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.

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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.

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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

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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

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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.

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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.

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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

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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

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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

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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.

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PR i WARY
LEADS

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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

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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

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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:

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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

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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

<

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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,

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(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

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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.