Improving Safety at High-Speed Rural Intersections

The Indiana Department of Transportation (INDOT) prepares annual reports that identify intersections and segments on state roads that require attention due to the excessive number and severity of crashes. Many of these identified intersections are two-way stop-controlled (TWSC) intersections on rural multi-lane roads with 55 or 60 mi/h speed limits. Various road design and human factors may contribute to the troublesome level of safety at Indiana high-speed rural intersections. Some of these safety factors have already been identified while other factors still await identification. This paper looks first at past research on safety at high-speed intersections to learn about known safety factors and to identify proven and proposed countermeasures. Next, extensive data, representing 557 Indiana TWSC intersections, are analyzed with statistical modeling to reevaluate some of the safety countermeasures found in the literature and to identify new ones. The developed trivariate ordered probit model estimates the effects of design, traffic, and land-use variables on crash severity and frequency at the studied intersections. The results are then used to estimate the possible reduction of fatal, injury, and property damage crashes associated with certain modifications of intersection geometry. Our findings show that adding acceleration lanes, increasing the intersection angle, widening medians more than 80 feet, and improving the recognizability of intersections considerably contribute to improving intersection safety.