Improving the Light From Vehicle Lamps
Page 14
If you've noticed an error in this article please click here to report it so we can fix it.
THE announcement was made last week that a new Order concerning the lighting on motor vehicles is to be issued by the Ministry of Home• Security making it legal to utilize simultaneously two head lamps, provided that these be properly masked. From September 13 permission to employ those and brighter tail lamps is accorded.
Until now only public-service vehicles have been permitted to have two head lamps in operation, but with both in action the intensity of illumination on a vertical surface placed at any point 10 ft. from either lamp must not exceed 2.5 ft. candles.
As the result of this Order all road users will be able to enjoy the same privilege, but it would seem that a similarly powered lamp to that more generally employed with the single mask, i.e., 36 watts, is permitted.
Commercial-vehicle drivers will view this curcession with mixed feelings. They will certainly appreciate the benefit to themselves in respect of their own vehicles, but already there have been complaints as to certain forms of mask utilized exclusively on private cars and on some commercial models, despite the fact that these forms are quite legal.
It must be remembered that however well designed a mask may be, it is most important that it should be accurately fitted, otherwise it may cause dazzle. In any event, a certain amount of dazzle effect must occur to other users of the road when a vehicle is approaching the crest of an acclivity, which must throw the beam above the level of the lamp in respect of the road beyond the crest. It is oply on the perfectly flat road that the fall benefits of masking can be derived.
We have not yet any direct information as to the new regulations, but it appears that, as at wesent framed, they will permit each lamp to give a maximum illumination of 2.5 ft. candles at a distance of 10 ft. from the lamp. Now, fhb interesting point occurs—and this is ti matter which ,we have raised with the Ministry of War Transport—as to whether or not the combined illumination ma), exceed the previous maximum value. If so this may introduce some complications. Certain forms of mask are so arranged that the illumination is more or less concentrated towards the front, whilst others, of more careful design, have devised means by which the mask will provide a more regular fan of light, that towards the sides being of little less value than the maximum permitted. Say that this side-ray value be 1.8 ft. candles, then, with the converging of two side beams, the total may possibly be about 3.6 ft. candles.
We have not made experiments in this direction, , and it is possible that the merging of the two powers would not be twice as great as the one at the regulation distance of 10 ft., although it might increase 'the illumination a little farther forward of this point. In such cases will the police take action after checking by the specially devised photometer, 'or, in the event of the total light' at any point 10 ft. from the lamp exceeding the present limit, will this slight extra light be permitted? No doubt means for overcoming the trouble could be devised, such as the dimming of the diffuser discs at their inner sides so as to limit the combined power where this proves necessary. It would probably be sufficient if, only one of the diffusers were to be treated in this manner, and this would avoid-any risk of introducing a poorly lighted lane in the path of the vehicle. Control. of the diffuser would obviate the difficulty of obtaining a huge number of lower-wattage lamps, which, incidentally, might not be available.
So far as tail lamps are concerned, we are quite certain that the present excessively dimmed lamps have been the cause of a considerable number of accidents—the result of overtaking by vehicles or collisions wish those parked on the road. The danger is particularly apparent on very dark nights and when there is mist.