Abstract
Thirty subjects, in two age groups, were instructed to respond as quickly and acurrately as possible to different combinations of lights presented on the rear of a model automobile. The combinations simulated normal as well as malfunction signal conditions. Turn signals, which were either red or amber, were presented at one of two light intensities, each corresponding to intensities currently required on the road. Selected stimuli were viewed separately against two extreme conditions of ambient illumination. In addition, brake lights were alternately combined with low-intensity presence lights under one lens.