Auxiliary lighting to improve rear visibility of trucks and buses.

Research on the inadequacy of the rear signal lights of older vehicles, especially trucks, is reviewed. It is stated that tail-lights and reflectors should enable the driver following a vehicle to detect the presence, speed and location of a moving or stationary vehicle on the roadway at night at distances comparable with those possible during the day. Rear lighting should also convey to the following driver what the driver of the lead vehicle is doing or planning to do. Experimentation with a truck, having a 10- foot high closed end van with the upper half glossy white and the lower half glossy red, with a pair of 32 candle power auxiliary lamps mounted low to illuminate the outside of the rear doors is reported. Photographs taken from directly behind the truck at a distance of 100 feet showed that auxiliary lights improved the visibility of the truck as judged from all viewing distances and all conditions of highway lighting. A second experiment involved the use of an unpainted plywood panel, 8 foot by 8 foot, mounted vertically to simulate a truck rear end. Two tail-lights were mounted at several separations at 42 inches above the ground, two floodlights lighted the plywood pannel. A test car with a motor driven shutter to permit the driver to see the target for 3/4 of a second in a 3-second cycle, approached the target at a speed of 20 m.p.h. results indicate that with the tail-lights maximally separated (8 feet) and without floodlights, the average distance at which it could be determined correctly whether the truck was stopped was 477 feet, compared to 638 feet when fully lighted. With normally spaced tail-lights (only 3 feet apart) the results were 279 feet without flood, compared to 638 with. It is concluded that with only tail-light separation as a cue, it is more difficult to judge when a truck appears to be stopped. The closer the lights, the more dangerous they are to the following driver. It is recommended that floodlighting be employed to light the entire rear of trucks and buses in addition to present rear lighting. Research should be conducted to devise some system (such as directed air) to reduce the normal accumulation of dust, mud, snow, etc., on the rear lights with the goal to maintain peak efficiency. /SRIS/.