Over half of motor vehicle fatalities are roadway departures, with rural horizontal curves being of particular interest because they make up only a small share of the system mileage but have a crash rate that is three times higher than tangent sections. Although transportation agencies expend significant resources to address the problem, the interaction between the driver and roadway environment is not well understood, and, as a result, it is difficult to select appropriate countermeasures. In order to address this knowledge gap, data from the SHRP 2 NDS and RID were used to develop relationships between driver, roadway, and environmental characteristics and risk of a road departure on rural curves. Only curves on rural two-lane paved roadways with posted speed limits of 72.4 to 88.5 kph (45 to 55 mph) were included. The research was tailored to address four fundamental research questions: 1. What defines the curve area of influence? 2. What defines normal behaviour on curves? 3. What is the relationship between driver-distractions; other driver, roadway, and environmental characteristics; and risk of roadway departure? 4. Can lane position at a particular state be predicted as a function of position in a prior state? Each question addresses the problem from a different perspective, and, as a result, a different methodology was proposed for each. (Author/publisher)
Abstract