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(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
---|
0.85 | 15 | | Run off road | All | Not specified | Rural |
0.9 | 10 | | Run off road | K,A,B,C | Not specified | Rural |
Category:Roadside
Countermeasure: Install cable median barrier
CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
---|
0.5 | 50 | | All | All | Not specified | Not specified |
0.82 | 18 | | Run off road | K,A,B,C | Not specified | Not specified |
Category:Shoulder treatments
Countermeasure: Install safety edge treatment
CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
---|
0.892 | 10.8 | | Run off road | All | Not specified | Rural |
0.648 | 35.2 | | Run off road | K,A,B,C | Not specified | Rural |
Countermeasure: Install shoulder rumble strips
CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
---|
0.91 | 9 | | Run off road | All | Not specified | All |
0.96 | 4 | | Run off road | All | Not specified | All |
0.5 | 50 | | Run off road | K,A,B,C | Not specified | All |
0.3 | 70 | | Run off road | K,A,B,C | Not specified | All |
Countermeasure: Pave shoulder
CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
---|
1.07 | -7 | | Run off road | All | Not specified | All |
0.84 | 16 | | Run off road | All | Not specified | All |
0.7 | 30 | | Run off road | K,A,B,C | Not specified | All |
0.35 | 65 | | Run off road | K,A,B,C | Not specified | All |
Category:Signs
Countermeasure: Install chevron signs on horizontal curves
CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
---|
0.89 | 11 | | Run off road | All | Not specified | Rural |
0.88 | 12 | | Run off road | K,A,B,C | Not specified | Rural |