Modelling Queue Spillback and Nearby Signal Effects in a Roundabout Corridor

Aerial photograph of road


This paper discusses two aspects of modelling roundabout corridors: (i) a lane-based model of queue spillback, i.e. blockage of upstream lanes by queues formed in downstream lanes and the resulting capacity reduction in those lanes, and (ii) a model of the effect of upstream signals on the capacity and performance of a roundabout located downstream of a signalized intersection. A roundabout corridor example is provided to discuss both aspects. When capacity reduction of upstream lanes due to queue spillback results in oversaturated conditions, it is necessary to apply capacity constraint in determining exit flow rates of oversaturated upstream lanes, thus limiting the flows entering downstream lanes. These two elements are highly interactive with opposing effects. Establishing the relationship between upstream and downstream lane flow rates and identifying lane change implications are also important aspects of the model. The paper also discusses potential effects of nearby signalized intersections on a roundabout corridor. These include lane blockage by queues formed at downstream signals and bunching of vehicles arriving from upstream signals.


AKÇELIK, R. (2014). Modelling Queue Spillback and Nearby Signal Effects in a Roundabout Corridor. Paper presented at the TRB 4th International Roundabout Conference, Seattle, WA, USA, Apr 2014.