A rural expressway is a high-speed, multi-lane, divided highway with partial access control which may consist of both at-grade intersections and grade separated interchanges. Many State Transportation Agencies (STAs) areconverting rural two-lane undivided highways into expressways for improved safety and mobility; however, collisions at two-way stop-controlled (TWSC) expressway intersections (particularly far-side right-angle crashes) are reducing the safety benefits that should be achieved through conversion. When the safety performance of these intersections deteriorates, the improvement path typically begins with several signing, marking, or lighting improvements, followed by signalization, and could ultimately result in grade separation (although the extremely high cost of right-of-way makes it unlikely in many cases). Signals aren't always effective at improving safety and hamper the mobility expressways are meant to provide. Interchanges are not economically feasible at all problematic intersections and can take many years to develop; therefore, there is a need for more design options at TWSC rural expressway intersections. Some STAs have experimented with innovative rural expressway intersection safety treatments which are not currently included as design options within national guides. Therefore,NCHRP 15-30, Median Intersection Design for Rural High-Speed Divided Highways was commissioned to recommend revisions to AASHTO's A Policy on Geometric Design of Highways and Streets (Green Book) and the Manual on Uniform Traffic Control Devices (MUTCD) regarding intersection design for rural expressways. The project tasks included summarizing the existing design guidance for rural expressway intersections within these national guides, documenting STA experience with innovative rural expressway intersection safety treatments, and recommending revisions to the Green Book and theMUTCD. The results of this work are summarized in this paper, with a focus on the suggested Green Book and MUTCD modifications.
Samenvatting