Street Lighting

Abstract

THE improvement in modern street lighting is largely due to the appointment of public lighting engineers whose whole time is devoted to the work. They pay attention to details which have been previously overlooked or neglected. In Electrical Industries for June 15 there is a paper on modern street lighting by Haydn T. Harrison which brings this out clearly. The outstanding advances took place several years ago, gas and the arc lamp being two of the earliest. The invention of gas mantles largely stopped the use of luminous gas. They also prevented the adoption of the carbon filament electric lamp. The invention of the gas-filled lamp was the last notable step forward. The rapidly increasing use of electricity for street lighting at the present time is due not so much to the efficiency of these lamps as to the fact that light can be distributed from them in any required direction by simple optical means. Hence the most notable feature of modern street lighting is the large number of electric lamps fitted with reflectors or glassware designed specially for distributing the total light most efficiently. The motor vehicle head-light is an excellent example of the adaptability of the gas-filled electric lamps. These lamps only take 20 or 30 watts—the same as a small house lamp. By suitable reflections they produce a beam of light in front of the car which enables the driver to see objects to be avoided on the road 100 yards in advance. No other commercial source of light could be made to do the same thing. In modern street and road lighting, the tendency whenever there is a change of system is to raise the height of the lamps. This improves both the illumination on the road surface and the visibility, except when the weather is very foggy.