Roundabouts and Access Management
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Roundabouts and Access Management FDOT Project BDK77 977‐22 Final Report March 2014 Prepared for: Florida Department of Transportation 605 Suwannee Street, MS 19 Tallahassee, FL 32399 Project Manager: Gina Bonyani Systems Planning Office Prepared by: Principal Investigator Dr. Ruth L. Steiner Department of Urban & Regional Planning University of Florida 431 Architecture Building Gainesville, FL 32611 Dr. Scott Washburn, Dr. Lily Elefteriadou Engineering School of Sustainable Infrastructure and the Environment University of Florida 365 Weil Hall Gainesville, FL 32611 Dr. Albert Gan Department of Civil and Environmental Engineering Florida International University 10555 West Flagler Street, EC 3603 Miami, FL 33174 Disclaimer The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the State of Florida Department of Transportation. Roundabouts and Access Management Page ii Metric Conversion Table SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL LENGTH in. inches 25.4 millimeters mm ft. feet 0.305metersm yd. yards 0.914 meters m mi miles 1.61 kilometers km Roundabouts and Access Management Page iii Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle 5. Report Date Roundabouts and Access Management March 2014 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Ruth L. Steiner, Scott Washburn, Lily Elefteriadou, Albert Gan, Priyanka Alluri, Dimitra Michalaka, Ruoying Xu, Shanty Rachmat, Benjamin Lytle, Amy Cavaretta 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Department of Urban and Regional Planning University of Florida 11. Contract or Grant No. P.O. Box 115706 BDK77‐977‐22 Gainesville, FL 32611‐5706 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Florida Department of Transportation Final Report 605 Suwannee Street, MS 30 September 2012 – March 2014 Tallahassee, FL 32399 14. Sponsoring Agency Code 15. Supplementary Notes Gina Bonyani, FDOT Project Manager 16. Abstract Transportation engineers and planners are becoming more interested in using roundabouts to address access management and safety concerns in the transportation system. While roundabouts are being used increasingly in a variety of contexts, existing research does not provide detailed guidance on how to evaluate the use of roundabouts as a form of access management. This Florida Department of Transportation (FDOT) research project has three primary components: a review and assessment of national and state guidance related to roundabouts and access management, a safety analysis of all 283 roundabouts in Florida, and an operational analysis of selected roundabouts. Literature related to safety, access management, and multimodal transportation (especially for bicyclists and pedestrians, and roadway capacity associated with the use of roundabouts) is reviewed, and gaps in knowledge regarding the use of roundabouts are identified, particularly as they apply to safety, access, and capacity. One of the findings of the literature review is that little research has been completed on access management near roundabouts. A review of national and state guidance identifies major studies including NCHRP 672 and guidance in Kansas, Wisconsin and Virginia that recommend intersection and driveway spacing similar to that recommended for un‐ signalized intersections. The safety and operational analysis identifies four areas of concern: corner clearance, including stopping site distance (SSD) and intersection sight distance (ISD); the need for guidance on the functional area near roundabouts including driveway and intersection spacing, and the use of medians; access to major activity centers; and safety of vulnerable road users, especially bicyclists and pedestrians. The operational analysis confirms previous research that shows that roundabouts are similar to un‐signalized intersections, but the differences may influence the operations and safety within the functional area of the roundabout. An assessment of the primary FDOT utilized software tools focuses on the current suitability of these software tools to assist practitioners in assessing the suitability of incorporating roundabouts into existing and proposed roadway configurations. Recommendations are made for additional national research on guidance on driveway and intersection spacing, medians, and SSD and ISD in the different contexts in which roundabouts are installed. Changes to the FDOT’s Access Management Tools, Median Handbook and Driveway Information Guide are also recommended along with the development of Florida‐specific parameters for capacity and safety analysis. Modifications to roundabout design guidelines and handbooks for access management will lead to safer, more effective, and ultimately, better performing roundabouts for all users of Florida’s transportation system and throughout the United States. 17. Key Words: Roundabout, access management, safety, 18. Distribution Statement capacity, operational analysis No restrictions. 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of 22. Price Unclassified. Unclassified. Pages 177 Form DOT F 1700.7 (8‐72) Reproduction of completed page authorized Roundabouts and Access Management Page iv Acknowledgements The project team would like to thank Gina Bonyani and Gary Sokolow, of the Florida Department of Transportation (FDOT) Systems Planning Office, for their assistance in understanding the scope of the project and for their feedback. The research team wishes to acknowledge the efforts of national experts on roundabouts, including Andrea Bill, Phil Demosthenes, Patrick Flemming, Hillary Isebrands, Mark Johnson, Howard McCullough, Lee Rodegerdts, Eugene Russell, Jeff Shaw, Ken Sides, Michael Wallwork, and Brian Walsh, for their willingness to participate in this research in a variety of ways, including discussing design, safety, policy, and other topics related to access management near roundabouts, providing time in meetings of the ITE Roundabouts and the Transportation Research Board (TRB) Roundabouts Committee, and to reviewing the drafts of this final report. Roundabouts and Access Management Page v Executive Summary Summary of Final Report, BDK77 977‐22 March 2014 Background Over the last twenty years, engineers and planners have become increasingly interested in the use of roundabouts because they offer several advantages over other traffic controls; they may cost less to install, have greater safety potential by reducing the number of conflict points, can accommodate a series of U‐ turns and left‐turn lanes and reduce delay in a corridor, and, may have lower operations and maintenance costs. Florida has recently begun to encourage the use of roundabouts on the state highway system and is systematically updating its guidance documents (e.g., Plans Preparation Manual, Intersection Design Manual, and Manual on Uniform Traffic Studies) but needs guidance on what to include in the Median Handbook, and Driveway Information Guide and other access management documents. Objectives The purpose of this study is to understand previous research and state and national guidance on roundabouts and access management, and to conduct empirical research on the safety and operation of roundabouts in Florida. Advice on implementing roundabouts and access management into state guidance documents will be provided. The research objectives were achieved by completing the following tasks: 1. Literature and background review of national and state guidance; 2. Safety analysis of all 283 roundabouts in Florida; 3. Operational analysis of thirteen selected roundabout sites in Florida; and 4. Software tools review for roundabout simulation and evaluation. Findings and Conclusions The review of national guidance on roundabout and access management shows that only five federal access management reports refer to roundabouts: AASHTO Green Book, NCHRP Report 672 – Roundabouts: An Informational Guide, Second Edition, NCHRP Report 572 – Roundabouts in the United States, NCHRP Report 674 – Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities, and NCHRP Synthesis 264 – Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities. NCHRP Report 672, which is the most relevant to this report, refers to the access management in the context of roundabouts and reinforces the idea that many of the access management principles that apply to conventional intersections can be applied to roundabouts. State guidance on roundabouts and access management provides varying levels of specificity, with most states adopting national guidance from NCHRP Report 672 – Roundabouts, An Informational Guide; a few states provide state‐specific parameters and guidance. While several states adopt local parameters for roundabouts, only three states – Wisconsin, Virginia, and Kansas – address the use of access management within the broader context of the design of roundabouts. The safety and operational analyses of existing roundabouts in Florida identify three areas of concern about access management near roundabouts: (1) conflicts within the functional area of roundabouts; (2) safety of vulnerable road users, including pedestrians and bicyclists; and (3) roundabouts that provide direct access to activity centers. Of a total of 2,941 crashes that occurred from 2007 – 2011 within 500