Does gap acceptance theory adequately predict the capacity of a roundabout?

The traffic capacity and delay at roundabouts are important measures of an intersection's performance. The capacity of a roundabout is affected by drivers'behaviour and the driving code. This paper reviews the more important methods of estimating the capacity of a roundabout and discussed the development of a capacity model assuming the headways have a dichotomised distribution proposed by Cowan. The ability of the various models to predict the capacity of a particular single lane roundabout is also discussed.