The Theory Model of Urban Roundabouts' Capacity

In order to take effective control and management measures to urban roundabouts, must make accurate calculation to the traffic capacity of urban roundabouts. The theoretical models of roundabouts'capacity are closely connected with the road and traffic flow's conditions. This paper analyzed from the road and traffic characteristic of urban roundabouts, based on the gap-acceptance theory, utilized probability method, from the hypothesis that the headway of the roundabout obeys the Erlang distribution, deduced the general the model of the urban roundabouts' capacity. The accuracy of this model was verified by real traffic test result, and the effects of the road and traffic properties on the capacity of urban roundabouts are discussed. The new model is more equitable and more practical for planning and designing of the roundabouts than current formula.