Sun glare and road safety: An empirical investigation of intersection crashes

Abstract

There is considerable research on adverse weather events such as fog, rainfall and snowfall on traffic operations and safety, since these environmental conditions either affect visibility or degrade pavement friction—thereby affecting safety and operations of traffic movement. Although bright sunny days appear to be ideal for driving, sun glare could be detrimental to traffic safety and pose serious driving hazards.With data from signalized intersections of Tucson, Arizona, an empirical investigation is performed here to assess how sun glare affects intersection safety. The task is performed by comparing and contrasting crashes that are possibly affected by morning and evening sun-glare with those that are unaffected by glare. Sun rise and sun set data, obtained from National Oceanic and Atmospheric Association (NOAA) is used and windows of worst possible glare are computed. Crashes along the east bound directions in the morning and those along the west during the evening glare window are tested to check if sun glare possibly influences crash occurrence. Analysis of the trends and patterns of glare crashes and the outcome of the statistical tests show some evidence that sun glare affects intersection crash occurrence. Results indicate that odds of glare crash occurrence are higher in east and west bound compared to north and south bound directions. Adverse effect of glare is found to be greater in early spring, fall and in winter compared to summer months. There is some evidence that rear-end and angle crashes at signalized intersections are affected by sun glare.