Evaluating the Applicability of SSAM for Modeling the Safety of Roundabouts

The number of roundabouts in the United States continues to increase due in large part to the safety related benefits associated with the design. Safety remains an ongoing national priority, and roundabouts decrease crash rates and severity compared to other intersection designs including signalized intersections and stop sign controlled intersections. However, safety evaluation of transportation designs with the use of field data is not always feasible due to high costs and the fact that one cannot always evaluate alternative designs unless the changes are actually implemented. The Federal Highway Administration developed the Surrogate Safety Assessment Model (SSAM) that can read vehicle trajectory files obtained from micro-simulation models and estimate the number of conflicts based on several safety surrogate measures (i.e, measures that can be used as proxies to safety levels) including time to collision, post encroachment time (i.e., the time between when a vehicle last occupied a position and a second vehicle subsequently arrives at the same position), vehicle speed differential, and collision angle. The objective of this research was to evaluate the applicability for SSAM as a means for estimating the number of conflicts at a roundabout. As part of the analysis video data was collected and used to calibrate and validate a micro-simulation model integrating SSAM. Although the predicted and actual number of conflicts was low, the relative match of the predicted and observed models was encouraging, and provided evidence to suggest the appropriateness of using SSAM to model the safety of roundabouts.

• Supplemental Notes:
  • This paper was sponsored by TRB committee ANB75 Roundabouts.
• Corporate Authors:

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Roach, Derek
  • Christofa, Eleni
  • Knodler, Michael A
• Conference:
  • Transportation Research Board 94th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2015-1-11 to 2015-1-15
• Date: 2015

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 14p
• Monograph Title: TRB 94th Annual Meeting Compendium of Papers

Subject/Index Terms

• TRT Terms: Evaluation and assessment; Mathematical models; Roundabouts; Traffic safety
• Identifier Terms: Surrogate Safety Assessment Model
• Subject Areas: Highways; Safety and Human Factors; I73: Traffic Control; I82: Accidents and Transport Infrastructure;

Filing Info

• Accession Number: 01557392
• Record Type: Publication
• Report/Paper Numbers: 15-5207
• Files: TRIS, TRB, ATRI
• Created Date: Mar 20 2015 3:21PM