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9th August 1935, Page 32
9th August 1935
Page 32
Page 32, 9th August 1935 — Modern
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Street-lighting Methods

The Urgent Need for Improvement in the Illumination of Streets in Built-up Areas has Resulted in the Development of Many Efficient Systems

FOLLOWING upon the interest that was aroused earlier in the year in street lighting, during the Tramways, Light Railways and Transport Associations Conference, it is apropos to consider the progress that has been made in this respect. With the steadily?' increasing number of road users it becomes of urgent importance that the antiquated and obsolete methods of street lighting still in general use be replaced by more efficient systems. Insurance-company figures show that accidents on the roads are considerably higher during the hours of darkness and that the increase is almost entirely due to drivers and pedestrians not being

able to see clearly. • .

In the 17th century the road users of New York City were safeguarded from the often murderous dangers of the night by a law decreeing that every householder should place a lantern in his or her front window under penalty of a ninepenny fine for each night defaulted. To-day we have progressed • to the enviable state when some sort of street lighting is to be found throughout practically all built-up areas. Nevertheless, in many busy shopping throughfazes, the lighting is so inadequate, and dazzle from brilliantly lit shops, ill-directed street lamps and glassy road surfaces so confusing, that a state of total darkness might after all be preferable.

At last, however, serious steps are being taken to remedy the defects, and, within the past year or two, we have been introduced to systems which B26

are revolutionary in their improved light-giving power and general efficiency'. New methods of street illumination are being marketed by all the chief electrical concerns, such as the General Eleetric Co., Ltd., Siemens Ltd., the Edison Swan Electric Co., Ltd., and the British Thomson-Houston Co., Ltd., under the • pleasantly picturesque trade names of Osira, Sieray, Ecsura, Mazda Mercra and Mazda Sodra.

The basic principle in all cases is to combine a high-efficiency lamp with a carefully designed lamp-standard and reflector layout. The lamps, which have been evolved to satisfy present exacting requirements, belong to the electric-discharge type, of which the Neon tube is a familiar example. Actually, two main designs are at present engaged in friendly -rivalry for pride of place, but neither of them can boast much advantage over the other. The one, known as the mercury-vapour lamp, has gained much favour in this country, whilst the other, known as the sodium-vapour lamp, reigns supreme in America and on the Continent.

All mercury-vapour lamps give a characteristic greenish light which lacks the various red shades ; consequently, although the majority of colours look quite normal under such lighting, anything in which there is a predominating amount of red appears unnatural and somewhat ghoulish. At the moment experiments are being made to neutralize this colour effect, but So far any success hasbeen accompanied by an unwelcome drop in efficiency.

Sodium-vapour lamps, on the other hand, give a golden yellow light which is mono-chromatic, thus making all objects within its range of illumination appear as black or tinted yellow.

The correlation between lamps, lamp. standards and reflectors has given much food for research. In fact, now that the optical questions have been fully examined, and the fruits of experiment combined with the new types of lamp, it has been possible to effect an improvement in lighting efficiency of 200 per cent, over the normal tungstenfilament bulb, without any increase in current consumption or loss in useful life.

Latterly, attention has been drawn to a consideration of the suitability or otherwise of certain road surfaces, as regards their connection with street lighting. Opinion would seem to favour light-coloured roads with • a matt finish, such as concrete or tar impregnated with small stone chips. Under such conditions a sodium or mercury lamp can be made to work to its full advantage.

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Locations: New York City

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