Enhanced Night Visibility Series, Volume IV: Phase II - Study 2: Visual Performance During Nighttime Driving in Rain

Phase II, Study 2 (rainy weather) was performed following the same procedures used for Study 1 (clear weather). Study 2 helped expand the knowledge of how current vision enhancement systems can affect detection and recognition of different types of objects while driving during adverse weather, specifically during rain conditions. The empirical testing for this study was performed on the Virginia Smart Road; the rain was controlled by weather making equipment. Thirty participants were involved in the study. A 12 by 7 by 3 mixed factorial design was used to investigate the effects of different types of vision enhancement systems, different types of objects on the roadway, and driver's age on detection and recognition distances; subjective evaluations also were obtained for the different vision enhancement systems. The results of the empirical testing suggest that vision enhancement systems that include halogen headlamps as their main component (i.e., halogen alone or halogen with ultraviolet A) consistently allow drivers the best detections during rain conditions. In fact, the halogen headlamp (low-beam configuration) provides the longest detection and recognition distances overall; in the few trials where other systems allow farther detection distances, these differences did not represent meaningful improvements. Even drivers using the infrared thermal imaging system, which resulted in farther detection distances for pedestrians and cyclists under clear conditions, perform no differently in the rain than when only the low beams of the vehicle were used.