Fast-Rise Brake Lamp as a Collision-Prevention Device

摘要

Conventional tungsten-filament brake lamps have a relatively slow rise time. Ittakes approximately 250 msec for them to reach 90 percent of the asymptotic luminous intensity. The slowness of response can cause important delays of warning information to following drivers. The authors have designed a simple and relatively inexpensive circuit that produces a faster warning signal using a conventional lamp. As the authors have reported previously, the device reduces reaction times to the onset of brake lamps by about 115 msec. The present study evaluated the benefits of a 115 msec reduction in driver brake reaction time. Two approaches were used. In the first approach the authors calculated the reductions in effective stopping distance assuming a range of initial speeds. The results indicate, for example, that if the initial speed is 100 km/h, the reduction in the effective stopping distance is 3.2 m. In the second approach the authors calculated the reductions in the proportions of very long reaction times, assuming a normal distribution of reaction times that is shifted by 115 msec. For the distribution without the device the authors assumed a mean of 1.25 sec and a standard deviation of 0.46 sec. The results indicate, for example, that decreasing the mean by 115 msec yields a 55 percent reduction in the frequency of reaction times that are longer than 2.5 sec.