Turner-Fairbank Highway Research Center

 
 
 
 
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Safety Effects of Horizontal Curve and Grade Combinations on Rural Two-Lane Highways

Product Type

Research Report

Author

Karin M. Bauer, Douglas W. Harwood

Date

Jan-14

Abstract

This report summarizes the results of research undertaken to quantify the safety effects of five types of horizontal and vertical alignment combinations for rural two-lane highways. The research is based on Federal Highway Administration Highway Safety Information System data for Washington State, including crash records from 2003 to 2008. The outcome is a set of safety prediction models for fatal and injury and property damage only crashes. To present the results in a form suitable for incorporation in the American Association of State Highway and Transportation Officials Highway Safety Manual, crash modification factors representing safety performance relative to level tangents were developed from these models for each of the five combinations of horizontal and vertical alignment—horizontal curves and tangents on straight grades, horizontal curves and tangents at type 1 crest vertical curves, horizontal curves and tangents at type 1 sag vertical curves, horizontal curves and tangents at type 2 crest vertical curves, and horizontal curves and tangents at type 2 sag vertical curves.

Link To Research Report

Safety Effects of Horizontal Curve and Grade Combinations on Rural Two-Lane Highways

Keywords

Safety
Horizontal curves
Vertical curves
Grade interaction
Crests
Sags
Rural two-lane highways
Crash modeling
Safety performance function
Crash modification factor


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HSIS Summaries

HSIS Summary Reports are two to eight pages in length and include a brief description of the issue addressed, data used, methodology applied, significant results, and practical implications.

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