Accelerating Roundabout Implementation in the United States - Volume I of VII: Evaluation of Rectangular Rapid-Flashing Beacons (RRFB) at Multilane Roundabouts

Schroeder, Bastian J.; Salamati, Katy; Rouphail, Nagui M.; Findley, Daniel; Hunter, Elizabeth; Phillips, Brian D.; Barlow, Janet; Rodegerdts, Lee A. · 2015 · ROSA P / United States. Department of Transportation. Federal Highway Administration. Office of Safety

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Summary

This study evaluates the effectiveness of Rectangular Rapid-Flashing Beacons (RRFB) in enhancing pedestrian accessibility at multilane roundabouts in the United States. Motivated by the rapid increase in roundabout installations and ongoing concerns regarding safety for visually impaired pedestrians, the research addresses whether RRFBs can serve as a viable, lower-cost alternative to pedestrian-actuated signals. Specifically, the project investigates if RRFBs improve driver yielding compliance, how geometric configurations influence accessibility, and whether these treatments provide sufficient crossing opportunities for blind pedestrians. The methodology involved an "Accessibility Audit" conducted at 12 approaches across seven multilane roundabouts in five states. The study analyzed 24 legs (entry and exit) using five primary data collection methods: a crossing indicator study with blind participants accompanied by Certified Orientation and Mobility Specialists (COMS), a naturalistic driver yielding study, a free-flow speed assessment, a geometric audit, and a 12-hour traffic volume assessment. Key performance measures included the percentage of estimated interventions (instances where a COMS would have physically restrained a pedestrian to avoid collision), pedestrian delay, free-flow vehicle speeds, and driver yielding rates. Results indicated that RRFB-equipped multilane roundabouts can be accessible, but performance varies significantly based on site-specific factors. There were strong correlations between traffic flow characteristics, geometric design, and accessibility outcomes. Specifically, higher vehicle volumes and faster free-flow speeds were associated with increased intervention rates and reduced yielding compliance. Geometric configurations also played a critical role; sites with tighter curvature generally exhibited lower speeds and better accessibility, while wider radii allowed for higher speeds that hindered safe crossing decisions. The study found that while RRFBs improved yielding compared to untreated crossings, the increase in yielding alone did not guarantee accessibility for blind pedestrians, as geometric obstructions and high speeds continued to limit safe gap availability. The significance of this research lies in its contribution to the Federal Highway Administration’s goal of accelerating roundabout implementation by providing empirical data on accessibility treatments. The findings suggest that RRFBs are a promising tool for improving driver behavior but must be implemented alongside careful geometric design to ensure they are effective for visually impaired users. The study supports the notion that accessibility is not solely dependent on traffic control devices but is heavily influenced by the interplay of geometry, speed, and driver behavior, offering practitioners specific insights for designing safer, more inclusive roundabouts.

Key finding

RRFB-equipped multilane roundabouts can be accessible, but accessibility is strongly influenced by roundabout geometry, vehicle speeds, and driver yielding behavior.

Methodology

naturalistic

Sample size: 7

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• intersection design
• perceptual countermeasures
• rail grade crossings