U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000


Skip to content
Facebook iconYouTube iconTwitter iconFlickr iconLinkedInInstagram

Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations

 
REPORT
This report is an archived publication and may contain dated technical, contact, and link information
Back to Publication List        
Publication Number:  FHWA-HRT-17-070    Date:  August 2017
Publication Number: FHWA-HRT-17-070
Date: August 2017

 

Safety Evaluation of Cable Median Barriers in Combination With Rumble Strips on Divided Roads

CHAPTER 2. OBJECTIVE

The research for this study examined the safety impacts of cable median barriers with inside shoulder rumble strips in Illinois, Kentucky, and Missouri. The objective of the study was to estimate the safety effectiveness of this strategy as measured by crash frequency. The primary target crash type was cross-median crashes, and the analysis excluded intersection-related and animal crashes.

In addition to cross-median crashes, the research team considered total injury and fatal, median-related, ROR left side, and winter-related crashes. Median-related crashes are those in which the vehicle does not cross the median but ends up in the median after a rollover and/or a collision with an object. Based on the available variables in the crash databases from the States, the research team was not able to determine whether a crash was median-related. Similarly, the research team could not determine run-off-left-side crashes from the crash reports. Consequently, the evaluation did not specifically examine these crash types. The evaluation examined winter-related crashes, but because the sample of crashes was very small, the research team did not report the results here.

It is important to note that the treatment itself was not exactly the same in the three evaluated States. In Illinois and Kentucky, the introduction of cable median barriers came many years after the introduction of rumble strips on inside shoulders. Conversely, Missouri installed cable median barriers and inside shoulder rumble strips about the same time. The before–after conditions in the three States can be summarized as follows:

In addition to determining the overall safety effect of the treatment(s), a further objective was to address the following questions:

The evaluation of overall effectiveness included consideration of the installation costs and crash savings in terms of the B/C ratio.

Meeting these objectives placed some special requirements on the data collection and analysis tasks, including the need to do the following:

 

 

Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000
Turner-Fairbank Highway Research Center | 6300 Georgetown Pike | McLean, VA | 22101