Examining the Safety Performance of Urban/Suburban Arterials and Freeway Segments in Consideration of Roadway Geometry and Traffic Control.

摘要

With the sprawling of major cities and creation of suburban areas, one problem that state agencies face is the increasing congestion in suburban arterials coupled with the safety risks posed by increasing traffic volumes at traditional intersections along arterials. In the early 1960s, a new intersection design was developed and installed in the state of Michigan, where left turns at intersections were replaced by median U-turn lanes (MUTs). This study focuses on the safety performance of corridors where median U-turns (MUTs) are present along urban and suburban boulevards. The analysis is performed in two stages; first models were developed separately for assessing the safety performance, through the examination of crash frequency and type, across individual MUTs, at intersections, and along segments on which MUTs are located. Subsequently, an aggregate-level analysis is conducted to assess the safety performance of specific intersections/MUT combinations. The second stage focused on developing models for examination of sites spanning each side of an intersection including upstream and downstream MUTs. These sites were compared to sample sites with allowed traditional left turn movements. Ultimately, the results provide guidance to agencies considering the installation of such alternative intersections.;Additionally, safety risks are present during work zone projects along freeways, which are essential facilities for providing mobility. The presence of a work zone generally results in both mobility and safety impacts to road users. Minimizing the adverse impacts associated with work zones has become a priority for road agencies. This study will estimate SPFs that consider freeway geometry and traffic conditions, as well as the effects of various temporary traffic control strategies such as lane shifts, shoulder closures, and lane closures. Crash modification factors were developed for work zone duration and length. Additionally, the study results provide insight on the safety impacts associated with each of the four types of lane closures.