An Improved Braking Indicator

Conventional brake lights require 250 msec to reach 90% intensity, thereby causing potentially important delays of warning information to following drivers. Several improvements are possible, including the use of LED displays. LED's, however, are more expensive than conventional incandescent bulbs and require redesign of lamp housings. As an alternative, we have designed a simple and relatively inexpensive circuit that produces a faster warning signal using a conventional bulb. We have evaluated the benefits of this device in a laboratory study that measured subjects' reaction times to the onset of brake lights in a simulated car-following situation. Our data indicate that the benefit of the device is on the order of 115 msec. For a vehicle traveling at 65 miles per hour, that benefit translates to a decrease in stopping distance of 11 feet.