A Comparison of Roundabout Capacity Models

Luís Vasconcelos, Álvaro Seco, Ana Bastos Silva, Tiago Abreu, and João P. Silva


Roundabout, Gap-acceptance, Capacity


In the present study four roundabout capacity models – Siegloch, Cowan M3-1L, Cowan M3-2L and TRL – are presented and compared against microscopic simulation results. The evaluation framework is centered mostly on the characteristics of the entering and circulating traffic and it is shown that the more popular models – TRL and Siegloch, are unable to generate consistent capacity estimates for the whole range of conflicting flows. The models based on Cowan M3 headway distribution are more robust but still they aren’t sensible to differences in the vehicles destinations, both in the entry and in the circulating traffic. This aspect is also poorly handled by the microscopic simulation model.

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