The need to combine different traffic modelling levels for effectively tackling large-scale projects adding a hybrid meso/micro approach

The evaluation of ATMS requires a network-wide assessment of their impact as opposed to an isolated analysis of key intersections. Microscopic traffic simulation models emulate the dynamics of individual vehicles in a detailed network representation, based on car-following, lane changing, etc; include route choice models to implement dynamic traffic assignment. Microscopic models are usually appropriate for operational analysis due the detail of information provided by the simulator. However, they are data intensive and have a significant computational cost. Mesoscopic models combine simplified flow dynamics with explicit treatment of interrupted flows at intersections and allow modeling of large networks with high computational efficiency. However, the loss of realism implied by a mesoscopic model makes it necessary to emulate detailed outputs (detector measurements, instantaneous emissions). The above give rise to the need to combine meso and micro approaches into new hybrid traffic simulators where very large-scale networks are modeled mesoscopically and areas of complex interactions benefit from the finer detail of microscopic simulation.This paper presents the new system architecture implemented in Aimsun of the hybrid model with special emphasis on the consistency of the transition between the mesoscopic and the microscopic models, and vice versa and aims to demonstrate how consistency is complemented using computational results in a large-size network.