Risk of Motor Vehicle Crash, Injury, and Death Associated with Severe Weather in Arizona, USA

Motor vehicle crashes are a leading cause of injury and death. While adverse weather is reported for a large number of motor vehicle fatalities for the USA, the type of adverse weather and the rate of associated fatality vary geographically. Severe dust storms, often causing severe multiple vehicle accidents, are one of the primary meteorological phenomena of concern for motorists during the monsoon season in Arizona, USA. We analyzed Arizona Department of Transportation crash incident data that contains all motor vehicle accidents in Arizona from 2011 to 2015. The dataset includes information about location of the crash, time, date, and weather conditions. In this presentation, we will discuss temporal and spatial variation in the fatality rates across Arizona’s counties. We will also describe the risk of fatality during car crashes associated with different severe weather categories relative to clear sky conditions as estimated by Poisson regression.

Considering only those cases with known weather conditions during the car crash, fog/smoke and dust were two severe weather conditions with highest risk of fatality from car crash relative to clear sky. The risk of fatality under dust storm conditions was 1.7 times higher than during clear skies and 2.2 times higher than during rain. However, car crashes with the unknown weather conditions were those with the absolutely highest fatality risk. These accidents were mostly associated with night conditions, while highest rate of the unknown-weather related fatalities was observed in the northeast portion of the state. These results may help to local authorities and police departments addressed and potentially prevent excess fatalities during inclement weather in their counties.