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However from its starting point as a combined simulation and assignment
model, SATURN has been extended in both directions so that it can function both
as a conventional traffic assignment model and as a pure junction simulation
model. As a “conventional” traffic assignment model (with or without simulation)
SATURN can deal with large conurbation, regional or even national models.
These may then interface with smaller localised models using the greater
precision of the junction simulation models or indeed using the DRACULA
micro-simulation with routes generated by SATURN.
With both simulation and conventional network representations SATURN provides a
wide range of assignment options such as generalised cost, all-or-nothing,
Wardrop equilibrium, Burrell multiple-route assignment (SUE) and, more recently,
demand-responsive (elastic) assignment to deal with induced traffic. All these
are founded on theoretically consistent modelling frameworks and convergent
algorithms reflecting the academic background of SATURN’s development.
At the other extreme SATURN allows for the interactive simulation and editing of
individual junctions, so that the user is able to vary parameters such as flows,
saturation flows, signal settings, etc and to analyse one node in isolation.