Roundabouts are increasingly recognized as an intersection control strategy that can fulfill multiple performance goals related to traffic operation and safety, and meet societal goals related to sustainability, livability, complete streets, context sensitive design, economic development, and others. Some transportation agencies have recently constructed or approved the use of a series of roundabouts on an arterial rather than the traditional solution of coordinated signalized intersections. While there are anecdotal reports suggesting that functionally interdependent roundabouts on a corridor are successful in meeting performance goals, little research has been conducted to determine objectively the efficacy of this alternative as compared to signalized intersections. The performance of traffic signal systems on arterials is well researched and documented, and methods to predict their performance are well established. Performance measures for isolated roundabouts exist and safety research has consistently shown that signalized intersections have higher injury crash rates when compared to roundabouts. In contrast, qualitative and quantitative information on the performance of a set of functionally interdependent roundabouts on arterials is lacking.
The objective of this research is to provide traffic engineers, transportation planners, and other practitioners with performance measurement and evaluation methods to evaluate comprehensively the performance of functionally interdependent roundabouts on arterials, thus enabling a comparison with signalized intersections, in order to arrive at a design solution. For purposes of this research, a "series of roundabouts" shall include at least three roundabouts that function interdependently on an arterial.
The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers' current thinking described in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach in meeting the research objective. The work proposed must be divided into tasks and proposers must describe the work proposed in each task in detail. The research plan should build in appropriate checkpoints, deliverables and web-enabled teleconferences tied to the panel review and NCHRP approval of interim products. The research plan should build in appropriate deliverables that include, at a minimum: (1) a kick-off teleconference meeting of the research team and the NCHRP project panel, to be held within 1 month of the contract’s execution date; (2) a final report documenting the entire project, incorporating by reference all other specified deliverable products of the research, and presenting the research team’s recommended performance measurement methods to evaluate the performance of functionally interdependent roundabouts on arterials; (3) a PowerPoint presentation describing the project background, objective, research method, findings, and conclusions; and (4) interim reports addressing the following six topics (the number of interim reports need not correspond to the number of required topics):
(a) A literature review that, at a minimum, includes a discussion of performance measures, a summary of data that is readily available, and a summary of data gaps.
(b) Recommended performance measures and evaluation methods, including a method of calibrating estimates of corridor travel time based on a comparison of theoretical or empirical models to field sampling. NCHRP approval of recommended performance measures and evaluation methods is required before additional work items are performed.
(c) A detailed plan to conduct a field demonstration of the recommended performance measures and evaluation methods on existing arterials. At a minimum, the plan should include analyzing existing roundabout corridors as if they were a signalized system. Corridor locations that may be candidates for field demonstration sites include but are not limited to (1) Golden Road in Golden, Colorado; (2) State Route 539 in Whatcom, County, Washington; (3) State Route 179 in Coconino County, Arizona; (4) US 62 in Hamburg, New York; (5) State Route 67 in Malta, New York; (6) Ira Needles Corridor in Waterloo, Ontario, Canada; (7) La Jolla Boulevard in San Diego, California; (8) East Orange Road in Delaware County, Ohio and (9) Avon Road in Avon, Colorado. NCHRP approval of the plan is required before proceeding with subsequent work tasks.
(d) The results of implementing the plan that is described and approved in topic (c), and the evaluation data for each of the selected test corridors that presents their qualitative and quantitative performance.
(e) Recommended performance measures and evaluation methods.
(f) A detailed outline for the final report prior to its development.
STATUS: Research in progress.