Long-term trends in weather-related crash risks

This study explores whether automobile travel during inclement weather has become more or less risky over the past two decades. The analysis is based on the integration of two government databases and a matched-pair framework for comparing casualty rates under different weather conditions for 10 Canadian cities. The most notable result is a downward trend in relative risk during rainfall from 1984 to 2002 – both overall and when further disaggregated by injury severity combined with precipitation amount, city group, and time of day. By contrast, the overall relative risk of casualty during snowfall shows no significant change over time.