Effects of Sequential Turn Signals under Realistic Visual Conditions

Sequential turn signals are becoming more common, partly because of the availability of the detailed temporal and spatial control of light that is allowed by LED sources. They seem to be popular with drivers, and some human factors considerations suggest that they may more effectively convey information about intended maneuvers. This research was designed to investigate possible benefits by presenting experimental participants with a variety of sequential and static turn signals under realistic field conditions. The experimental tasks were based on possible encounters at four-way intersections. Passenger cars were statically positioned to represent such encounters. Participants were seated in one of the vehicles and were asked to make simple but meaningful judgments about intended turns by the other vehicles. Visual conditions were realistic in terms of the viewing geometry and photometry. Experiments were conducted in the day and at night. Three experiments were performed. In two of the three experiments there were statistically significant preferences for sequential turn signals over static turn signals in subjective ratings, but comparisons between sequential and static turn signals in objective measures were not statistically significant in any of the three experiments.