Appendix D Model audit checklist

General information

Check if a model specification and detail is available for:

  • The type of model used
  • Geographic area covered by the model and the level of zonal disaggregation
  • Tabulation of land use assumptions for all modelled years
  • The transport networks (active, public transport ,highway, freight) included and their details
  • The time periods modelled
  • The vehicle types modelled
  • How the external trips are modelled.

Data sources

Check if a data source description and the source’s reliability are available for:

  • Transport network data (link lengths, link types, free flow speeds, capacities, number of lanes)
  • Travel data and collection methods (traffic counts, origin–destination surveys)
  • Source and coverage of travel data and collection methods (household travel surveys, origin-destination surveys, stated preference surveys)
  • Other.


Check for details on:

  • The description of each step in the development of the Reference (Base) Year and forecast trip matrices, including methods, assumptions, parameters and factors applied – include details of any matrix estimation procedures that have been used
  • Evidence of matrix fit to observed data (screenlines, comparison with independent origin–destination flows)
  • Evidence of sensitivity testing of input parameters or elasticities
  • Detail on the matrix methods or techniques used – if variable matrix methods or growth constraint techniques have been used, provide details on the method and parameters adopted and the justification for the approach
  • Description of the trip generation, trip distribution and mode choice modules by trip purpose, including a listing of all variables.
  • Description of special trip generators (airports, ports).
  • The basis for the development of a commercial vehicle matrix.


Check for details on the:

  • Description of how the transport network was developed
  • Assignment method used (incremental, equilibrium, volume-averaging, other)
  • Generalised cost formulations used for route choice to include the methodology for incorporating tolls on route choice
  • Volume delay functions adopted (equations, coefficients, calibration, validation)
  • Any intersection modelling being undertaken and the basis it is being undertaken on.
  • Outcomes of the model validation tests for each step of the 4-step modelling system.


Check for details on:

  • Comparison of forecast year growth rates with historical trends (land use, household size, car ownership, traffic volumes, commercial vehicle volumes)
  • Average growth across screenlines to ensure local growth is reasonable
  • Comparisons with other forecasts (if any).