Roundabout Feasibility Study for West Memphis

Crone, John V.; Garcia, Carolyne; Loewer, Otto · 2007 · ROSA P / University Transportation Centers Program (U.S.)

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Summary

This study addresses the feasibility of implementing roundabouts at the I-40/I-55 and State Highway 77 intersection in West Memphis, Arkansas, to improve safety, traffic efficiency, and aesthetics. The intersection serves as a critical gateway to the state and suffers from high collision rates, congestion, and visual disarray, exacerbated by increasing railroad traffic that causes significant vehicle queuing. The project was motivated by the need to resolve conflicts between community economic development goals and technical transportation constraints, while also creating a replicable model for community-based transportation planning in rural-to-urbanizing areas. The research was conducted in two phases. Phase 1 involved a multidisciplinary team of civil engineering and landscape architecture students, alongside the Arkansas Highway and Transportation Department (AHTD) and local stakeholders, to evaluate design alternatives. Phase 2 focused on developing a participatory planning model. The technical analysis utilized data from the AHTD and a preliminary railroad overpass study by Parsons Engineering Firm, which recommended bridging the railroad tracks to mitigate train-induced delays. The team applied Federal Highway Administration design guidelines to create geometric layouts for multilane roundabouts at two potential locations relative to the rail crossing. Performance was evaluated using forecasted 2028 traffic volumes, analyzing degree of saturation, delay, and queue length. The findings highlight the theoretical benefits of roundabouts, including up to a 90% reduction in fatalities, a 76% reduction in injury crashes, and increased traffic capacity. However, the specific feasibility analysis for the West Memphis site revealed significant operational challenges. The design alternative for Intersection 1 (east of the rail line) experienced a critical delay of 373 seconds during the PM peak hour, with a queue length of 307 vehicle hours on the westbound approach. The study noted that while roundabouts improve safety compared to signalized intersections, they do not fully resolve congestion caused by long, idle trains blocking crossings. The preferred geometric solution involved having the railroad cross the intersection legs rather than penetrating the roundabout, though this did not eliminate queuing issues associated with projected increases in freight train frequency. The significance of this work lies in its dual contribution to transportation engineering and community planning. Technically, it demonstrates the complexities of integrating roundabouts with heavy rail infrastructure and interstate ramps, emphasizing the need for careful geometric design and capacity analysis. Strategically, the project establishes a "participatory model" for engaging students and community stakeholders in transportation planning. This approach aims to bridge the gap between technical regulatory constraints and community desires for aesthetic and economic improvement, providing a framework for other communities in the Arkansas Delta and beyond to pursue similar infrastructure enhancements.

Key finding

Roundabout designs at the West Memphis intersection demonstrated potential for significant safety improvements and increased traffic capacity, although specific layouts required mitigation for delays caused by adjacent railroad crossings.

Methodology

modeling

Provenance

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Topics

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• intersection design