Article Text

Download PDFPDF
Explaining regional disparities in traffic mortality by decomposing conditional probabilities
  1. Gregory P Goldstein1,
  2. David E Clark1,2,
  3. Lori L Travis1,
  4. Amy E Haskins1
  1. 1Center for Outcomes Research and Evaluation, Maine Medical Center, Portland, Maine, USA
  2. 2Department of Surgery, Maine Medical Center, Portland, Maine, USA
  1. Correspondence to Dr David E Clark, Maine Medical Center, 887 Congress Street, Portland, ME 04102, USA; clarkd{at}


Background In the USA, the mortality rate from traffic injury is higher in rural and in southern regions, for reasons that are not well understood.

Methods For 1754 (56%) of the 3142 US counties, we obtained data allowing for separation of the deaths/population rate into deaths/injury, injuries/crash, crashes/exposure and exposure/population, with exposure measured as vehicle miles travelled. A ‘decomposition method’ proposed by Li and Baker was extended to study how the contributions of these components were affected by three measures of rural location, as well as southern location.

Results The method of Li and Baker extended without difficulty to include non-binary effects and multiple exposures. Deaths/injury was by far the most important determinant in the county-to-county variation in deaths/population, and accounted for the greatest portion of the rural/urban disparity. After controlling for the rural effect, injuries/crash accounted for most of the southern/northern disparity.

Conclusions The increased mortality rate from traffic injury in rural areas can be attributed to the increased probability of death given that a person has been injured, possibly due to challenges faced by emergency medical response systems. In southern areas, there is an increased probability of injury given that a person has crashed, possibly due to differences in vehicle, road, or driving conditions.

  • Decomposition
  • methods
  • models
  • mortality
  • MVC
  • public health
  • rural
  • south
  • traffic

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Funding This study was funded in part by US National Institutes of Health award R21HD061318.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the Maine Medical Center Institutional Review Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.