RES2020-04: A Localized Safety Performance Functions (SPFs) Approach Accounting for “Within” Tennessee Variations on Freeways & Interchanges

The Tennessee Department of Transportation (TDOT) is adopting the Highway Safety Manual (HSM) as a resource to assess the safety performance on Tennessee (TN) roadways. The HSM (2010) provides Safety Performance Functions (SPFs) to predict crash frequency on several types of roadway facilities, e.g., segments and intersections. HSM recommends that transportation agencies develop either their own jurisdiction-specific SPFs or calibrate the default HSM SPFs using local data. The rationale behind this is that the HSM SPFs were developed using data from a few states in the U.S., which may not be representative of other states due to potential variability in conditions. To assist with implementing HSM procedures, the University of Tennessee has worked closely with TDOT to develop TN-specific SPFs for various types of rural and urban roadway segments in Phases I and II of the project. This phase (III) relates to SPFs for freeway segments and interchange ramps in Tennessee. The study 1) develops calibration factors (CFs) for freeway segments (interstates and expressways) and interchange ramps, 2) estimates TN-specific SPFs for freeway segments and interchange ramps, and 3) provides “highly localized” SPFs for freeways. A unique aspect of this study is dealing with heterogeneity by investigating the spatial and temporal variations in crash frequencies and associated factors using statistical models, known as geographically and temporally weighted regressions. The results reported in this study are ready for implementation by TDOT, e.g., by using crash prediction tools supplied as part of this project. The report also lists recommendations for enhancing safety analysis in TN.

Language

  • English

Project

  • Status: Completed
  • Funding: $174966
  • Contract Numbers:

    RES2020-04

    40100-07219

    60676

  • Sponsor Organizations:

    Tennessee Department of Transportation

    James K. Polk Building
    Fifth and Deaderick Street
    Nashville, TN  United States  37243-0349
  • Managing Organizations:

    Tennessee Department of Transportation

    James K. Polk Building
    Fifth and Deaderick Street
    Nashville, TN  United States  37243-0349
  • Project Managers:

    Jonas-Fields, Stephanie

  • Performing Organizations:

    University of Tennessee, Knoxville

    Center for Transportation Research
    Conference Center Building
    Knoxville, TN  United States  37996-4133
  • Principal Investigators:

    Khattak, Asad

  • Start Date: 20191101
  • Expected Completion Date: 20220228
  • Actual Completion Date: 0
  • USDOT Program: Transportation, Planning, Research, and Development

Subject/Index Terms

Filing Info

  • Accession Number: 01744115
  • Record Type: Research project
  • Source Agency: Tennessee Department of Transportation
  • Contract Numbers: RES2020-04, 40100-07219, 60676
  • Files: RIP, STATEDOT
  • Created Date: Jun 25 2020 5:52PM