Safety Evaluation of Signalized Highway Intersections Based on the Concept of Level of Safety Service

摘要

Crash analysis or conflict analysis procedures have been used for intersection safety evaluation. Both approaches need significant data from crash databases or traffic conflict observations. It might be difficult and time-consuming to obtain these data. Actually, crashes happen with certain random characteristics, and conflict analysis could involve reviewer's subjective judgments. It is useful to develop alternative ways for intersection safety evaluation. These alternative ways could be based only on existing traffic control, geometric, and roadway conditions. A feasible approach belongs to such alternatives for safety evaluation of intersections is based on the concept of safety service that an intersection can provide to traveling public, or called level of safety service. This article presents partial results from a research aiming to developing safety design procedures for highway intersections. In the article, the concept of level of safety service of signalized intersections is introduced, and corresponding models are presented. Conceptually, models under ideal conditions are based only on intersection conflict points between motorized vehicles, between motorized vehicles and nonmotorized vehicles, and between motorized vehicles and pedestrians. Variables related to traffic control, geometrical, and roadway conditions under prevailing conditions are used to adjust models under ideal conditions to obtain level of safety service under prevailing conditions.