Methods to Define Homogeneous Segments and Assign Crashes for Highway Safety Manual Applications

The AASHTO Highway Safety Manual (HSM) presents a variety of methods for quantitatively estimating crash frequency. The HSM predictive methods require the roadway network to be divided into homogeneous segments and intersections. The characteristics used to specify homogeneity vary depending on facility type, and could include number of lanes, shoulder width, traffic volume, median type, and a host of other characteristics. Despite the complexity and potential impacts of segmentation, there is a dearth of detail in documented procedures to determine homogeneous segment termini. To fill this void, this paper focuses on automation methods to determine appropriate roadway homogeneous segment termini for different facility types discussed in the HSM. Methods include a Microsoft Excel spreadsheet method using Visual Basic to subdivide roadway segments into homogeneous segments as well as an application for GIS platforms using multi-criteria dynamic segmentation. Both methods have been applied in support of an extensive HSM calibration project for South Carolina Department of Transportation. The paper also includes a case study using an actual roadway segment from South Carolina to demonstrate how the proposed spreadsheet procedure can identify appropriate homogeneous segments. The benefits of using these automated methodologies are summarized and recommendations for future research are discussed.

• Supplemental Notes:
  • This paper was sponsored by TRB committee ANB20 Standing Committee on Safety Data, Analysis and Evaluation.
• Authors:
  • Ogle, Jennifer Harper
  • Alluri, Priyanka
  • Zhang, Chi
  • Rajabi, Mahdi
  • Sarasua, Wayne
  • Bendigeri, Vijay
• Conference:
  • Transportation Research Board 97th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2018-1-7 to 2018-1-11
• Date: 2018

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 9p

Subject/Index Terms

• TRT Terms: Classification; Crash characteristics; Crash rates; Geometric segments; Mathematical prediction
• Identifier Terms: Highway Safety Manual
• Geographic Terms: South Carolina
• Subject Areas: Data and Information Technology; Highways; Safety and Human Factors;

Filing Info

• Accession Number: 01661268
• Record Type: Publication
• Report/Paper Numbers: 18-03826
• Files: TRIS, TRB, ATRI
• Created Date: Feb 26 2018 1:44PM