A comparisons of visibility and readability between reflectorized and conventional licence plates has been made under different conditions of darkness as well as in daylight. Two shapes of plates were investigated: rectangular (10x45 cm) and near-square (20x25 cm). The conventional plates were white and the reflective silver, yellows and red. The symbols were in all cases black and of Swedish standard size. The measured distances were obtained by observers in a moving car reporting when they detected, or could read, the test plates. The result can be summarised as follows: 1) There was no difference under any conditions between rectangular and square plates. 2) In daylight, the same reading distance was obtained (approx 40 m) for both types of plates. 3) At night the reflectorized plates gave longer both reading and detection distances when the observation car used its headlights. a. When the "testplate"car showed no lights, reflectives plates were readable from twice the distance (approx. 35 m) of conventional plates. b. When the test plate was located between two lit headlights, the reading distance for reflectorized plates was three times longer (approx. 35 m) than for conventional plates. c. The detection distance for reflective plates was approximately six times (115 m) that of conventional plates when the test-plate car used only a single headlight. 4) When the test-plate car showed no lights, the reflective plates gave five times the detection distance (approx. 250 m) of conventional plates.
Abstract