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Coordinating, Developing, and Delivering Highway Transportation Innovations

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Publication Number:  FHWA-HRT-20-035    Date:  April 2020
Publication Number: FHWA-HRT-20-035
Date: April 2020


Research Utilizing SHRP2 Data to Improve Highway Safety: Development of Speed - Safety Relationships

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In 2016, the Federal Highway Administration posted a broad agency announcement (BAA) to conduct research on potential safety improvements using the Naturalistic Driving Study (NDS) and the Roadway Information Database (RID), resources developed from data collected during the research phase of the second Strategic Highway Research Program. Phase 1 served as a proof of concept to determine if meaningful conclusions or countermeasures could be developed using the NDS and the RID. Phase 2 enabled researchers to conduct more indepth analyses, leading to specific highway safety improvements.

The following final report describes the methodology and results of one of six BAA projects to evaluate the relationship between speed and safety of urban and suburban arterials affected by roadway and roadside characteristics. In this study, researchers used the NDS and the RID to correlate speed with several roadway and roadside variables and found that the crash likelihood increases as the variance of mean speed increases for a given roadway segment. Furthermore, the inclusion of the speed term in the existing Highway Safety Manual safety-prediction models for urban and suburban arterials does not improve the predictions.

This report will be of interest to State and local department of transportation safety professionals interested in relationships between roadway design, speed, and safety.

Brian P. Cronin, P.E.
Director, Office of Safety and Operations
Research and Development


This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.

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Technical Report Documentation Page
1. Report No.
2. Government Accession No. 3. Recipient’s Catalog No.
4. Title and Subtitle
Research Utilizing SHRP2 Data to Improve Highway Safety: Development of Speed—Safety Relationships
5. Report Date
April 2020
6. Performing Organization Code
7. Author(s)
J.M. Hutton, D. Cook, J. Grotheer, and M. Conn
8. Performing Organization Report No.
9. Performing Organization Name and Address
425 Volker Boulevard
Kansas City, MO 64110–2241
10. Work Unit No. (TRAIS)
11. Contract or Grant No.
12. Sponsoring Agency Name and Address
Office of Safety Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101–2296
13. Type of Report and Period Covered
Final Report; November 2015–July 2019
14. Sponsoring Agency Code
15. Supplementary Notes
The Task Order Contracting Officer's Representative is Yusuf Mohamedshah (HRDS-20, ORCID: 0000-0003-0105-5559).
16. Abstract

The objective of this research was to examine the link between driving speed and crash experience on roadway segments, taking into account roadway characteristics that influence speed and crash frequency and severity. A potential outcome of the research was improved safety performance functions that included a speed term or crash modification factors (CMFs) based on speed for use in a safety-prediction methodology for urban/suburban arterials. Using the second Strategic Highway Research Program Naturalistic Driving Study data and the Roadway Inventory Database (RID), the research examined individual drivers' speeds along 100 study segments. Variations within individual trips as well as among drivers on the same roadway segment over a few years were evaluated. Also, using the RID and roadway and roadside characteristics obtained from aerial and street-view imagery, relationships between speed choice and roadway characteristics were explored. The research found that a number of roadway characteristics are related to speed and crash experience for a roadway segment and that a higher measure of speed variance between trips was frequently correlated with higher crash frequency (especially for multivehicle crashes). Most other speed measures evaluated had no correlation with crash frequency or had a negative correlation. The research did not find that including a speed term into existing safety performance functions or developing a speed CMF would substantially improve the existing crash-prediction methodology for urban and suburban arterials presented in the Highway Safety Manual.

17. Key Words
Highway safety, suburban arterial, speed, crash modification factor, urban arterial, crash data, naturalistic driving, roadway inventory data
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
19. Security Classif. (of this report)
20. Security Classif. (of this page)
21. No. of Pages
22. Price
Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized.
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