Frequency of Extreme Events and Injury Risk From Motor Vehicle Accidents in Maryland, USA

Abstract

Introduction: Several studies have shown associations between an increase in precipitation and a higher frequency of traffic accidents; a few have examined the relationship between high temperatures and motor vehicle crashes. However, to our knowledge, no studies exist assessing how extreme events, projected to grow in frequency, intensity, and duration in response to our changing climate, will impact the risk of injury from motor vehicle accidents. Our study quantified the association between frequency of extreme heat and precipitation events and change in injury risk from motor vehicle accident in Maryland between 2000 and 2012. Methods: Motor vehicle accident data was obtained from the Maryland Automated Accident Reporting System. Each observation in the data set corresponded to a unique collision event. A time-stratified case-crossover design was utilized to assess the association between exposure to extreme heat and precipitation events and risk of injury or death from motor vehicle accident. Additional stratified analyses examined risk by road type and season. Results: Over the study period, there were 461,009 motor vehicle accidents that resulted in injury or death. We observed an 18% increase (OR: 1.18; 95% CI: 1.17, 1.19) in risk of motor vehicle injury for every 1-day increase in extreme precipitation event, with the highest risk (29%) observed during autumn (OR: 1.29; 95% CI: 1.27, 1.32). Extreme precipitation related increase in motor vehicle injury was considerably higher when a road defect or obstruction was present (OR: 1.42, 95% CI: 1.32, 1.52). Changes in risk associated with extreme heat events were generally marginal. Conclusion: Extreme precipitation events, particularly in conjunction with a road defect or obstruction, are associated with an increased risk of injury from motor vehicle accidents in Maryland. Our results suggest that projected increases in frequency of extreme precipitation event will have a significant impact on public health.