Study Details

Study Title: Development of Crash Modification Factors of Alignment Elements and Safety Countermeasures for Korean Freeways

Authors: Choi et al.

Publication Date: JAN, 2015

Abstract: Recently, many efforts have been devoted to improving the safety of freeways in Korea, as freeways are the most important roadways in the transportation network. As a part of these efforts, this research aims to develop crash modification factors (CMFs) of two alignment elements, as well as eight safety countermeasures for Korean freeways. To do this, classical safety performance functions (SPFs) for each freeway were developed. To develop the CMFs of two alignment elements, horizontal curve and vertical grade, we also estimated inclusive SPFs that include the alignment elements together with traffic volume and segment length as independent variables. The CMFs of horizontal curve and vertical grade were calculated as the marginal effect of their coefficients on the inclusive SPFs. Then, eight CMFs for safety countermeasures including delineator posts, automated speed enforcement cameras, rumble strips, chevron signs, roadside barriers, grooving, illumination and median barriers were developed. The regression-to-the-mean (RTM) bias, time trend of crash count, and effect of traffic volume change were corrected by using the empirical Bayes (EB) method. The developed CMFs in this study were compared with those from previous literature and discussed the findings from the comparison. The results from this study contribute to enhancing the safety of Korean freeways and act as a reference guide for other Korean roadways, as well as roadways in other countries.

Study Citation: Choi, Y-Y., S-Y. Kho, C. Lee, and D-K, Kim. "Development of Crash Modification Factors of Alignment Elements and Safety Countermeasures for Korean Freeways". Presented at the 94th Annual Meeting of the Transportation Research Board, Paper No. 05-0503, Washington, D.C., (2015).


CMFs Associated With This Study

Category: Advanced technology and ITS

Countermeasure: Implement automated speed enforcement cameras

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.942 5.8 4 Stars All All Principal Arterial Other Freeways and Expressways

Category:Alignment

Countermeasure: Change horizontal alignment from R1 to R2

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
CMF Equation CRF Equation 3 Stars All All Principal Arterial Other Freeways and Expressways

Countermeasure: Change negative vertical grade from G1 to G2

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
CMF Equation CRF Equation 3 Stars All All Principal Arterial Other Freeways and Expressways

Countermeasure: Change positive vertical grade from G1 to G2

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
CMF Equation CRF Equation 3 Stars All All Principal Arterial Other Freeways and Expressways

Category:Delineation

Countermeasure: Install post-mounted delineators

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.19 -19 4 Stars All All Principal Arterial Other Freeways and Expressways

Category:Highway lighting

Countermeasure: Install lighting

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.922 7.8 3 Stars All All Principal Arterial Other Freeways and Expressways

Category:Roadside

Countermeasure: Install median barrier

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.226 -22.6 3 Stars All All Principal Arterial Other Freeways and Expressways

Countermeasure: Install roadside barrier

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.908 9.2 3 Stars All All Principal Arterial Other Freeways and Expressways

Category:Roadway

Countermeasure: Resurface pavement with groove pavement (GP)

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.891 10.9 3 Stars All All Principal Arterial Other Freeways and Expressways

Category:Shoulder treatments

Countermeasure: Install shoulder rumble strips

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.752 24.8 4 Stars All All Principal Arterial Other Freeways and Expressways

Category:Signs

Countermeasure: Install chevron signs on horizontal curves

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.721 27.9 3 Stars All All Principal Arterial Other Freeways and Expressways