Well-lit Roads =Non-skid Surfaces
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T HERE was a common factor in both .1 an efficiently illuminated roadway and a non-skid surface. Dr. W. H. Glanville, director of the Road Research Laboratory, made this point when he delivered his paper, "Light and road safety," to the Illuminating Engineering Society in London last week.
It was explained that the old finetextured road surface of smooth compressed asphalt produced a surface that gave rise to more skidding and was not conducive to safe illumination.
This was even more apparent when the surface was wet, for flooding of the road, because of the fine nature of the compressed asphalt. produced a deceptive and streaky lighting effect.
The medium-grade surface, obtained by the use of modern rolled asphalt was far more satisfactory. Tests at the Laboratory bad been made with a photometer to measure the preferential reflection of road surfaces. Tests were also conducted with an adapted car, incorporating a fifth wheel mounted in an offset position.
This apparatus measured the amount B32 of sideways co-efficient and had proved that the medium-grade surface was less prone to produce skidding. This also reduced flooding, gave rubber tyres less opportunity to scuff, and thereby polish the surface, and gave the most acceptable medium for safer street illumination.
It was claimed that the benefits of lighting modernization were fully justified on a purely economic ground. Even when the humanitarian factor of the reduced number of injuries was temporarily forgotten, statistics collected from 64 selected sites showed that modernization schemes paid for themselves.
Figures showed that whilst the number of accidents during daylight rose by 14 per cent., at night on the same stretches of road subjected to modern lighting techniques the accident rate had declined by 20 per cent.
"How to eliminate dazzle and still see" was how Dr. Glanville summarized the problem of vehicle lighting. He stated that headlight systems were among the most neglected items of equipment on vehicles in this country.
Reference was made to the AngloAmerican. the European and the latest unified European beams. Various tests at the Laboratory had shown that 90 per cent. of drivers preferred to drive behind a white beam rather than a yellow, even if they preferred to meet a yellow light.
Experts considered that visibility was equally good using the white AngloAmerican beam or the yellow European beam, bearing in mind the different mainbeam dipping techniques of the two systems.
Polarized lighting systems and vehicle glazing presented far greater problems, observed Dr. Glanville. He quoted the result of experiments conducted in the ' U.S.A. where, he said, it had been estimated that the introduction of a polarized system would add £100 to vehicle cost.
The suggestion had been made, he said, that if new vehicles were fitted with a polarized system, pure economics would prevent full benefit being received by all for at least seven years. in the interim it was obvious that variations from a polarized standard would he dangerous.