Capacity and Performance Analysis of Roundabout Metering Signals

This paper describes a method for the analysis of capacity and performance of roundabouts operating with metering signals. When low capacity conditions occur during peak demand flow periods, for example due to unbalanced flow patterns, the use of metering signals is a cost-effective measure to avoid the need for a fully-signalized intersection treatment. Roundabout metering signals are often installed on selected roundabout approaches and used on a part-time bases since they are required only when heavy demand conditions occur during peak periods. Metering signals have been used in Australia, the United Kingdom and the United States to alleviate the problem of excessive delay and queuing by creating gaps in the circulating stream. The Australian roundabout and traffic signal guides acknowledge the problem and discuss the use of metering signals. The basic principles of the operation of roundabout metering signals are explained. Case studies of various roundabouts where metering signals were used, or considered for use, have been presented in previous papers by the author. This paper presents the results of analysis of one of these case studies when operating with metering signals.