INVESTIGATING CLIMATE IMPACTS ON WEATHER-RELATED CRASHES

Abstract

Adverse weather conditions due to precipitation are known to increase crash occurrence and fatality rates. One fifth of all vehicle crashes in the United States are weather-related, with a sixth of this value resulting in a fatality. However, the impacts vary by precipitation type and region. Weather regimes, which identify large-scale atmospheric patterns, are useful to study for accounting region-specific precipitation variability. This study examined the relationship between fatal weather-related crashes and ENSO-precipitation-anomaly and weather-related crashes and regime-precipitation-anomaly time scales to better understand subseasonal-to-seasonal variability in weather impacts to surface transportation and safety communication. Fatal crash, precipitation, snow, and weather regime data were combined to determine how strong climate impacts are to roads. Two important takeaways from this study are that: (1) the precipitation anomalies and fatal crash relationship is driven by anomalous liquid precipitation rather than anomalous snow or frozen precipitation and (2) weather regimes impact fatal weather-related crashes differently from region to region. Traffic safety has improved over time in terms of safety, though climate change may alter future trends. El Niño-Southern Oscillation (ENSO) patterns influence precipitation in some regions, which can affect crash rates, though direct links remain uncertain. Many fatal crashes occur without any prior warnings, indicating a need for improved safety communication to drivers about the dangers of adverse weather. Since climatology and driver behavior differ regionally, crash counts vary. Limitations include the lack of availability of earlier frozen precipitation data and non-fatal weather-related crash data.