The frustration of getting stuck behind a slow vehicle on a remote road is all too familiar to drivers in Pennsylvania, where rural roads make up about 60% of highways. One of the roadway features that addresses this issue are passing zones - dotted sections of two-lane roadways that allow for vehicles to cross into the opposing lane of traffic to pass other vehicles - but are they safe?
"There's been some studies completed on the safety impact of dedicated passing lanes, but none for passing zones," said Eric Donnell, senior associate dean of the Penn State College of Engineering and professor of civil and environmental engineering, who recently co-authored a paper on the topic. "The more that we looked through state and federal traffic safety resources like Highway Safety Manual, the more we noticed there was a lack of data, which really drove us to pursue this research."
Donnell and his collaborators at Penn State used a large data set of Pennsylvania Department of Transportation (PennDOT)-provided crash statistics and roadway features taken from all state-owned, rural roads to compare the safety performance of roadway segments with passing zones to stretches without marked passing zones. Their computational analysis revealed 11% fewer total crashes, and 12% fewer crashes leading to significant injury or fatalities on sections of rural highway marked as passing zones compared to sections of road marked as no passing. The study, available online now, is set to publish in the September issue of Accident Analysis and Prevention.
According to Vikash Gayah, director of the Larson Transportation Institute, professor of civil and environmental engineering and co-author on the paper, roadway experts already suspected that passing zones had a significant impact on road safety, but did not have a system to accurately quantify their impact.
"In previous work, these passing zones continually came up as areas that experienced fewer reported crashes than other sections of road," Gayah said. "We knew where all the passing zones were and knew that they were associated with fewer crashes, but this was an opportunity to really dig into the data."
