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 |  | 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 |
|---|---|---|---|---|---|---|
 | | | 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 |
|---|---|---|---|---|---|---|
| | | 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 |
|---|---|---|---|---|---|---|
| | | 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 | | 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 |  | 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 | | 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 | | 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 | | 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 |  | 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 | | All | All | Principal Arterial Other Freeways and Expressways |
