INDIRECT METHODS TO ACCOUNT FOR EXPOSURE IN HIGHWAY SAFETY STUDIES

One of the more complex issues in highway safety evaluation is how to incorporate some measure of exposure, some numerical measure of the opportunity for an accident to occur in the analysis. On a roadway section, for example, exposure might be vehicle-miles traveled (VMT). At fixed points, such as intersections, exposure might be some function of the annual average daily traffic (AADT) of the intersecting roads. However, the appropriate measure of exposure may not be at all clear, such as in driver- or vehicle-based analyses. In assessing the involvement of older drivers in left-turn accidents, for example, how does one measure the exposure of drivers by age at a specific site? Because of the difficulty of obtaining numerical exposure estimates, indirect methods have evolved for treating the exposure issue in a surrogate manner. This report is intended to be an instructional text on these methods for use by the highway safety research community. The indirect methodologies presented here include before/after evaluation designs, case-control studies, and the induced-exposure methodologies. The numerical computations for each methodology are presented in simple, step-by-step formulas, followed by a numerical example. A discussion of both the advantages and disadvantages and appropriate and inappropriate applications are also presented. It is hoped that this report will serve as a comprehensive guide for the highway safety researcher, both in designing and in evaluating highway safety studies.

• Record URL:
  • https://rosap.ntl.bts.gov/view/dot/68082
• Corporate Authors:

  Texas Transportation Institute

  Texas A&M University System, 1600 E Lamar Boulevard
  Arlington, TX  United States  76011

  Federal Highway Administration

  Turner-Fairbank Highway Research Center, 6300 Georgetown Pike
  McLean, VA  United States  22101
• Authors:
  • Pendleton, O J
• Publication Date: 1996-11

Language

• English

Media Info

• Media Type: Digital/other
• Features: Appendices; Figures; References; Tables;
• Pagination: 71 p.

Subject/Index Terms

• TRT Terms: Before and after studies; Case studies; Crash exposure; Estimates; Highway safety
• Uncontrolled Terms: Exposure
• Old TRIS Terms: Indirect methods; Induced exposure methodologies
• Subject Areas: Highways; Safety and Human Factors; I81: Accident Statistics;

Filing Info

• Accession Number: 00735918
• Record Type: Publication
• Report/Paper Numbers: FHWA-RD-96-141, Final Report, HS-042 464
• Contract Numbers: DTFH61-93-R-00123
• Files: HSL, NTL, TRIS, ATRI, USDOT
• Created Date: Apr 1 1997 12:00AM