The evaluation of advanced Intelligent
Transportation Systems, and particularly those
which involve real–time traffic management, requires
a network-wide assessment of their impact as
opposed to an isolated analysis of key intersections. To
support such assessments, an integrated simulation environment
that allows the use ...»»»»
The evaluation of advanced Intelligent
Transportation Systems, and particularly those
which involve real–time traffic management, requires
a network-wide assessment of their impact as
opposed to an isolated analysis of key intersections. To
support such assessments, an integrated simulation environment
that allows the use of different modeling levels
(e.g., macro-meso-micro) offers undeniable advantages.
One of the advantages is that traffic assignment results produced
by any type of network loading modeling can be stored
and reused for another simulation run. But even in an integrated
environment with separate models, deciding between
microscopic or mesoscopic was until recently a necessary and
difficult choice. On the one hand, microscopic traffic simulation
models emulate the dynamics of individual vehicles in a detailed
network representation based on car-following, lane changing,
and gap acceptance models. They also account explicitly for traffic
control. As such, they are very appropriate for operational analysis
due to the detail of information provided by the simulator. However, they have a significant calibration and computational cost. On the other hand, 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; for instance, de-tector measurements or instantaneous emissions. Some outputs, such as the number of start-stops or the exact location of con-gestion within a section elude even the most detailed mesoscopic simulators. This analysis gives rise to the need to combine meso and micro approaches into new concurrent hybrid traffic simulators where very large-scale networks are modeled mesoscopically and areas of complex interactions benefit from the finer detail of microscopic simulation. Combining an event-based mesoscopic model with a more detailed, time-sliced microsimulator raises consistency problems within the network rep-resentation and the meso-micro-meso transitions.^^^^
