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Full text of "The history and development of street lighting systems in the suburbs of Washington / by William A. Harmon"

THE HISTORY AMD DEVELOPMENT OF STREET LIGHTING SYSTEMS 
IN THE SUBURBS OF WASHINGTON 

presented to 

THE TAU BETA PI HONORARY ENGINEERING FRATERNITY 
UNIVERSITY OF MARYLAND 



by 



William A. Harmon, '35 
January 13, 1934. 



SUMMARY 

Street lighting was desired in the suburbs of 
Washington as a protection to life and property, as a boost 
to civic pride and publicity, as an aid to the merchants, 
and finally as a method of facilitating traffic at night. 

In the days before the suburban towns had street 
lighting systems, it was a general practice of the residents 
to run a line from their houses out to a lamp hung over the 
front gate. Then in 1908 Chevy Chase is found to have a 
street lighting system of 58 multiple lamps. In 1912 Takoma 
Park had a series system of 111 lamps. In 1913 Hyattsville, 
along with Mt. Rainier, followed with series street lighting. 
Electrical power was purchased under individual contracts 
from the Potomac Electric Power Company. New contracts 
were issued in 1921 to all the suburban towns. 

The development in street lighting is marked by 
an increase in illumination, the number of lamps and the 
candle power of each lamp. Together with this, there has 
been a steady improvement in reflecting and refracting 
devices as well as in the character of the lamp fixtures 
and diffusing glassware. All of these factors have led to 
a better distribution of light and consequently a more 
efficient street lighting By stem. The series system has 
replaced the multiple system almost entirely. 



- 3 - 

The growth of street lighting systems has been 
necessarily slow in the suburbs due to the comparatively 
limited town treasuries, but it has been a steady march in 
the right direction - that is, toward perfection in street 
lighting. 



-1- 



FURFOSE OF STREET LIGHTING 








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From the first, street lighting systems were de- 
sired as a protection to life and property. Tests were 
actually conducted to show that lighted streets were of 
real value In preventing and detecting crime. The people 
"began to have more confidence in venturing out on the Btreets 
at night, and hand in hand with that confidence came the 
growth of the community. Good street lighting was a great 
boost to the suburbs of Washington. It instilled a feeling 
of civic pride among the residents and gave the community 
good publicity. Then, too, it was an aid to merchants. The 
merchant's prime aim "being to sell merchandise, he could set 
forth attention- get ting and interest-compelling window dis- 
plays for the people on the sidewalks. But how was he to be 
sure that there would be people on the sidewalks in the 
vicinity of his store unless there was an adequate street 
lighting system to attract them? 



With the coming of the automobile in great numbers, 
running at speeds far in excess of the old horse-drawn ve- 
hicle of earlier days, the value of good street lighting in 
the facilitation of traffic became more evident. In the 



-3- 
suburbs the intensity of traffic was not nearly as great as 
in the city. Nevertheless, it became necessary to have 
street illumination of sufficiently high order to enable 
the driver of the automobile to see objects on the road 
and act before disaster overtook him. It was proved that in 
1920, 18$ of all deaths at night due to traffic accidents 
could have been eliminated if adequate street lighting had 
been available. People began to realize that they were pay- 
ing considerably more money as a result of accidents and 
deaths in traffic than they were in attempting to reduce 
these losses. It was natural that a steady growth in street 
lighting should follow. 

HISTORICAL 

In the early days, when people in the suburbs of 
Washington had just received electric lighting in their 
homes but had no street lighting system, it was the general 
practice to string a wire from their houses out to an elec- 
tric light hung over their front gates. The gas light was 
very seldom seen in the BUburbe, the development in illumi- 
nation being directly from the kerosene lamp to the electric 
light in most instances. 

The general system used in lighting the homes by 
electricity was of the multiple type. When the first street 
lighting systems were installed in the suburbs it was only 



-3- 
natural that they would be multiple. It was the more famil- 
iar system and probably the best for street lighting on a 
small scale as it then was. Thus in 1908 Chevy Chase had 
fifty-eight multiple lamps. In the next year or two the 
other suburbs installed simple multiple systems - at least 
to illuminate the main business street. The first series 
lights started in Somerset in 1911. Then in 1913 Talcoma 
Pari; stepped ahead with a new series system of one hundred 
eleven lamps. Hyattsville followed shortly afterward in 
1913 along with lit. Rainier. 

Each of these suburban towns bought electricity 
from the Potomac Electric Power Company of Washington, D. C. 
under individual contracts. Each contract was made under 
varying circumstances and consequently the conditions of 
each contract were slightly different. Naturally, some dis- 
satisfaction arose from the towns whose people thought they 
were not getting as fair a deal as Borne other town. Finally 
in 1921 the Potomac Electric P wer Company, in an effort to 
standardize conditions, came to an agreement with the 
suburbs as a whole, revoked the old contracts and gave them 
all new contracts which were more uniform and which are 
still in effect. At present the series system has almost 
entirely replaced the multiple system, although there still 
remains a small section of Chevy Chase illuminated by the 
multiple lamps. 



-4- 

REQUIREMMTS OF SUBURBAN LIGHTING 

Suburban streets may be divided roughly into two 
classes: residential streets and business streets. The 
requirements for an ideal lighting system of a residential 
street in the BUburbs are: (1) adequate lighting so that 
pedestrians and householders may have a feeling of security; 
(3) there should be no dark pockets on the streets, lawns, 
or between the houses; (3) one Bhould be able to recognize 
road obstructions, transverse and parallel traffic, turns, 
dead ends, steep grades, railroad tracks, etc.; (4) con- 
siderable care must be taken to avoid objectionable light 
on the houses; (5) the type of fixture used should be in 
keeping with the character of the neighborhood. The re- 
quirments for an ideal suburban business street are: (1) a 
moderately high level of illumination to increase business, 
and to prevent accidents and crime; (2) quality with regard 
to color diffusion of light and freedom from glare; (3) a 
distribution so controlled as to give sufficient illumina- 
tion on the street surface, and at the same time allow 
enough light to strike the buildings and make visible the 
architectural details; (4) units of such a character as to 
present an attractive appearance both by day and night, to 
harmonize with the character of the building, and to carry 
out the traditions of the town. 



-5- 
The development of street lighting in the suburbs 
of Washington has ever been to fulfill the above requirements 
and to some day reach the ideal in street lighting. From 
the early days there has been a steady increase in illumina- 
tion by gradually having more lamps and more candle-power 
per lamp. Along with this is an improvement in reflecting 
and refracting devices as well as in the character of the 
lamp fixtures and diffusing glassware. The principles of 
street lighting systems, however, are essentially the same 
as they were when the systems were first installed in the 
suburbs . 

STREET LIGHTING SYSTEMS • 

There are only two general types of street light- 
ing systems; namely, the multiple and the series systems. 

MULTIPLE SYSTEM 

The earlier type of street lighting introduced in 
the suburbs was the multiple system. It is the system with 
which the average layman is more familiar. It is the type 
of wiring prevalent in our homes, stores, factories, etc. 
Since a number of lamps are in a parallel arrangement, the 
total current in the circuit is the Bum of the current 
passing through each lamp. Any one lamp may burn out with- 
out affecting any other in the system. It is important 



-6- 
that the proper voltage is impressed upon all the lamps; 
otherwise they may fall below the rated life output. It is 
necessary to have heavy wire, comparatively short lines, or 
extra feeders in order to cut down the voltage drop along 
the line. Sometimes it is necessary to put a booster or 
regulator near the end of the line. 

When burned, the filament of any lamp gradually 
vaporizes and the filament vapor deposit on the surface of 
the bulb caueeB blackening. This vaporization causes the 
diameter of the filament to decrease , thus increasing the 
resistance and decreasing the current. The light output, 
then, of a multiple lamp decreases Throughout life due to two 
related factors - bulb blackening and decrease in light out- 
put of the filament. 

In the early days there was a so-called "radial 
feeder" system for lighting multiple street lamps. Under 
this scheme a power transformer would serve a locality or 
group of houses and would be isolated from the others. Then 
when anything went wrong, the whole locality was in dark- 
ness. Also, the further from a transformer a house was lo- 
cated the lower the voltage and the lower the light output 
from the lamp. 

Under the more recent "network* idea, all trans- 
formers of an AC system and the branch currents of a DC 



-7- 
system are tied together in such a way that an ordinary 
failure does not materially affect the current supply to 
any locality. Furthermore, the voltage throughout the whole 
system is more uniform and has fewer and less violent 
fluctuations, thus assuring a proper voltage supply to the 
lamps. Multiple street lamps may toe connected through a 
switch to the supply and turned on and off manually, or may 
be operated as a branch circuit through a pilot wire. 

SERIES SYSTEM 

In the series circuit which has come into general 
use in the BUburtos of Washington, the line current flows 
successively through each lamp of the circuit, or, where 
local current or auto transformers are used, through the 
primary coils so that the same line current passes through 
each unit as contrasted to the subdivision of current in the 
multiple system. The line current must therefore be kept at 
its rated value. This is done with constant current trans- 
formers. 

Necessarily if the line current should be broken 
at any point, all of the lamps on that circuit would be ex- 
tinguished. This was a great disadvantage in the early 
series systems and was probably the reason for the popu- 
larity of the multiple systems in the early stages. It 



-8- 
became a universal practice to provide a cut out as a shunt 
across each lamp so that whenever a lamp failure tends to 
open the current, the voltage impressed upon the insulating 
film punctures the film. In this manner the lamp is short 
circuited and electrical supply is maintained for all other 
lamps of the circuit. 



i 



PR i WARY 
LEADS 






Lc=n 



re 



-nmw^-, 



FILM 
CUTOUT 



AU TOTRANS. I L. TRANS 



Schematic diagram of a simple series system. Provision must be made so thai when a 

lamp Tails, lli<- circuit will maintain its continuity. In the film cutout, the film 

is punctured due to tlic high momentary voltage across the filament. 

In the ease of the auto-transformer or the EL transformer, 

failure of the lamp does not affect the circuit. 



Inasmuch as there is a constant current flowing 
continuously through a series circuit it is essential that 
the lamps used be especially built for this purpose. In 
general these lamps are of the gas-filled type having fila- 
ments manufactured to close specifications as regards current 
capacity. This is in contrast to multiple lamps about which 
specifications emphasize voltage accuracy. Due to the fact 
that as the filament vaporizes its diameter decreases, the 
lamp offers a higher resistance to the current and hence 
generates more light to offset the blackening effects. There- 
fore the lamps for direct operation on series circuits give 
approximately 100$> rated initial light throughout life. This 



-9- 
is a considerable advantage of the series system over the 
multiple system, and was one of the reasons for the series 
lamps taking the place of multiple lamps in the suburbs of 
Washington. 

Series lamps have been steadily improved in re- 
cent years* They now have a nominal life of 1350 hours, 
and are rated in amperes and lumens. In series street 
lighting a 6.6 ampere circuit is used very widely. The fol- 
lowing size lamps are furnished at this current capacity! 
600, 800, 1000, 2500, 4000, and 6000 lumens. If an IL 
transformer is placed on the line pole it is possible to get 
the following size lamps: 4000 lumens - 15 amperes, 6000 
lumens - 20 amperes, 10,000 lumens - 20 amperes. The trans- 
former serveB the double purpose of transforming the current 
from line amperage to that of the lamp and of providing in- 
sulation, the primary and secondary coils being entirely 
separate. The transformer is mounted right on line pole or 
in the base of the lamp post as shown in the diagrams. 




L&TTip Post — 




Leads to Lamp 



Wiped or Water-, 
~ rpefeci Taped Joint 



gli Vottngt 

"es Circuit 



-10- 



DISTRTBUTION OF LIGHT 



Ever since street lights were first introduced in 
the suburbs there has been development in the distribution 
of light by street lamps all of which have tended to increase 
the efficiency of illumination. The distribution of light 
about a bare lamp depends upon the position of burning and 
shape of the filament. While it is true that any type of 
globe surrounding a lamp will reduce the total light output 
of the unit, it is also true that proper equipment reduces 
glare, improves appearance and protects the light from the 
elements. This enclosing glassware was first opal, but the 
more recent tendency has been toward the rippled type be- 
cause it presents a more pleasing appearance and gives cer- 
tain sparkle and animation to the light. The amount of 
light absorption depends upon the density of the glass and 
will vary from 10 to 30^. 

In the early days it was 
realized that for the purpose of 
street lighting, all the light going 
above the level of the lamp was void. 
Hence the need of a reflector was 
realized. One of the earlier types 
of reflectors which was greatly used 
throughout the suburbs was the radial 



w'TM\BApe-u>Mp 
andaEjWSsing Glassware: 




-11- 

wave type reflector. This consisted simply of a metal plate 
with waves in it and a shiny finish on the surface of the 
reflector where the light from the lamp struck. The purpose 
of the waves was to scatter the light over a wider street 
surface than the flat disc would. The radial wave type 
after introduced was used in the suburbs to the almost ex- 
clusion of other types. The only developments in this type 
were: the perfection of a porcelain enamel finish on the 
reflector and improvements in insulation around the socket. 
Gradually this type is being replaced by either a new re- 
flector type known as the "eternalite" unit or "eternalite 
globe" lamps in which the reflectors are entirely porcelain. 

REFRACTORS 

Refractors are combinations of pieces of glassware 
each molded into a series of prisms which refract the light 
and redirect it toward the surface of the street. There are 
two classes of distribution with refractors j namely, symetri- 
cal and non-Byrne trieal distribution. The non-symetrical re- 
fractors, , in addition to redirecting the upward light down, 
direct most of it on the actual 

road surface rather than on m^*- ^v 
sidewalks, lawns, etc. This Jp \ 

control of the distribution of m I 

light has been a great develop- ~---« «- — — ^— - 

Dome Refractor -Non-symmetrical 

ment in street lighting. Two 



-12- 
types of refractors are the 
dome and bowl types. The dome 
type is simpler and is more 
widely used in the suburbs. 




Howl Refractor Xon-symmetrica 



BRACKETS 



Brackets are used to hold the fixtures to the line 
poles and at first were very simple in design. Gradually, in 
attempt to beautify the fixture, the bracket became more and 
more ornate. The tendency in recent years, on the other 
hand, is toward a plain but substantial bracket. At present 
in the suburbs there are two predominant types - the bent 
bracket and the straight bracket. Both are shown in the 
accompanying picture with the mounting heights also given. 








m m m 



< 




-13- 

Experience has taught us that within certain limits the 
higher we place the source of light the better the illumina- 
tion. The spacing of lamps bears a definite relation to 
the mounting height. The empirical rule accepted by most 
engineers is that the spacing between lamps must not exceed 
eight times the mounting height. 

PRESENT DAY FIXTURES 



At present there are three distinct groups of light- 
ing units in the suburbs. They are as follows: (1) lamp 
post lighting for the main business street and thoroughfare, 





(2) glass enclosed fixtures of the "eternalite globe" type 
are placed on the line poles on secondary streets adjacent 
to the main thoroughfare, and sometimes on line poles be- 
tween street car tracks, 



-14- 






(3) either the radial wave reflector or the eternalite reflec- 
tor type witn the "bare lamp are placed on the residential 
streets of more or less minor importance. 



W~ 





COSTS 



The early lighting unit similar to the radial 
wave reflector type cost |3.90 complete. Now the prices 
have gone up so that we find that the radial wave reflector 
unit costs either $9.00 or $9.50 and the lighting units 
with enclosing glassware cost either |13.00 or $13.50. The 



-15- 
The price depends upon whether the straight or bent bracket 
type is used - the straight bracket being $.50 cheaper, and 
of course the lamp post variety is a great deal more expen- 
sive. It is evident that street lighting in the suburbs 
could not reach perfection all of a sudden. The town 
treasuries have always been too limited for that. It has 
been the aim, though, to steadily progress toward the ful- 
fillment of ideal requirements and that some day the dream 
of a perfect lighting system for the suburbs of Washington 
may become a reality. 











B IBLIOGRAFHY 








LIGHTING 


DATA 


- BULLETIN LD144A 
















Edison Lamp Works 


of G. E 


. Co. 














t 
i 


Mr . Lockwood 


- Chief 


Engineer 






P. 


E. 


P. 


CO.' 
t 


Distribution 


Department - 


Engineer 


Divi 


sion 








t 


Mr. Barnes - 


General 


Sales Manager 







WASHINGTON OFFICE OF GENERAL ELECTRIC CO. 
MR. DODD - Town Clerk, Takoma Park.