The Air Quality Cluster Group of the West London Alliance (WLA) has commissioned TRL to develop a combined transport and emissions model which is tailored for West London. The model will be required to provide detailed information on traffic movements across the whole of the West London area, to allow the assessment of air quality issues at locations other than the Heathrow area. The model will also need to address the uncertainties of combining transport modelling at different spatial scales. The transport modelling requirements and capabilities will need to be defined in terms of emissions and air quality parameters, rather than in terms of infrastructure or traffic management. Finally, the model will need to have a scenario modelling capability.

This report defines the broad specification of such a traffic model, its data requirements, and how it will interact with other elements of the modelling framework. The report concludes that a SATURN traffic model could be constructed, covering at least the WLA members’ Boroughs. Costs and timings involved in the construction and validation of such a traffic model are presented, with an assumed start in April 2007, being dependant on ongoing work in other regional models.

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