High-tensioned cable barriers have only recently been introduced in the United States as a median barrier option, primarily as a result of state agencies looking for a cost-effective means with which to mitigate or eliminate cross-median crashes. Few studies, however, provide a means with which to estimate the frequency and severity of a roadway segment with cable barriers. A combination of a before-and-after analysis with negative binomial and logistic regression was applied to data obtained from eight states to investigate the impact of cable barriers on the frequency and severity of crashes on a roadway segment. Three types of crashes were investigatedfor both the frequency and severity of crashes: single vehicle, multiple-vehicle same-direction, and multiple-vehicle opposite-direction, also called cross-median or cross-over crashes. These three crash categories were considered separately with the assumption (confirmed with the results) thatthey are affected by the presence of the median barrier differently. The results indicate that an installation of cable barriers, both low and high-tensioned, eliminates more than 90% of multiple vehicle – opposite direction crashes. The before-and-after analysis showed that this median treatment results in an increase in single vehicle crashes by about 80% and a weak if any effect on the frequency of multiple vehicle – same direction crashes. Considering severity, the proportion of severe crashes, in general, decreases by 8% with the installation of a low tensioned cable barrier. The effect of high-tensioned cables on severity measured with the proportionof injury and fatal crashes seems to be negligible.
Samenvatting