Time headway at roundabouts, as one of the important parameters to describe the traffic flow characteristics at roundabouts, is the key to study behavioral characteristics of drivers, delay analysis at roundabouts, safety analysis, traffic capacity calculation, etc. In this paper, according to the actual observation data at signalized roundabouts and unsignalized roundabouts, the change rules of traffic flow and time headway are obtained. Then a mixed headway distribution model is proposed. After chi-square test and data fitting, it is shown that the mixed distribution model can better describe the characteristics of headway distribution at roundabouts. This paper completes some related researches on time headway of roundabouts, which is helpful to study the operation characteristics of traffic flow at roundabouts, and is convenient for delay analysis at roundabouts and design of roundabouts.

Time headway; Roundabouts; Characteristic analysis; Mixed distribution