Enhanced Safety Prediction Methodology and Analysis Tool for Freeways and Interchanges

The U.S. freeway system is aging and becoming more congested; many parts of the freeway system, particularly interchanges, are in need of reconstruction or rehabilitation. Improved safety is a key justification for many interchange improvement projects, but engineers lack a suitable tool to examine the safety performance of existing interchanges and to anticipate the safety performance of new or rebuilt interchanges. A preliminary tool was developed by FHWA to estimate crash frequencies of typical interchanges of freeway and arterial, and freeway to freeway. The Interchange Safety Analysis Tool (ISAT) is a spreadsheet that consolidated crash prediction models and modification factors on most components of interchange systems in urban and rural areas. ISAT provides crash estimates of various typical interchange configurations over an economic life specified by users. This tool however requires significant enhancements to improve the quality of the underlying models, expand to key highway characteristics, and calibrate the models for some state data. The objective of this research is to develop additional and stronger crash prediction models for freeway and ramp elements, and to create new models for typical ramp terminal intersections and crash models for crossroad segments affected by these terminals. Another objective is to account for additional interchange characteristics or useful variables. And a final objective is to upgrade the interchange safety analysis tool (ISAT) spreadsheet to be more practical and user friendly and compatible with existing procedures. The following tasks are recommended: (1) determine major models and highway characteristics that should be improved and additional models that should be developed and useful variable to be considered; (2) acquire the data and conduct the analysis; (3) update the ISAT program; (4) select two states with adequate data to calibrate the ISAT program and calibrate the models to the selected states to be readily available for direct application; and (5) prepare a final report, and a user manual. This project will provide the much needed tool to create a more reliable interchange safety analysis tool that is very useful to engineers and planners in conjunction with environmental and traffic impact studies. </font></span></div>


  • English


  • Status: Completed
  • Funding: $700000.00
  • Contract Numbers:

    Project 17-45

  • Sponsor Organizations:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Niessner, Charles

  • Performing Organizations:

    Texas A&M Research Foundation, College Station

    Texas A&M University
    College Station, TX  United States  77843
  • Principal Investigators:

    Bonneson, James

  • Start Date: 20090511
  • Expected Completion Date: 0
  • Actual Completion Date: 20120831
  • Source Data: RiP Project 18039

Subject/Index Terms

Filing Info

  • Accession Number: 01462598
  • Record Type: Research project
  • Source Agency: National Cooperative Highway Research Program
  • Contract Numbers: Project 17-45
  • Files: TRB, RiP, USDOT
  • Created Date: Jan 3 2013 2:06PM