Study Details

Study Title: Estimating Crash Modification Factors Using Cross-Sectional and Case-Control Methods for Rumble Strips and Paved Shoulders

Authors: Galgamuwa and Dissanayake

Publication Date: JAN, 2017

Abstract: This paper describes the application of case-control and cross-sectional methods to develop crash modification factors (CMFs) for lane departure countermeasures in two-lane rural undivided road segments in Kansas. Four commonly used countermeasures, namely 2-ft paved shoulders, centerline rumble strips, shoulder rumble strips, and shoulder & centerline rumble strips have been considered. CMFs were calculated for all severity and fatal & injury lane departure crashes. Generalized linear regression assuming a negative binomial error structure and logistic regression were used in developing models for cross-sectional and case-control methods respectively. Mean residuals and mean squared error (MSE) were used to validate the models developed for cross-sectional method. Classification tables were used to validate the models developed for case-control method. Cross-sectional method shows that all the countermeasures considered in this study were effective in reducing all severity and fatal & injury lane departure crashes. However, the range of CMF includes 1, for the shoulder rumble strips on curved road segments for all crash severities, which indicates that it has some crash increasing effect. The case-control study also shows that all the countermeasures have a crash reduction effect except shoulder rumble strips on curved road segments for all crash severities. Even though similar results were obtained from both methods, CMFs developed using the cross-sectional method demonstrated a narrower range than the case-control method indicating that the results from the cross-sectional method can be considered as more accurate and reliable than those from case control method.

Study Citation: 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).


CMFs Associated With This Study

Category: Roadway

Countermeasure: Install centerline and shoulder rumble strips

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.86 14 3 Stars Head on,Run off road,Sideswipe All Not specified Rural
0.94 6 3 Stars Head on,Run off road,Sideswipe K,A,B,C Not specified Rural
0.89 11 3 Stars Head on,Run off road,Sideswipe All Not specified Rural
0.87 13 3 Stars Head on,Run off road,Sideswipe K,A,B,C Not specified Rural

Countermeasure: Install centerline rumble strips on horizontal curves

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.94 6 3 Stars Head on,Run off road,Sideswipe All Not specified Rural
0.95 5 3 Stars Head on,Run off road,Sideswipe K,A,B,C Not specified Rural

Countermeasure: Install centerline rumble strips on tangent sections

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.96 4 3 Stars Head on,Run off road,Sideswipe All Not specified Rural
0.96 4 3 Stars Head on,Run off road,Sideswipe K,A,B,C Not specified Rural

Category:Shoulder treatments

Countermeasure: Install shoulder rumble strips (horizontal curves)

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.95 5 3 Stars Head on,Run off road,Sideswipe All Not specified Rural
0.94 6 3 Stars Head on,Run off road,Sideswipe K,A,B,C Not specified Rural

Countermeasure: Install shoulder rumble strips (tangents)

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.94 6 3 Stars Head on,Run off road,Sideswipe All Not specified Rural
0.95 5 3 Stars Head on,Run off road,Sideswipe K,A,B,C Not specified Rural

Countermeasure: Provide 2-ft paved shoulders (both sides)

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.88 12 3 Stars Head on,Run off road,Sideswipe All Not specified Rural
0.94 6 3 Stars Head on,Run off road,Sideswipe K,A,B,C Not specified Rural
0.89 11 3 Stars Head on,Run off road,Sideswipe All Not specified Rural
0.93 7 3 Stars Head on,Run off road,Sideswipe K,A,B,C Not specified Rural