Identification of Potentially Hazardous Roadway Network Locations Using Microscopic Observational Vehicle Data and Macroscopically Modeled Reaction Time

The car following model developed by Gazis, Herman, and Rothery (known as the GHR model) can yield an analytical estimate of driver reaction time required for asymptotic stability as a function of density. Furthermore, equivalent steady-state macroscopic flow models have been derived for this car-following model. This study exploits this bridge between the macroscopic and microscopic version of the GHR model and hypothesizes that this reaction time and its change with the change of traffic state will demonstrate a correlation with observed crash rates that can be exploited in the USDOT’s Highway Safety Manual methodology, thereby providing improved estimation of road segment safety performance. One of the challenges to investigate this hypothesis is to identify the transition state and to determine the change in reaction time during this state. To tackle this issue, the format of the GHR model developed in this study is characterized by the discontinuous traffic flow model. It enables the modeling of two traffic states for the density region where the traffic stream may be either in an uncongested or congested state and may transition from one regime to the other. When the driver reaction time required for asymptotic stability is estimated for the two regimes, the discontinuous model also reveals the drop in driver reaction time during transition. The primary objective of this study is to investigate the relationship between freeway crash rates and this drop in driver reaction time during transition of traffic states.

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  • Summary URL:
  • Supplemental Notes:
    • This document was sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
  • Corporate Authors:

    National Transportation Center at Maryland

    1124 Glenn Martin Hall
    University of Maryland
    College Park, MD  United States  20742

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Authors:
    • Ahmed, Ishtiak
    • Williams, Billy M
  • Publication Date: 2018-3


  • English

Media Info

  • Media Type: Web
  • Edition: Final Report
  • Features: Appendices; Figures; References; Tables;
  • Pagination: 49p

Subject/Index Terms

Filing Info

  • Accession Number: 01666577
  • Record Type: Publication
  • Report/Paper Numbers: Project ID: NTC2015-MU-R-07
  • Created Date: Apr 2 2018 10:43AM