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.