Arup for Sheffield City Council
Build a large model incorporating route choice to model the effects of public transport priority proposals and help develop new transport models.
The Sheffield City Centre Aimsun Model has been developed by Arup for Sheffield City Council over a number of years. It was originally intended to test the impact of a major development proposal and has subsequently been expanded and developed to cover the inner ring road and many of the surrounding streets.
The latest version of Arup’s model uses the integrated mesoscopic and microscopic models within the Aimsun software to tackle the route choice problem within the complex city centre environment.
Arup used the mesoscopic model to determine a dynamic user equilibrium (representing habitual route choice), which was then used within the microsimulation model together with dynamically chosen paths (representing drivers reacting to congestion), to realistically represent route choice on the network.
The Sheffield model includes buses, the Sheffield Supertram infrastructure, bus rapid transit (BRT) vehicles, including both segregated running and sections where the vehicles run on-street in general traffic, which have a considerable impact on the operation of the network. These larger models incorporating route choice allow the effects of public transport priority proposals to be modelled over a much wider area, allowing, for example, the assessment of the impact of the redistribution of traffic due to reduced capacity.
Due to the way in which microsimulation models treat traffic signals, they are able to model bus priority at bus pre-signals and also pre-emption at traffic signal controlled junctions.
In summary, microsimulation provides an effective way to inform the design and model the effects of public transport priority measures. Over time these large models gradually gain in legacy value and can be re-used for many different purposes.
A number of companies and research institutes are developing advanced adaptive control algorithms. The integration of SPEKTR and Aimsun allows project developers to test the effectiveness of current algorithms and compare them with more innovative algorithmic pilots. This integration exemplifies what Aimsun is all about: openness and possibility.