A deficiency of roundabouts in urban areas arises when lengthy delays occur on one or more legs of the roundabout. This event occurs when the entering and circulating volumes are not evenly spread, typically during the peak periods when traffic flows have a predominantly directional characteristic. These conditions develop a negative public opinion about roundabouts that ignore the safety and capacity benefits that roundabouts provided for the majority of the day. Introducing traffic signal control to a roundabout is a technique that can be used to overcome problems associated with uneven traffic flows during peak periods. However, the form of signal control, its operation details and its impact on all road users all need to be considered before it can be adopted for application at a roundabout. A conceptual analysis model has been developed by Akcelik and Associates Pty Ltd (May 2001) to analysis roundabouts with metering signals. This model was tested using a range of data to verify its operation and to test its robustness. Using the results obtained from the model, a set of guiding principles was developed for the appropriate use of metering signals at roundabouts.
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