Investigating Impact of Sun Glare on Transportation Safety

Abstract

Effect of weather and environmental conditions on traffic operations and safety has always been very important transportation research topic since research findings indicate that adverse weather conditions influence traffic operational parameters and influence driver’s performance. To quantify the impact of adverse weather on traffic operations and safety the research community has focused primarily on adverse effects of rainfall and snowfall as these are fairly obvious causes of adverse weather, and data are also easier to obtain from weather stations to perform further analysis. While bright sunny days appear to be ideal for driving, discomforting sun glare could be equally detrimental to traffic safety and pose serious driving hazards. Motivated by the research findings from a study by Mitra, Washington and Van Schalkyk (2007), where sun glare was identified as an important omitted variable; this study is oriented towards investigating and analyzing the characteristics of glare related crashes. The task is performed by comparing and contrasting crashes that are supposed to be affected by morning and evening sun-glare with those that are unaffected by glare. To identify glare-related crashes, sun rise and sun set data are obtained from National Oceanic and Atmospheric Association (NOAA) and windows of worst possible glares are computed. Crashes occurred in east and west bound directions during morning and evening are tested to check if sun glare could be responsible for higher crash occurrences along those directions. The analyses are performed using statistical methods such as ANOVA and chi-square test for proportions. The trend and patterns of glare crashes and the outcomes of the statistical tests indicate that sun-glare indeed has strong influence on crash occurrence. There are also enough statistical evidences that shows the effects of glare are the worst in early spring and early fall and the least during summer. However, findings provided no compelling reasons to conclude that certain crash maneuvers as well as severities are highly elevated by sun glare; an important finding for accident reconstruction. Promising directions in which the findings could be applied and this study may be extended are also discussed.