| Abstract | One factor needed to measure the effectiveness of automobile headlights, now being investigated in an NRC/MOT programme, is the distance required by a driver to stop his vehicle once an obstacle has been observed in the road ahead. This distance is primarily a function of the speed at which the vehicle is moving at the time the braking commences, but there are many other variables involved as well, the condition of the road surface and of the vehicle brakes and tires, the weather, and the skill of the driver, for example. However, by splitting up the problem into four separate cases, namely driving at night with or without the opposing glare of a car approaching in the left lane, each combined with wet or dry, pavement conditions, it is possible to make conservative estimates of stopping distance versus initial velocity for each of these cases. Thus it should be possible, given the headlight performance available in, for example, the car-meeting situation on a dry level road, to assign a maximum recommended speed suitable and safe for this particular case. The recommended maximum speed chosen should be such that most of the possible combinations of the other variables are covered, without being too restrictive in the majority of cases.
It is generally believed, and the figures of this report do nothing to dispell such a belief, that many vehicle operators "overdrive" their headlights. Judged by the results of previous work on headlights (for example Ref.1 & 9 ) there is certainly a need for improvement in automobile lighting systems. |
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