Study Details
Study Title: Safety Evaluation of Truck-Related Crashes at Freeway Diverge Areas
Authors: Zhenyu Wang, Bin Cao, Weiping Deng, Jian John Lu, and Zhao Zhang
Publication Date:JAN, 2011
Abstract: The study evaluated the impacts of geometric design factors and traffic factors on the truck-related crashes at freeway diverge areas. For this purpose, 391 freeway segments with different geometric designs were selected in various locations throughout the State of Florida. Crash data and inventory data were collected from the selected freeway segments and organized into two sets: site-based and crash-based for developing two prediction models (truck-related crash frequency model and truck-related injury severity model) respectively. The truck-related crash frequency model, fitted by the Negative Binominal regression, is used to identify the significant factors contributing to truck-related crash frequency at freeway diverge areas, and quantify the impacts of the factors. And the injury severity model, developed by the Ordered Probit regression, is utilized to address the factors that contribute to the injury severity of truck-related crashes at freeway diverge areas and the factor impacts. The analysis of the two models show that exit configurations (Type I, II, III and IV) have no significant influence on the injury severity of truck-related crashes at diverge areas. Type III exit configuration has the best safety performance in terms of the lowest truck-related crash frequency at freeway diverge areas. For one-lane freeway exit ramp, replacing a Type I exit configuration with a Type II exit configuration will increase truck-related crash counts at freeway diverge area by 21%. For two-lane exit ramps, replacing a Type III configuration with a Type IV configuration will increase crash counts at freeway diverge area by 26%. Other significant factors on truck-related crashes at freeway diverge areas include deceleration lane length, number of through lanes/surface width, median/shoulder width, curvature and grade design, speed limit, AADT on mainline/ramp, and truck percentage.
Study Citation: Wang, Z., B. Cao, W. Deng, J.J. Lu, and Z. Zhang. "Safety Evaluation of Truck-Related Crashes at Freeway Diverge Areas." TRB 90th Annual Meeting Compendium of Papers. Washington, D.C. 2011.
CMFs Associated With This Study
Category: Interchange design
Countermeasure: Convert a Type I exit ramp to a Type II exit ramp
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 1.21 | -21 |  | Truck related | All | Principal Arterial Other Freeways and Expressways | Not specified |
Countermeasure: Convert a Type I exit ramp to a Type III exit ramp
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.79 | 21 | | Truck related | All | Principal Arterial Other Freeways and Expressways | Not specified |
Countermeasure: Convert a Type I exit ramp to a Type IV exit ramp
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 1 | 0 |  | Truck related | All | Principal Arterial Other Freeways and Expressways | Not specified |
Countermeasure: Convert a Type III exit ramp to a Type IV exit ramp
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 1.26 | -26 | | Truck related | All | Principal Arterial Other Freeways and Expressways | Not specified |
Category:Roadway
Countermeasure: Increase surface width from X to Y feet
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
 | | | Truck related | All | Principal Arterial Other Freeways and Expressways | Not specified |
Category:Shoulder treatments
Countermeasure: Widen paved shoulder from X to Y ft
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| | | Truck related | All | Principal Arterial Other Freeways and Expressways | Not specified |
Category:Speed management
Countermeasure: Increase speed limit from X to Y mph
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| | | Truck related | All | Principal Arterial Other Freeways and Expressways | Not specified |
