BACKGROUND 

As the number and prevalence of intersection types and configurations increase, it has become more challenging for practitioners to quantify the safety effects of constructing these designs. Currently the American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM) provides safety performance functions for a few conventional intersections based on empirical research, but any deviation from the basic assumptions in the HSM requires the application of one or more crash modification factors (CMFs). Although there are a high number of CMFs from various sources, some apply to alternative intersection forms; fewer apply to complex traditional intersections that diverge from the basic intersections in the HSM. Intersection control evaluation policies and efforts typically promote the consideration of alternative intersections not covered in the HSM, which has limited the ability of practitioners to compare the safety performance of these alternative intersections to conventional designs. 

One element that is common to all at-grade intersections is the conflict point, the location where two or more paths may cross. Previous research has demonstrated relationships between the number of conflict points at an intersection and the number of resulting crashes over a given time period. Similarly, crash severity can be roughly correlated to conflict type, angle, and speed. Alternative intersections have been touted as an improvement in safety over conventional forms due to a reduction in total conflict points, conflict point proximity, and speed. There is a need for a new methodology to assess a variety of intersections' safety performance from the perspective of conflict point type. 

OBJECTIVES 

The objectives of this research are to

• Develop a quantifiable method to uniformly identify and describe at-grade intersection conflict point types under different contexts; and
• Develop and validate a predictive methodology, using intersection conflict point types to predict multimodal crash frequency and severity, to supplement those in the HSM Part C models.