Study Details

Study Title: In-Service Performance Evaluation (ISPE) for G4 (1S) Type of Strong-Post W-Beam Guardrail System and Cable Median Barrier: Volume II

Authors: Alluri, P., K. Hallem, and A. Gan.

Publication Date:DEC, 2012

Abstract: This report presents a study to evaluate the safety performance of cable median barriers on limited access facilities in Florida. A companion report (Volume I) focuses on the performance of the G4 (1S) type of strong-post W-beam guardrails in Florida. In this study, the performance of cable median barriers was evaluated based mainly on two types of analysis: (1) the percentages of barrier and median crossovers by site location, vehicle type, crash severity, and cable median barrier type; and (2) comparisons of median-related crash statistics before and after cable median barrier installations by crash severity and vehicle type. Twenty-three locations with cable median barriers totaling about 101 miles were identified. Police reports of 8,818 crashes from years 2003 - 2010 at these locations were reviewed to verify and obtain detailed crash information. A total of 549 crashes were determined to be barrier crashes (i.e., involving vehicles hitting a barrier) and were reviewed in further detail to identify crossover crashes and the manner in which the vehicles crossed the barriers, i.e., either by over-riding, under-riding, or penetrating the barriers. Of the 549 barrier crashes, 16.4% (90) were found to have crossed over the barriers, and 83.6% were either contained or redirected by the barriers. Of the 90 crashes that involved vehicles crossing the barrier, 14 crashes resulted in vehicles crossing the median into the opposite travel lane. Overall, 98.1% of cars and 95.5% of light trucks that hit the barrier were prevented from crossing the median. The before-and-after analysis was based on only median-related crashes (i.e., involving vehicles leaving the travel lane toward the median) to more precisely evaluate the impacts of cable median barrier installation and ensure that the results are not affected by unrelated crashes. The analysis included 744 median-related crashes at three locations totaling 36 miles. The results show that cable median barrier installation reduced fatal crash rate by 42.2%, severe injury crash rate by 20.1%, and minor injury crash rate by 11.6%, but increased the crash rates involving possible injury and property damage by 53.1% and 88.1%, respectively, for an overall crash increase of 37.8%.

Study Citation: Alluri, P., K. Hallem, and A. Gan. In-Service Performance Evaluation (ISPE)for G4 (1S) Type of Strong-Post W-Beam Guardrail System and Cable Median Barrier: Volume II. Florida DOT. December 2012.

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Roadside

Countermeasure: Install cable median barrier (high tension)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.57842.22 StarsOtherKPrincipal Arterial Other Freeways and Expressways
0.79920.11 StarOtherAPrincipal Arterial Other Freeways and Expressways
0.88411.62 StarsOtherBPrincipal Arterial Other Freeways and Expressways
1.881-88.12 StarsOtherOPrincipal Arterial Other Freeways and Expressways
1.378-37.82 StarsOtherAllPrincipal Arterial Other Freeways and Expressways