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Nathan Belz Dissertation on Roundabouts
- By TRC Staff
Nathan Belz is a graduate research assistant at the Transportation Research Center and will receive his Ph.D. through the College of Engineering and Mathematical sciences. Belz presented his dissertation work focused on planning and traffic operations modeling of roundabouts on August 2nd. Roundabouts are an emerging type of intersection design in the United States. As such, the lack of exposure and driver confusion affect traffic operations and public acceptance. Much of the knowledge of roundabout operations has also been based on data collected internationally where roundabouts are more common. Belz saw a need to address these gaps in order to better design, plan, and implement roundabouts in the United States.
Using video-based real-world data of traffic operations, Belz identified types of driver behavior that are inconsistent with the traffic theories on which existing roundabout models are based. These behaviors (termed priority taking, abstaining,and surrendering) relate to incorrect negotiations of circulating and entering drivers which directly affect how efficiently a roundabout is able to operate (refer to the figure below for an example). His research advances the knowledge of how non-geometric factors such as prevailing conditions and driver familiarity impact driver behavior. This data further informed a new roundabout model developed by Belz using a cellular automata approach where agents (vehicles) move from one cell to another over units of time. The model provides a quantitative assessment of how these incorrect negotiations impact roundabout performance measures such as capacity, queue length, and delay. In addition, Belz applied spatial analysis techniques to evaluate roundabout implementation trends in northern New England and examine factors that affect where technically feasible roundabouts are and are not being built.
(Above) An example of priority taking where an entering vehicle (a) approaches the roundabout entry, (b) enters into the roundabout in front of a circulating vehicle, and (c) causes that circulating vehicles to either stop or slow considerably in order to avoid collision.
Also during his time at UVM, Belz contributed to and published research on transportation applications of Geographic Information Systems, transit planning and ridesharing in Vermont, livability in small-urban and rural communities, second-by-second driver behavior using in-vehicle instrumentation, and ridesharing in Vermont. Belz defended his dissertation in early August and is moving on to a tenure-track faculty position at the University of Alaska – Fairbanks. He will continue his work on roundabouts and also focus on transportation issues in rural and cold climates.
You can read about Belz's dissertation at: http://www.uvm.edu/~transctr/pdf/Abstract-belz.pdf