A Sensitivity Analysis of Cowan's M3 Capacity Model Applied to Roundabouts

Luis Vasconcelos, Ana B. Silva, and Álvaro Seco


Roundabout, capacity


Capacity models based on gap acceptance theory are widely used in priority intersections and roundabout capacity analysis. These models are based on the statistical distribution of major vehicle headways. In this field, Cowan’s M3 distribution is usually recognized as the most adequate, but estimating its parameters is not trivial. In this paper, the main estimation methods are reviewed and a new method is proposed. The new method is used on the development of a calibrated relation between parameters, using field data collected in portuguese roads and roundabouts. The paper also addresses the importance of each input variable and parameter in the resulting capacity model, through a sensitivity analyses.

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