Research Report
Karin M. Bauer, Douglas W. Harwood
Jan-14
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.
Safety Effects of Horizontal Curve and Grade Combinations on Rural Two-Lane Highways
Safety
Horizontal curves
Vertical curves
Grade
interaction
Crests
Sags
Rural two-lane highways
Crash modeling
Safety performance function
Crash
modification factor
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.
A variety of research studies have been performed using data from HSIS. Many of the final reports prepared are now available electronically.
Research reports are often summarized in executive summaries, technical briefs, or other abbreviated formats. Included here are those road safety summaries that involved research using HSIS data.
In addition to conducting research, HSIS resources are also used to develop products that can be used by practitioners in the analysis of safety problems.
HSIS data are sometimes used in research studies that result in other types of finished products, such as dissertations, theses, and conference proceedings.
