Operation Improvements at Traffic Circles

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CAIT project no.: 129 RU6544

Fiscal Year: 2002/2003

Status: Final

Rutgers-CAIT Author(s): Kaan Ozbay

External Author(s): Rober Sasor

Sponsor(s): NJDOT


Traffic circles have been used in the United States since 1905. However, their use has been limited since the 1950’s due to the realization that they worked neither efficiently nor safely (NCHRP- WEB Page). Recently, there has been increasing interest in improving existing traffic circles to address these safety and efficiency problems. Several states, including New Jersey, are in the process of exploring effective operational alternatives for enhancing safety and efficiency of these traffic circles built in the early parts of the 20th Century. Many existing traffic circles in New Jersey, that were designed to handle lesser
traffic volumes than today’s volumes, fall under this category of traffic circles that need to be improved since they are faced with increasing congestion and accident problems. Although replacement of these traffic circles appears to be a viable option time and money needed for the construction of alternative solutions can be prohibitive especially in this atmosphere of diminishing resources for any kind of major investment due to the budget problems of the State. The next best option appears to be the implementation of operational alternatives that can extend the life of these circles until they can be rebuilt in the next 5 to 20 years. To study operational alternatives, traffic simulation computer software that can accurately model the geometry & traffic on circles, and provide animated graphics of traffic movements is needed. The major goal of this computer based analysis of the traffic circles as proposed in this study is to accurately evaluate the effectiveness of various traffic engineering measures such as ramp metering, sign and line treatments, reconstructing or adding lanes, in terms of improve traffic flow or safety at a specific circle.