Study Details
Study Title: Is Horizontal Curvature a Significant Factor of Safety in Rural Multilane Highways?
Authors: Banihashemi
Publication Date:JAN, 2015
Abstract: The Highway Safety Manual (HSM) crash prediction models estimate the expected number of crashes for different facility types. Models in Part C of the first edition of the HSM include crash prediction models for divided and undivided rural multilane highway segments. Each of the HSM crash prediction models for highway segments is comprised of a "Safety Performance Function" (SPF) that is a function of AADT and segment length plus, a series of "Crash Modification Factors" (CMFs). The SPF estimates the number of crashes for the site if the site features are of base condition. The effects of the other features of the site, if their values are different from base condition, are carried out through use of CMFs. The existing models for rural multilane segments do not have any CMF for horizontal curvature. The goal of this research is to investigate if the horizontal alignment has any significant effect on crashes on these types of facilities and if so, to develop a CMF for this feature. Washington State cross sectional data from the Highway Safety Information System (HSIS) lab is used in this research. Data from 2007 to 2009 is used to do the investigation. The 2010 and 2011 data is used to validate the results. As the results show the horizontal curvature has significant safety effect on rural multilane highways and using a CMF for horizontal curvature improves the prediction of crashes significantly, for both tangent and curve segments.
Study Citation: Banihashemi,M. "Is Horizontal Curvature a Significant Factor of Safety in Rural Multilane Highways?" Presented at the 94th Annual Meeting of the Transportation Research Board, Paper No. 15-1783, Washington, D.C., (2015).
CMFs Associated With This Study
Category: Alignment
Countermeasure: Change horizontal alignment
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
 |  | All | All | All | Rural |
