
Expected Completion Date:
September 1987
Estimated Cost: $100,000 (HP&R)
Title: Design of Depressed Invert
Culverts. (FCP No. 45H3182)
Objective: Review current guidelines
for designing a culvert with a
depressed inlet to enhance fish
passage.
Performing Organization: Univer-
sity of Alaska, Fairbanks, AK 99701
Funding Agency: Alaska Depart-
ment of Transportation and Public
Facilities
Expected Completion Date:
September 1986
Estimated Cost: $8,770 (HP&R)
68
Title: Hydrologic Criteria for Fish
Passage With Regard to South-
east Alaska. (FCP No. 45H3802)
Objective: Develop small streamflow
relationships between frequency,
magnitude (high or low), duration,
and season. Include orographic, mari-
time, and elevation influences from
analysis of existing data from certain
watersheds in southeast Alaska.
Performing Organization: Univer-
sity of Alaska, Fairbanks, AK 99701
Funding Agency: Alaska Depart-
ment of Transportation and Public
Facilities
Expected Completion Date:
September 1986
Estimated Cost: $10,180 (HP&R)
FCP Project 5Q: Bridge Mainte-
nance and Corrosion Protection
Title: Effectiveness of Concrete
Bridge Deck Asphalt Membrane
Protection. (FCP No. 4502612)
Objective: Evaluate further through
field testing the performance of
waterproofing membrane systems in
service in the State of Washington.
Select sites that had satisfied existing
criteria regarding the application of
membrane systems at the time of
waterproofing.
Performing Organization: Wash-
ington State Transportation Center,
Seattle, WA 98195
Expected Completion Date:
February 1986
Estimated Cost: $37,000 (HP&R)
U.S. Government Printing Office: 1985—461-830/ 10005
FCP Category 9—R&D
Management and Coordina-
tion
FCP Project 9C: Highway Safety
Programs Support
Title: Highway Simulator (HYSIM)
Maintenance and Support. (FCP
No. 39C3122)
Objective: Maintain HYSIM hard-
ware and software, and modify hard-
ware and/or software to meet
requirements of specific experiments.
Assist in testir.3 subjects in HYSIM
studies, calibrate and operate simu-
lator during experimentation, and
assist in data reduction. Incorporate
general-purpose hardware/software
into HYSIM to enhance research
capability.
Performing Organization: ENSCO,
Inc., Springfield, VA 22151
Expected Completion Date:
April 1986
Estimated Cost: $159,800 (FHWA
Administrative Contract)
September 1985 e PUBLIC ROADS
RD&T Outstanding Technical Accomplishment Award Presented
Dr. Samuel C. Tignor was the recip-
ient of the 1985 award in the annual
outstanding technical achievement
competition held among the
employees of the Federal Highway
Administration’s (FHWA) Offices of
Research, Development, and Tech-
nology. The award covers the docu-
mentation of any technical
accomplishment, which may be a
publication, technical paper, report,
film, or package; an innovative engi-
neering concept; an instrumentation
system; test procedure; new specifi-
FHWA Research, Development, and Technology Implementation Catalog
cation; mathematical model: or
unique Computer program. Each
eligible candidate is judged on excel-
lence, creativity, and contribution to
the highway community, general
public, and FHWA.
Dr. Tignor, Chief of the Traffic Safety
Research Division, Office of Safety
and Traffic Operations Research and
Development, received the award for
his film ‘‘Traffic Management for
Freeway Incidents.’’ This 17-minute
film promotes the rapid removal of
by Office of Implementation
This catalog, which is revised
periodically, lists selected publica-
tions, visual aids, computer
programs, and training materials that
are available as part of the FHWA
Implementation Program. Items are
listed alphabetically under program
areas. Subtitles and series are shown
separately under the main item
heading. Indexes at the back of the
catalog are arranged alphabetically,
by program area, and by report
number.
Items in the catalog are available
directly from the source indicated
under the ‘‘Availability’’ heading in
each listing. Some items are available
without charge to qualified individuals
and agencies; others are available on
a loan basis only.
Copies of the catalog are available
from the Federal Highway Adminis-
tration, RD&T Report Center,
HRD-11, 6300 Georgetown Pike,
McLean, VA 22101-2296; telephone
(703) 285-2144.
freeway incidents (for example,
spilled loads or disabled vehicles) and
describes low-cost solutions that
highway, police, fire, and other local
agencies can use to improve traffic
management, safety, and control at
incident sites. Traffic management
approaches for both simple and
complex incidents are illustrated in
the 16 mm film. Footage is incorpo-
rated from several major metropolitan
areas in the United States. Currently,
the film is being used in a National
Highway Institute training course.
Q
US. Department of Transportation
Federal Highway Administration.
Research, Development, and
Technology :
Office of Implementation
FHWA
Research, Development,
and Technology
Im plementation Catalog
Reets
#
March 1985
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