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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

Evaluation of Cost‐effective Alternative Designs for Rural Expressway Intersections

High-speed expressways functionally operate like freeways but have at-grade intersections that provide critical access to communities via minor roadways. These intersections provide key economic entry points to jobs and economic development and serve as lifelines for rural communities. They also provide ingress and egress for emergency vehicles and serve as evacuation routes in cases of natural disaster. As planning, design, operational and/or safety concerns arise at these at-grade intersections a typical response from concerned agencies can include either closure of such intersections leading to inequitable adverse economic and other impacts on the surrounding communities, install warning signs, or explore the construction of high-cost grade-separated interchanges. This research proposes to conduct an assessment of the role that a cost-effective alternative design, known as a Restricted Crossing U-turn (R-CUT) or J-turn intersection, can play in solving access problems on high-speed expressways in the States of California and Florida. In discussions with key stakeholders (San Luis Obispo Council of Governments (SLOCOG), Caltrans, and Florida Department of Transportation (FDOT)) investigators have identified the reasons why these intersection treatments are rarely considered in these large states. Chief among them is the reluctance to divert drivers off the shortest path and the novelty of the design. This collaborative proposal by Cal Poly SLO and University of South Florida (USF) is developed with the help and support from SLOCOG, Caltrans, and FDOT to help address these issues so that innovative intersection infrastructure design (i.e., R-CUT) are included among the alternatives considered during the Intersection Control Evaluation (ICE) process. The stakeholders noted the need for evidence of the effectiveness of these treatments to realize the potential cost-savings and access improvements. The effectiveness of the J-turn design will be demonstrated to stakeholders using i) surrogate safety and operational measures obtained through conflict analysis of traffic simulation data; and ii) Empirical Bayes (EB) before-after analysis. Both these sets of evaluations are critically needed before R-CUT designs are routinely considered by two of the largest DOTs in the U.S. Simulation models will not only provide the data for surrogate safety/operational measures but can also help stakeholders and the general public visualize the functioning of the intersection treatment; thereby supporting outreach, tech transfer, and stakeholder decision-making for this research. San Luis Obispo Council of Governments is supporting the work through matching funds from the State Transportation Partnership Program.