title: Frequency of extreme weather events and increased risk of motor vehicle collision in Maryland.
abstract: BACKGROUND
  Previous studies have shown increased precipitation to be associated with higher frequency of traffic collisions. However, data regarding how extreme weather events, projected to grow in frequency, intensity, and duration in response to a changing climate, might affect the risk of motor vehicle collisions is particularly limited. We investigated the association between frequency of extreme heat and precipitation events and risk of motor vehicle collision in Maryland between 2000 and 2012.
  
  
  METHODS
  Motor vehicle collision data was obtained from the Maryland Automated Accident Reporting System. Each observation in the data set corresponded to a unique collision event. This data was linked to extreme heat and precipitation events that were calculated using location and calendar day specific thresholds. A time-stratified case-crossover analysis was utilized to assess the association between exposure to extreme heat and precipitation events and risk of motor vehicle collision. Additional stratified analyses examined risk by road condition, season, and collisions involving only one vehicle.
  
  
  RESULTS
  Overall, there were over 1.28 million motor vehicle collisions recorded in Maryland between 2000 and 2012, of which 461,009 involved injuries or death. There was a 23% increase in risk of collision for every 1-day increase in extreme precipitation event (Odds Ratios (OR) 1.23, 95% Confidence Interval (CI): 1.22, 1.27). This risk was considerably higher for collisions on roads with a defect or obstruction (OR: 1.46, 95% CI: 1.40, 1.52) and those involving a single vehicle (OR: 1.41, 95% CI: 1.39, 1.43). Change in risk associated with extreme heat events was marginal at best.
  
  
  CONCLUSIONS
  Extreme precipitation events are associated with an increased risk of motor vehicle collisions in Maryland.
authors.affiliation: Environmental Health Bureau, Prevention and Health Promotion Administration, Maryland Department of Health and Mental Hygiene, Baltimore, MD, United States.
authors.forename: Ann
authors.initials: A
authors.lastname: Liu
authors.affiliation: Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, MD, United States.
authors.forename: Sutyajeet I
authors.initials: SI
authors.lastname: Soneja
authors.affiliation: Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, MD, United States.
authors.forename: Chengsheng
authors.initials: C
authors.lastname: Jiang
authors.affiliation: Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, MD, United States.
authors.forename: Chanjuan
authors.initials: C
authors.lastname: Huang
authors.affiliation: National Study Center for Trauma and EMS, University of Maryland Baltimore, Baltimore, MD, United States.
authors.forename: Timothy
authors.initials: T
authors.lastname: Kerns
authors.affiliation: Behavioral and Community Health, University of Maryland School of Public Health, College Park, MD, United States.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Beck
authors.affiliation: Environmental Health Bureau, Prevention and Health Promotion Administration, Maryland Department of Health and Mental Hygiene, Baltimore, MD, United States.
authors.forename: Clifford
authors.initials: C
authors.lastname: Mitchell
authors.affiliation: Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, MD, United States. Electronic address: amirsap@umd.edu.
authors.forename: Amir
authors.initials: A
authors.lastname: Sapkota
mesh_terms: D000063:Accidents, Traffic; D006801:Humans; D008396:Maryland; D018986:Motor Vehicles; D012306:Risk; D014887:Weather
keywords: Climate change; Collision; Extreme heat; Extreme precipitation; Injury; Motor vehicle accident