Driving risk under inclement weather has been long considered higher thanthat under normal weather conditions. Among several weather variables, rainfall is recognized as a critical one that affects traffic crash occurrences. Heavy rainfall often results in reduced visibility, increased stopping distances, hydroplaning and loss of control on the vehicle. Lack of quantitative, accurate representation of rainfall effects had been a problem in the past highway safety research on adverse weather. This study usedradar rainfall data from the National Weather Service WSR-88D NEXRAD Doppler Radar system that have superior properties in terms of: large spatial coverage over highway network, high spatial resolution (in the order of few kilometers), and continuous temporal sampling to quantify the relative crash risk with matched-pair method. Four different types of highways were selected for analysis on a four-year time period. The results on all four highways indicate a higher crash risk and a higher crash injury risk during rainy weather. The magnitude of the risk varies by type of highway, location of the highway, time of the day, crash severity, and crash characteristics. The knowledge gained by this study can help identify effective crash countermeasures.
Samenvatting