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Investigating Implementation Potentials of Turbo Roundabouts in Nevada
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2024-03-01
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[PDF-7.05 MB]
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Edition:Final Report, August 2021 to March 2024
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Abstract:Turbo Roundabouts – an emergent and “new” concept in the design of roundabouts – has the potential to address the limitations experienced with the adoption of multi-lane (2x2) roundabouts. The turbo roundabout can effectively guide drivers within the roundabout by restricting lane-changing and reducing lane-change-related conflicts, which are common in multi-lane roundabouts. Within the U.S., the adoption/use of turbo roundabouts has been limited, and few recent applications. The overall goal of this project was to develop guidelines for the Nevada DOT that would assist with providing performance measures and aid potential installations of turbo roundabouts. This study performed microsimulation and driving simulator-based evaluations of basic and egg turbo roundabout designs, two popular versions of the turbo roundabout. Results showed that the theoretical capacities are always higher than the observed and microsimulation capacities, and there is some difference between the simulated and practical capacities. Surrogate safety analysis showed that a basic turbo-roundabout had 18-30% fewer traffic conflicts than a traditional two-lane roundabout for different traffic compositions. A set of driving simulator scenarios was executed to investigate drivers' navigational behavior(s) within turbo roundabouts. Participant drivers’ performance was evaluated on three roundabout designs – a basic turbo, an egg turbo, and a two-lane roundabout. Results showed the critical gaps as 4.2 secs, 6.1 secs, and 3.9 secs for the basic turbo, egg turbo, and traditional two-lane roundabouts, respectively. Additionally, participant drivers’ speed profiles depicted similar patterns among roundabout designs, where the speeds were relatively lower for the basic turbo roundabout than the two-lane roundabout along the approach legs. As a part of the project, a multi-criteria intersection control evaluation (ICE) tool was also developed and can be used to evaluate and select between roundabout designs. Lastly, a pilot field demonstration plan was developed to facilitate turbo roundabout pilot deployment in Nevada.
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