Safety Effectiveness and the Role of Geometric, Traffic, and Crash History–Related Factors in Converting a Stop-Controlled Intersection to a Miniroundabout
Publication: Journal of Transportation Engineering, Part A: Systems
Volume 148, Issue 10
Abstract
The focus of this paper is on evaluating the safety effectiveness of converting a stop-controlled intersection with a speed () to a miniroundabout and examining the role of influencing factors on their safety effectiveness in the United States. Crash, traffic volume, and geometry data for 25 miniroundabouts in eight states was collected to conduct before–after analysis using the empirical Bayes (EB) method. In addition, crash and traffic volume data for 723 reference intersections were gathered and used for computing the calibration factors and developing jurisdiction-specific safety performance functions (SPFs). A 19.63% and 60.55% reduction in the number of total crashes and fatal and injury (FI) crashes but an 7.72% increase in property damage only (PDO) crashes was observed when a two-way/one-way stop-controlled (TWSC/OWSC) intersection was converted to a miniroundabout. A 224.76%, 74.30%, and 282.71% increase in the number of total crashes, FI crashes, and PDO crashes was observed when an all-way stop-controlled (AWSC) intersection was converted to a miniroundabout. Converting a TWSC/OWSC intersection to a miniroundabout has better safety benefits than converting an AWSC intersection to a miniroundabout. The recommended crash modification factors (CMFs) for converting a TWSC/OWSC intersection to a miniroundabout are 0.80, 0.39, and 1.08 for total, FI, and PDO crashes. The recommended CMFs for converting an AWSC intersection to a miniroundabout are 3.25, 1.74, and 3.83 for total, FI, and PDO crashes. The number of crashes in the before period, cross-street traffic volume, speed limit at major street and cross-street, and intersection skewness have a statistically significant influence on the safety effectiveness of miniroundabouts at a 90% confidence level. These findings are useful to researchers and practitioners for conducting safety benefit analysis and making informed decisions pertaining to converting a stop-controlled intersection to a miniroundabout.
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Data Availability Statement
Some or all data, models, or code generated or used during the research are available from the authors by request.
Acknowledgments
The authors acknowledge the NCDOT for providing financial support for this project. Special thanks are extended to James H. Dunlop, Joseph E. Hummer, Carrie L. Simpson, Brian Mayhew, Lisa E. Penny, Mustansir A. Kadibhai, Curtis Bradley, and John W. Kirby for providing excellent support, guidance, and valuable inputs for successful completion of this project. The authors acknowledge the support and response from the staff of Georgia Department of Transportation (GDOT), Iowa Department of Transportation (IOWADOT), Michigan State Police, Michigan Department of Transportation (MDOT), Washtenaw County Road Commission, Minnesota Department of Transportation (MnDOT), Missouri Department of Transportation (MoDOT), NCDOT, Virginia Department of Transportation (VDOT), Washington State Department of Transportation (WSDOT), and Highway Safety Information System (HSIS) for sharing data required for this research. They also acknowledge initial efforts by V. R. Duddu and data collection efforts by other graduate students of the IDEAS Center.
Disclaimer
The contents of this paper reflect the views of the authors and not necessarily the views of the University of North Carolina at Charlotte (UNC Charlotte) or the NCDOT. The authors are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of either UNC Charlotte, NCDOT, or the Federal Highway Administration (FHWA) at the time of publication. This report does not constitute a standard, specification, or regulation.
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Published In
Journal of Transportation Engineering, Part A: Systems
Volume 148 • Issue 10 • October 2022
Copyright
© 2022 American Society of Civil Engineers.
History
Received: Nov 24, 2021
Accepted: May 12, 2022
Published online: Jul 29, 2022
Published in print: Oct 1, 2022
Discussion open until: Dec 29, 2022
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