Highway Safety Manual Safety Performance Functions & Roadway Calibration Factors: Roadway Segments

To enhance safety, the Tennessee Department of Transportation (TDOT) is in the process of adopting the Highway Safety Manual (HSM) as a resource to facilitate decision making based on the safety performance of its roadways. The predictive models which are known as Safety Performance Functions (SPFs) are used to forecast the expected crash frequency for various roadway facility types. The HSM (2010) recommends transportation agencies such as TDOT either to develop their own SPFs using local data or develop calibration factors for use with the HSM default SPFs to reflect local conditions. This is because the HSM default SPFs were developed using data from a subset of states. Geographical conditions in Tennessee may differ substantially from the factors used to develop the default SPFs in the HSM such as terrain, weather, animal populations, driver populations, crash reporting thresholds, and crash reporting practices. Therefore, this study undertakes the task of developing 1) Tennessee-specific calibration factors, and 2) estimating Tennessee-specific SPFs. The calibration factors and locally estimated SPFs presented in this report are ready for implementation in Tennessee. Part 1 of the report focuses on rural multilane segments and urban/suburban arterial segments (Part 2 focuses on relevant intersections). Given the availability of relevant data in E-TRIMS, TDOT is in a good position to adopt the HSM procedures and benefit from software applications that make it easier to use the HSM. In this regard, the AASHTO Safety Analyst tool is discussed in detail. An example demonstrates how the Safety Analyst can use calibration factors and locally calibrated SPFs to make predictions of crashes with and without countermeasures. At the end of the report, recommendations are provided for advancing safety analysis in Tennessee.

• Record URL:
  https://www.tn.gov/content/dam/tn/tdot/long-range-planning/research/final-reports/res2016-final-reports/Final%20Report_RES2016-27%20Part%201%20Phase%20II_TDOT.pdf
• 
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/55069
• Corporate Authors:

  University of Tennessee, Knoxville

  Center for Transportation Research
  Conference Center Building
  Knoxville, TN  United States  37996-4133

  Tennessee Department of Transportation

  Statewide Planning and Research Work Program
  James K. Polk Buidling, Suite 909, 505 Deaderick Street
  Nashville, TN  United States  37243

  Tennessee Department of Transportation

  505 Deaderick Street
  Nashville, TN  United States  37219-0334

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Khattak, Asad
  • Ahmad, Numan
  • Mohammadnazar, Amin
  • Mahdinia, Iman
  • Wali, Behram
  • Arvin, Ramin
• Publication Date: 2020-6

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Appendices; Figures; References; Tables;
• Pagination: 116p

Subject/Index Terms

• TRT Terms: Calibration; Crash risk forecasting; Predictive models; Safety analysis
• Identifier Terms: Highway Safety Manual; Tennessee Department of Transportation
• Geographic Terms: Tennessee
• Subject Areas: Highways; Planning and Forecasting; Safety and Human Factors;

Filing Info

• Accession Number: 01772154
• Record Type: Publication
• Report/Paper Numbers: RES 2016-27
• Files: NTL, TRIS, ATRI, USDOT, STATEDOT
• Created Date: May 21 2021 10:57AM