Study Details

Study Title: Estimating Crash Modification Factors for Lane Departure Countermeasures in Kansas

Authors: Dissanayake and Galgamuwa

Publication Date:DEC, 2017

Abstract: This project was conducted to estimate crash modification factors (CMFs) for lane departure countermeasures in Kansas. Cross- sectional, case-control, and before-and-after empirical Bayes (EB) methods were employed. Results showed that centerline rumble strips on rural two-lane road segments have crash-reduction effects on all lane departure and fatal and injury lane departure crashes on both tangent and curved road segments. Shoulder rumble strips were effective in reducing all lane departure and fatal and injury lane departure crashes on tangent road segments but showed less effectiveness on curved road segments. The combination of centerline and shoulder rumble strips showed significant safety effectiveness on both tangent and curved road segments. Shoulder rumble strips on four-lane road segments also showed crash-reduction effects on all lane departure and fatal and injury lane departure crashes on both tangent and curved road segments. Cable median barriers showed a crash-reduction effect on all lane departure crashes, and fatal and injury lane departure crashes on four-lane divided road segments. Chevrons and post- mounted delineators also showed effectiveness on both all lane departure crashes and fatal and injury lane departure crashes. The safety edge treatment also showed a crash-reduction effect on all lane departure crashes and fatal and injury lane departure crashes. Finally, all models were validated to check for accuracy. Models developed for the cross-sectional method were validated using mean square error and mean of the residuals. Case-control models werevalidated using the specificity, accuracy, and sensitivity ignificance of the CMFs developed using the before-and-after EB method was realized using the method given in the Highway Safety Manual.

Study Citation: Dissanayake, S. and U. Galgamuwa. "Estimating Crash Modification Factors for Lane Departure Countermeasures in Kansas." Center for Transportation Research and Education, Iowa State University, Ames, IA. (December 2017).

Related Citations: Galgamuwa, U., and S. Dissanayake. "Estimating Crash Modification Factors Using Cross-Sectional and Case-Control Methods for Rumble Strips and Paved Shoulders". Presented at the 96th Annual Meeting of the Transportation Research Board, Paper No. 17-01474, Washington, D.C., (2017).

Study Report: Download the Study Report Document

Comments: The authors provided CMFs for both cross-sectional and case-control models. The Clearinghouse team decided to include only the cross-sectional model results as the team felt they were the more reliable models. The authors do not recommend one over the other, but they do note that the case-control model assumes crash cases versus no crash case and does not properly address crash counts, indicating the methodology is best for low crash counts (i.e., 1s and 0s).


CMFs Associated With This Study

Category: Delineation

Countermeasure: Install post-mounted delineators

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.85152 StarsRun off roadAllNot specifiedRural
0.9102 StarsRun off roadK,A,B,CNot specifiedRural

Category:Roadside

Countermeasure: Install cable median barrier

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.5502 StarsAllAllNot specifiedNot specified
0.82182 StarsRun off roadK,A,B,CNot specifiedNot specified

Category:Shoulder treatments

Countermeasure: Install safety edge treatment

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.89210.83 StarsRun off roadAllNot specifiedRural
0.64835.23 StarsRun off roadK,A,B,CNot specifiedRural

Countermeasure: Install shoulder rumble strips

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.9192 StarsRun off roadAllNot specifiedAll
0.9642 StarsRun off roadAllNot specifiedAll
0.5502 StarsRun off roadK,A,B,CNot specifiedAll
0.3702 StarsRun off roadK,A,B,CNot specifiedAll

Countermeasure: Pave shoulder

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.07-72 StarsRun off roadAllNot specifiedAll
0.84162 StarsRun off roadAllNot specifiedAll
0.7302 StarsRun off roadK,A,B,CNot specifiedAll
0.35652 StarsRun off roadK,A,B,CNot specifiedAll

Category:Signs

Countermeasure: Install chevron signs on horizontal curves

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.89112 StarsRun off roadAllNot specifiedRural
0.88122 StarsRun off roadK,A,B,CNot specifiedRural