Creating rural road safety strategies that go beyond crash history
The transportation safety community has largely embraced a data-driven approach to highway safety, but this approach traditionally relies on “worst first” analysis based on crash history data. Unfortunately, the traditional approach of using crash history alone does not always provide results, because serious crashes on the rural system are infrequent and appear to occur at random locations as a result of their low density. Now, however, transportation engineers are beginning to turn to a new “systemic” safety approach to reduce serious injury and fatal crashes on rural highway systems.
In a September 8 Roadway Safety Institute seminar, St. Louis County (Minnesota) traffic engineer Vic Lund described how Minnesota transportation engineers have recently begun applying this new systemic safety approach to rural highway safety on county and state highways.
“What we are doing with a systemic safety approach is similar to what doctors have been doing for a long time,” Lund said. “They ask about your health history, diet, and behaviors to assess your risk for developing certain diseases, then help you find a way to proactively address those risks so you don’t have to deal with more serious issues later in life.”
The systemic safety approach considers the metric of risk versus the traditional metric of crash history. Determining the risk of a highway facility requires considering characteristics such as geometry, traffic volume, and presence of key features such as railroad crossings. Then, network screening allows for the identification of high-risk locations.
“For example, we know that one of the most likely places for a serious injury or fatal crash to occur on a rural road is a four-legged, two-way-stop intersection, and that some additional risk factors for these intersections include skew, curve, distance to previous stop signs, and nearby railroad crossings,” Lund noted. “We can then rank all of our two-way-stop intersections based on risk and deploy proven, low-cost safety measures for every at-risk location within our system.”
According to Lund, a systemic approach offers a number of important advantages. First, it identifies a “problem” based on a system-wide analysis of data and then looks for the roadway characteristics that are frequently present in serious crashes, which become the risk factors. Next, it focuses on one or more proven, low-cost countermeasures that can be deployed across the entire system. Finally, it identifies and prioritizes locations across the network for implementation.
“The traditional approach says that ‘crashes equal risk’ and ‘no crashes equal no risk,’ while the systemic approach recognizes this is not the case,” Lund said. “When we use a systemic approach to focus safety strategies at high-risk locations—which are the minority of the system—we can start having an impact on the majority of crashes and make real progress towards our goal of toward zero deaths on Minnesota roadways.”