AROUND - Improving Capacity And Emission Models of Roundabouts

Publications

Driver Behavior Characterization in Roundabout Crossings

Publication . Silva, Ana Bastos; Santos, Sílvia; Vasconcelos, Luís; Seco, Álvaro; Silva, João Pedro

Roundabouts are widely accepted for their safety, capacity and environmental advantages. Although it can be easily recognized that the driver behavior is mostly related with the roundabout geometry. This paper presents a detailed characterization of the driver behavior while crossing three consecutive double-lane roundabouts in an arterial road. Driver behavior was described in three main levels: i) speed profiles; ii) lateral acceleration profiles; iii) roundabout geometry. It is shown that roundabouts can substantially reduce speed in the negotiation zone. The entry speed and influence zone depends on the desired speed in the upstream sections and on the roundabout geometric characteristics.

2014Journal article

Open access

Estimating the parameters of Cowan’s M3 headway distribution for roundabout capacity analyses

Publication . Vasconcelos, Luís; Silva, Ana Bastos; Seco, Álvaro; Silva, João

Capacity models based on the gap acceptance theory are widely used in unsignalised intersections and roundabout capacity analysis. !ese models are based on the statistical distribution of major vehicle headways. In this "eld, Cowan’s M3 distribution is usually recognized as the most adequate, but the estimation of its parameters is not trivial. In this paper, the main estimation methods are reviewed and a new method (Simultaneous Numerical Estimation – SNE) is proposed. !e SNE method was used to develop a calibrated relation between parameters, using "eld data collected in Portuguese roads and roundabouts. It was determined that the new formula improves capacity estimates, either in one-lane or in two-lane roundabouts. !e paper also addresses the importance of each input variable and parameter in the resulting capacity model, through a sensitivity analyses.

2012-12-13Journal article

Open access