Study Details
Study Title: Reducing Roadway Departure Crashes at Horizontal Curve Sections on Two-lane Rural Highways
Authors: Donnell et al.
Publication Date:JAN, 2019
Abstract: While several proven safety countermeasures and strategies exist to mitigate roadway departure crashes on horizontal curve sections of two-lane rural highways, there are several countermeasures or strategies that have yet to be proven via a rigorous safety evaluation. The purpose of this research was to identify several of these strategies or countermeasures, and to perform a statistical assessment of their safety effectiveness. This report details the following three evaluations: (1) observational before-after study of curve ahead warning pavement markings, (2) cross-sectional study of delineators on guiderail along horizontal curves, and (3) cross-sectional study of the safety effects of geometric design consistency. The findings from these evaluations indicate that the expected number of roadway departure crashes are associated with the horizontal curve radius, radii of adjacent horizontal curves, and the tangent lengths between curves. Further, the expected number of roadway departure crashes is associated with side friction demand on horizontal curves. Guiderail with delineators are expected to reduce total, fatal plus injury, run-off-road (ROR), and nighttime crashes along horizontal curves that are four degrees or sharper. Horizontal curve warning pavement markings are associated with fewer expected total, fatal plus injury, ROR, nighttime, nighttime ROR, and nighttime fatal plus injury crashes on two-lane rural highways.
Study Citation: Donnell, E., R.J. Porter, L. Li, I. Hamilton, S.C. Himes, and J. Wood. "Reducing Roadway Departure Crashes at Horizontal Curve Sections on Two-lane Rural Highways". Report No. FHWA-SA-19-005. Federal Highway Administration, U.S. Department of Transportation. Washington, D.C. (January 2019).
Related Citations: Himes, S., R.J. Porter, I. Hamilton, and E. Donnell. "Safety Evaluation of Geometric Design Criteria: Horizontal Curve Radius and Side Friction Demand on Rural, Two-Lane Highways". Presented at the 98th Annual Meeting of the Transportation Research Board, Paper No. 19-05022, Washington, D.C., (2019).
CMFs Associated With This Study
Category: Alignment
Countermeasure: Change horizontal alignment
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
 | |  | Fixed object,Head on,Run off road,Sideswipe | All | Not specified | Rural |
| | | Fixed object,Head on,Run off road,Sideswipe | K,A,B,C | Not specified | Rural |
Countermeasure: Change horizontal curve radius, posted speed and superelevation
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
| | | Fixed object,Head on,Run off road,Sideswipe | All | Not specified | Rural |
Category:Delineation
Countermeasure: Install in-lane curve warning pavement markings
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
| 0.652 | 34.8 |  | All | All | Not specified | Rural |
Category:Roadside
Countermeasure: Install guiderail
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
| 0.845 | 15.5 |  | All | All | Not specified | Rural |
Countermeasure: Install guiderail with delineators
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
| 0.971 | 2.9 | | All | All | Not specified | Rural |
