MODERN STREET LAMPS

Taranaki Daily News, 14 March 1935, Page 11

MODERN STREET LAMPS

DISCHARGE PRINCIPLE EXPLANATION BY AN EXPERT. FACTORS TO BE CONSIDERED. EFFICIENCY IN USE OF POWER. An explanation of factors which must be taken into consideration in deciding upon any of the modem systems of street lighting has been supplied by an expert attached to the New Plymouth. Borough Council staff. The council is giving serious consideration to the installation of a Neon system of blue lighting in the main business area of the town and on Tuesday night the electricity department gave a demonstration of several new types of street illumination. The. main factors which govern modem street lighting include, states the council’s officer, visibility of objects on the roadway, visibility of objects on the footpath and distribution of illumination.

Modem rapid moving traffic requires a high intensity of illumination, so that objects on the roadway are directly lighted and clearly visible and accidents may be avoided. A well-lighted road will also give a relatively high intensity of light on the footpath, so that objects will be seen by direct illumination as in the case of the roadway.

One of the most modern types of street light developed is the electric discharge lamp. In the discharge lamp the light comes from a column of vapour made luminous by the passage of. the electric current. This in in contrast to the filament type lamp in general use, where the light is produced by the heating of the wire filament to incandescence. The advantage of the discharge lamp lies in the fact that over two and a-half times the quantity of light is produced for the equivalent power consumed by the gas-filled or half-watt lamp. This remarkable efficiency outweighs any slight objection due to the slightly unusual colour effect. Different mixtures used in the vapour of the lamp produce different colours, mercury and some other vapours causing the light to appear bluish-white. Sodium produces a yellow light. Any attempt, however, to produce artificial daylight, results in a marked loss of efficiency and the types demonstrated on Tuesday night represented each maker’s idea of a suitable street lighting colour and are the result of much research by the manufacturers to produce a suitable lamp of high efficiency. As showing their success in this direction, it may be mentioned that the British Ministry of Transport has given its full approval of the system and one of the firms whose lamps were, displayed, have made some 62 installations in England alone, one being over seven miles in length with no less than 224 lanterns. This should serve to illustrate that the system is well out of the experimental stage and it is of interest to note the main centres in New Zealand have permanent installations, some of which are being extended. Also smaller boroughs and towns have modernised their street lighting systems, Whangarei having just ordered 15 lanterns in addition to 15 which have been in use for some few months. Two fittings installed use the same lamps as are in the present street lights but, due to special glassware surrounding the lamp, the light is directed down in a strip on to the road instead of being largely lost above the lamp. This principle of refraction of light or bending of light rays is similar to that used on car headlamps where the light is thrown in a flat beam ahead of the car. The discharge lamp fittings also use special glasses arranged to throw a beam in the direction of the traffic approximately 50 per cent, stronger than against oncoming traffic so as to eliminate any glare. The quality of the light also appears to show to best advantage when driving on a wet night when the ordinary or existing lights are very ineffective-