Evaluating urban intersections: a comparative study of roundabouts versus protected U-turns—which is better?
DOI:
https://doi.org/10.55329/jbwz1736Keywords:
geometric design, microsimulation, protected U-turn, PTV VISSIM, roundaboutAbstract
Effective urban traffic management is a significant challenge in rapidly urbanizing areas with increased vehicular usage, impacting both congestion and safety. Busy cities, like many urban centers, face these issues. Roundabouts, known for their ability to reduce severe crashes, represent a traditional approach to intersection design. However, in high-traffic conditions, roundabouts can become less efficient, leading to increased congestion. Alternatively, protected U-turns, which are a relatively modern approach, are designed to handle high traffic volumes more effectively. They potentially reduce waiting times and improve overall traffic flow but may pose different safety and longitudinal challenges. This study aims to explore these complexities by analyzing the effectiveness of roundabouts and protected U-turns in the context of the unique urban landscape of the Hail City in Saudi Arabia. PTV VISSIM was used for dynamic traffic simulation, providing a realistic representation of traffic patterns in Hail City. Parameters such as vehicle queuing lengths, wait times, and overall intersection capacity are comprehensively evaluated. The simulation settings are adjusted to reflect different traffic densities and patterns, thus ensuring a thorough understanding of the performance of each intersection type under varied conditions. Additionally, various statistical analysis techniques were used to better understand the relationship between the independent and dependent variables. Results showed scenarios of high traffic volume, roundabouts led to longer vehicle queues and increased wait times. On the other hand, protected U-turns exhibited a notable capability to manage high-volume traffic, effectively reducing congestion and improving intersection throughput. This research may contribute to urban traffic management literature, offering insightful guidelines for future intersection design and traffic flow optimization in rapidly urbanizing cities.
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Author Biographies
Nawaf Alnawmasi, University of Ha'il, Saudi Arabia
Nawaf Alnawmasi is an assistant professor of Civil Engineering at the University of Hail. He obtained his undergraduate degree from the University of Hail in 2013, and his MS and doctoral degrees from the University of South Florida in 2020 (under the supervision of Professor Fred Mannering). His research interests are in the application of econometric and statistical methods to the analysis of highway safety and transportation economics and safety. He has published several research papers in the peer-reviewed journals and presented his research work in Transportation Research Board (TRB) 99th and 102nd annual meetings.
CRediT contribution: Conceptualization, Data curation, Investigation, Methodology, Software, Visualization, Writing—original draft.
Hisham Jashami, Oregon State University, the United States of America
Hisham Jashami is an Assistant Professor (Sr Res) at Oregon State University. Dr. Hisham Jashami's research has been focused on areas related to transportation safety, human factors, driving and bicycling simulators, autonomous vehicles, data visualization, and statistical methods. During the course of his academic career, Dr. Jashami worked on externally funded research from agencies including the Federal Highway Administration, the National Highway Traffic Safety Administration, the Pacific Northwest Transportation Consortium (PacTrans), and various State Departments of Transportation, e.g., Oregon DOT and Michigan DOT. This research has led to the publication of over 100 peer-reviewed journal articles, conference papers, and technical reports. He is a certified Road Safety Professional Engineer.
CRediT contribution: Conceptualization, Data curation, Investigation, Methodology, Software, Visualization, Writing—original draft.
Qiuqi Cai, HDR, Inc., the United States of America
Qiuqi Cai is a Traffic Engineer at HDR and holds a PhD from Michigan State University. Dr. Cai's research and professional expertise span areas related to transportation safety, human factors, micro simulation and statistical methods. Her contributions have included impactful work on Michigan Department of Transportation (MDOT) projects, as well as publishing and presenting research at prestigious venues such as the Transportation Research Board (TRB) Annual Meeting. She is also a certified Engineer-in-Training (EIT) with a background in civil engineering.
CRediT contribution: Conceptualization, Data curation, Investigation, Methodology, Software, Visualization, Writing—original draft.
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Copyright (c) 2025 Nawaf Alnawmasi, Hisham Jashami, Qiuqi Cai
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