Examination of Features Correlated With Roadway Departure Crashes on Rural Roads

Report No: 21-R2

Published in 2020

About the report:

Roadway departure (RD) crashes are one of the major causes of fatalities on highways.  Reducing the number and severity of RD crashes is one of the emphasis areas of the strategic highway safety plan for many state departments of transportation in the United States.  Many significant efforts have been aimed at reducing RD crashes, and a continued focus on preventing these crashes is needed.  The purpose of this study was to identify roadway geometric design, roadside, and traffic characteristics that are correlated with RD crashes on rural roads.  Using data collected in Virginia from 2014-2018, this study analyzed the characteristics of RD crashes on rural roadways and identified how the variation in RD crash frequency and severity is related to roadway, roadside, and traffic features.

The study found a significant correlation between the frequency of RD crashes and annual average daily traffic, shoulder width, and speed limit. The number of RD crashes increased as the annual average daily traffic and speed limit increased and decreased as the shoulder width was increased.  Further analysis using more granular data from two fairly recent data sources, SCRIM and iVision, showed promise for further insights into factors influencing RD crashes.  In particular, the results showed that these crashes are significantly influenced by roadway geometry (curvature and cross slope) and pavement condition (skid resistance and roughness).

Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.

Last updated: November 9, 2023

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