Lane-Based Micro-Analytical Model of a Roundabout Corridor

This paper describes a lane-based micro-analytical network model and demonstrates it using a detailed example of staggered-T roundabouts. The model has been developed recently and implemented in the SIDRA INTERSECTION software Version 6. Two fundamental elements of the model are (i) determining the backward spread of congestion as queues on downstream lanes block upstream lanes, and (ii) applying capacity constraint to oversaturated upstream lanes for determining exit flow rates, 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. Estimation of lane capacities, lane flows and lane queues for downstream and upstream approaches is essential for reliable modelling of network performance since these parameters are highly interdependent. The new lane-based analytical network model differs from traditional network models which rely on modelling of "approaches" or "links" based on aggregation (and therefore losing details) of individual lane condition.