Refining Roundabouts – The Next Five Years

March 15, 2006

Modern roundabouts are being implemented at an increasing rate in the United States. The limited state of practice has resulted in numerous studies assessing the performance of roundabouts in the United States. Many of these studies are being conducted as part of the National Cooperative Highway Research Program (NCHRP), a program developed by the Transportation Research Board to develop near-term, practical solutions to problems facing transportation agencies.

As the prime contractor of NCHRP 3-65, Applying Roundabouts in the United States, KAI has led the development of operational and safety models, design criteria and guidance, and educational materials. As more roundabouts are built, there will be more data, which can be used to better quantify operations and safety influences, such as, pedestrian and bicycle activity, sight distance, either atypical or non-standard geometry, and speed environments. These research materials will provide policy makers with tools to compare and contrast roundabouts against traditional intersection treatments. It is anticipated that as more modern roundabouts are constructed the cost effectiveness will be more formally quantified.

Optimizing operations and safety requires careful attention to the design. Design guidance is currently provided in the Federal Highway Administration’s (FHWA) publication, Roundabouts: An Information Guide, and by the FHWA’s latest Manual on Uniform Traffic Control Device signing and striping recommendations, to which KAI made significant contribution. Practitioners can anticipate multi-lane roundabout design guidance to improve over the next five years as more data becomes available with the increased construction of complex sites.

NCHRP 3-78, Crossing Treatments at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities, will focus on access and wayfinding for pedestrians with vision impairments, while also evaluating pedestrian treatments currently recommended at roundabouts. Examples of considered treatments are: flashing beacons, audio queues and noise surfaces, traffic calming beyond the exit, signals, and raised crossings.

The industry can expect to see some major development in U.S. roundabouts tools throughout the next decade. The upcoming research studies will result in updates to the Highway Capacity Manual (HCM), the American Association of State Highway and Transportation Officials’ (AASHTO) Green Book, and the U.S. Access Board’s ADA accessibility guidelines. As the industry develops in this arena, KAI continues to focus on research, training, and peer reviews to ensure the consistency in roundabout design.

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