title: Effects of snowfalls on motor vehicle collisions, injuries, and fatalities.
abstract: OBJECTIVE
  We estimated the effects of snowfalls on US traffic crash rates between 1975 and 2000.
  
  
  METHODS
  We linked all recorded fatal crashes (1.4 million) for the 48 contiguous states from 1975 through 2000 to daily state weather data. For a subsample including 17 states during the 1990s, we also linked all recorded property-damage-only crashes (22.9 million) and nonfatal-injury crashes (13.5 million) to daily weather data. Employing negative binomial regressions, we investigated the effects of snowfall on crash counts. Fixed effects and other controls were included to address potential confounders.
  
  
  RESULTS
  Snow days had fewer fatal crashes than dry days (incidence rate ratio [IRR] = 0.93; 95% confidence interval [CI] = 0.90, 0.97), but more nonfatal-injury crashes (IRR = 1.23; 95% CI = 1.18, 1.29) and property-damage-only crashes (IRR=1.45; 95% CI=1.38, 1.52). The first snowy day of the year was substantially more dangerous than other snow days in terms of fatalities (IRR = 1.14; 95% CI=1.08, 1.21), particularly for elderly drivers (IRR=1.34; 95% CI=1.23, 1.50).
  
  
  CONCLUSIONS
  The toll of snow-related crashes is substantial. Our results may help estimate the potential benefits of safety innovations currently proposed by meteorology and traffic safety experts.
authors.affiliation: Department of Health Management and Policy, School of Public Health, University of Michigan, M3517 SPH II, Ann Arbor, MI 48109-2029, USA. daneis@umich.edu
authors.forename: Daniel
authors.initials: D
authors.lastname: Eisenberg
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Warner
mesh_terms: D000063:Accidents, Traffic / Q000401:mortality / Q000706:statistics & numerical data*; D000328:Adult; D000368:Aged; D006801:Humans; D008875:Middle Aged; D016012:Poisson Distribution; D012914:Snow; D014481:United States