South East Wales Transport Model: Frequency model results
13 Sep 2018
This report documents the methodology and estimation results of the frequency model components of the South East Wales Transport Model (SEWTM).
Researchers developed models capable of predicting levels of transport demand in South East Wales in response to a range of different policy options and in light of demographic changes.
They based the model on an existing one they had developed for the West Midlands, modifying it as needed based on local data. The resulting model closely predicts share of transport modes, though at times under-predicted car driver share.
In 2018 the Welsh Government commissioned RAND Europe, together with Mott MacDonald and David Simmonds Consultancy, to develop a new transport model for South East Wales. The new model was required for the assessment of a range of transport policy options, including schemes to improve the public transport services across the region.
The aim of RAND Europe’s contribution to the project was to develop new models capable of predicting the levels of transport demand in South East Wales, in response to a range of different policy options and in the light of demographic changes. Separate models were designed in relation to different purposes for travel, as well as the various modes of transport.
The approach that RAND Europe followed in this study was to take the detailed transport models they had developed together with Mott MacDonald for the West Midlands region, and transfer them to a South East Wales context. This transfer approach allowed a detailed, policy responsive model to be developed for South East Wales, both at a lower cost and over a shorter timescale compared to developing a new model from scratch.
Household interview data is important for providing a representative evidence base for model estimation. We recommend a minimum of 4,000 household interviews be collected which include full destination information, to allow the ability to take account of variations in cost sensitivity in South East Wales. Interviewers should also be carefully briefed on the difference between commuter and employer business travel when household interview data is collected.
The approach to estimating frequency models for education purposes needs revisiting if there are any changes to the school leaving age.
We recommend that realism tests are undertaken to verify that the model elasticities are WebTAG compliant.