U.S. Department of Transportation
Federal Highway Administration
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Washington, DC 20590
202-366-4000
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
 |
| Publication Number: FHWA-HRT-21-053 Date: May 2021 |
Publication Number: FHWA-HRT-21-053 Date: May 2021 |
PDF Version (1.28 MB)
Technical Report Documentation Page
| 1. Report No.
FHWA-HRT-21-053 |
2. Government Accession No. | 3 Recipient's Catalog No. | ||
| 4. Title and Subtitle
Developing Crash Modification Factors for Variable Speed Limits |
5. Report Date
May 2021 |
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| 6. Performing Organization Code | ||||
| 7. Author(s)
Raul Avelar (ORCID: 0000-0002-3962-1758), Eun Sug Park (ORCID: 0000-0001-6224-7007), Sruthi Ashraf (ORCID: 0000-0002-3304-9682), Karen Dixon (ORCID: 0000-0002-8431-9304), Minh Li (ORCID: 0000-0003-0129-1615), and Bahar Dadashova (ORCID: 0000-0002-4592-9118) |
8. Performing Organization Report No. | |||
| 9. Performing Organization Name and Address
Texas A&M Transportation Institute |
10. Work Unit No. (TRAIS) | |||
| 11. Contract or Grant No.
DTFH6116D00039-0002 |
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| 12. Sponsoring Agency Name and Address
Office of Safety Research and Development |
13. Type of Report and Period Covered
Final Report, May 2017–December 2020 |
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| 14. Sponsoring Agency Code
HRDS-20 |
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| 15. Supplementary Notes
The Federal Highway Administration Development of Crash Modification Factors Program and Task Manager for this project was Roya Amjadi (HRDS-20; ORCID: 0000-0001-7672-8485). |
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| 16. Abstract
The objective of this study was to perform rigorous safety effectiveness evaluations of variable speed limit (VSL) implementation on freeway corridors. To accomplish this objective, the research team compiled safety data from Virginia, Wyoming, and Georgia and used an interrupted time series study design (with a comparison group for Georgia). The team analyzed data using logistic and negative binomial generalized estimating equations models. The results from Wyoming and Georgia produced evidence of significant reductions in several types of crashes. The research team found total crash reductions of 34.4 and 29.2 percent associated with VSL installations in Wyoming and Georgia, respectively. The economic evaluation for these two States generally indicated larger benefits than costs. For Georgia, the estimated benefit–cost (B/C) ratio was 40.38. The economic analysis for Wyoming yielded a more modest B/C ratio of 9.05, though still indicating benefits outweighing VSL installation costs. Results from Virginia were inconclusive as the analysis found no statistical evidence of a change in overall safety. The inconclusiveness of these results is possibly due to the sample size of the after period, the small amount of time the system was active, and the manner in which the VSL was used in the corridor for enhancing safety during adverse weather conditions. |
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| 17. Key Words
Variable speed limit, VSL, dynamic speed limit, safety, crash modification factor, CMF |
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161. |
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| 19. Security Classification (of this report) Unclassified |
20. Security Classification (of this page) Unclassified |
21. No. of Pages
46 |
22. Price
N/A |
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| Form DOT F 1700.7 (8-72) | Reproduction of completed page authorized |
