The most frequent cause of motorcycle accidents involves another vehicle violating the motorcycle's right-of-way at an intersection. In addition to detection errors, the misperception of the approaching motorcycle's speed and time-to-arrival is another driver error that may account for these accidents (e.g., Horswill et al., 2005). This misperception has been shown to be related to the small size of the motorcycle and the small angular velocity when it is approaching. In two experiments we tested the impact of different motorcycle headlight configurations in various ambient lighting conditions (daytime, dusk and nighttime). The participants drove the driving simulator and had to turn left across a line of vehicles composed of motorcycles and cars. The motorcycles were equipped with either a "standard" front light, a "horizontal configuration" (additionally to the standard front light, two lights were appended on the rear view mirrors so as to visually increase the horizontal dimension of the motorcycle), a "vertical configuration" (one light on the rider helmet and two lights on the fork were added to the standard front light so as to increase the vertical dimension of the motorcycle), or a "combined" configuration (combining the horizontal and vertical configurations). The findings indicated that in nighttime conditions both the "vertical" and "combined" configurations significantly increased the gap car drivers accepted towards motorcycles when compared with the standard configuration, and that the accepted gaps did not significantly differ from those accepted towards cars. The advantage of the vertical and combined configurations showed up especially when the approach speed of the motorcycle was high. A similar pattern appeared in dusk conditions, whereas benefits were less pronounced in daytime conditions. Results will be discussed with respect to a possible applications on motorcycles.
