scientific street lighting
The maximum of service
at the minimum of cost.
Trend of Street Lighting Practice
Increase in the speed and volume of street traffic and the use of our streets at night, has brough about an
advance in the standards of what constitutes satisfactory street lighting. This advance has been most marked
in respect of the principle business and traffic streets, but there is also a material, if less spectacular advance
in residential standards.
Improved street lighting service is being attained in part through improvements in the equipment, in part through
advances in engineering knowledge resulting in the more effective use of available equipment, and in part through
increased public expenditure. It is important to note that, in localities where the movement has been intelligently
led, the public has been very willing to adopt a scale of larger expenditure and has not been content only with
improved service made possible by advances in the science.
It should be the part of the electrical industry to furnish intelligent and aggresive leadership in the movement toward
better street lighting. Every opportunity should be made use of to impress this upon lighting committees, and
upon the public in general. Public recognition, impelled by changed social conditions, and the adoption of much higher
standards of street lighting service, will result in the movement being greatly quickened to the advantage alike of the
public and the electrical industry.
The foregoing paragraphs present the social and the commercial aspects of the trend of street lighting practice.
On the engineering side, the trend of practice is toward :-
- Closer spacing.
- Greater mounting heights.
- Higher intensity values.
Closer Spacings. A street light is usually placed at each street intersection. An intermediate light
is necessary for first-class service when the length between intersections is more than 16 times the mounting height.
Two intermediate lights are necessary for first-class service when the lengths between intersections exceeds 30 times
the mounting height. The spacing of units should not greatly exceed 12 times the mounting height.
Greater Mounting Heights. There is a gradual but nevertheless positive tendency towards greater
mounting heights in street lighting, and 15 feet should be regarded as a minimum. In business streets 25 to 30
feet are generally the most satisfactory heights.
Higher Intensities. For good practice in street lighting the following approximate average intensities
of illumination should be provided; in addition to which the spacing should be sufficiently close to provide a
reasonable uniformity of illumination, and the following figures are based on the assumption that the installation is
not characterised by excessive glare.
Lighting intensities required to make Streets Safe and Convenient by night.
||0.05 to 0.10
|Arterial streets, outside of retail business districts, carrying much motor traffic and little pedestrian traffic
||0.12 to 0.15
|Business thoroughfares and roads carrying greater motor traffic
||0.20 to 0.30
|Main business thoroughfares and promenade streets
||0.40 to 0.50
It should be remembered that, for promenade streets higher intensities than those given may be desirable for advertising value.
The intensities above represent only the values required to make the street as convenient and as safe for use by night
as by day.
"HOLOPHANE, SOWEST, London"
"VICTORIA, 2491, 8258."
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