This research project examines the safety performance of unsignalized intersections on rural divided highways in Alabama. A summary of the safety problem at these intersections is provided; the concern is the relatively high frequency and severity of crashes at these locations, typically associated with vehicles entering from the minor road and failing to successfully cross or turn left onto the second directional roadway. The project objectives included review of the literature, examination of a small set of such intersections in Alabama with innovative treatments, factors that influence safety performance and approaches to estimating performance, and developing design guidance for these locations. During the course of this study, ALDOT developed an Intersection Control Evaluation (ICE) policy, which to some extent addresses the last objective. This study reviewed the literature, estimated calibration factors for safety performance functions for three-leg and four-leg intersections of this type, reviewed geometric and traffic control features that may improve safety performance, and examined differences in safety performance among several selected intersections in Alabama. A review of the literature and current practice found many treatments with respect to geometrics and traffic control devices that can be applied to the conventional form of this type of intersection with the goal of reducing crash frequency and crash severity. An analysis involving 47 three-leg and 65 four-leg intersections in the state yielded recommend calibration factors for the relevant safety performance functions. Several selected sites with atypical design and traffic control treatments were reviewed. Finally, a traffic conflict study across several intersections with conventional and unconventional treatments was conducted to further identify the types of conflicts that contribute to poor safety performance
