ITRC transport modelling for the OxCam Arc

Along with colleagues, Dr Simon Blainey has been researching and analysing transport infrastructure to support the wider analysis from ITRC (UK Infrastructure Transitions Research Consortium). This research has been put together for interested parties to consider the ramifications of various planning options for the Oxford-Milton Keynes-Cambridge Arc (Arc).

The transport model consists of three main aspects: railways, airports and roads. For the Arc analysis, the research focused on the impacts of a small number of interventions on traffic on the major road network, and so the resulting evaluation is just an example of the type of work possible in this area.

More detailed analysis in the future could help planners assess policy interventions and future settlement patterns. Variables which could be included are the construction of new infrastructure, the modification of existing infrastructure, technological and behavioural changes and pricing constraints such as the introduction of a congestion charge.

What’s unique about the ITRC’s analysis is the connectivity between the different models and sectors. The researchers in this project have been examining other aspects of the developments planned for the Arc, such as, population location, energy supply and demand, and natural capital. Moving forwards, there is a real opportunity to hone the models and the scenarios produced so they can be used by the Arc planners. The model can be used as a basis to analyse the impact of the interdependencies between these areas before finalising plans and budgets.

The main road transport scenario we have been analysing is the Expressway, a combination of new construction and road expansion on the corridor between Oxford to Cambridge. Some of the initial results from our modelling indicate that if the new Expressway is built, its impact on journey times is likely to be highly spatially variable. This means that whilst it would likely provide the fastest route between Oxford and Cambridge, the wider benefits will be very much dependent on exactly where people are trying to get to and from.

The results

The analysis indicates that whilst you would expect the population developments anticipated in the Arc to lead to growth in East-West traffic, the Expressway could actually lead to increases in North-South journey times. The increase in journey time is applicable for trips not directly connected to the Arc but which cross the Expressway route – for example, people driving from the north of England to London.

In addition, given the scale of anticipated population growth in the area, the level of additional road capacity included in the model is quite limited. This could suggest that instead of additional roads, investment in alternative transport modes or other options to reduce road traffic (such as car sharing or congestion charges) need to be explored. Although it is hard to make definite predictions at this stage, our findings certainly indicate that we need to be smarter in the way we think about settlements and land-use patterns, and that planning should look at ways to minimise growth in traffic.

Moreover, the road connectivity and transport connectively within planned new settlements is just as important as the connectivity between them. Going forwards, the Arc is a golden opportunity to make sure we get it right in terms of providing transport solutions within new population developments.  This will though of course impact on infrastructure costs as some new or expanded settlements could be substantial towns, or cities, where significant investment may be required.

Some of the headline findings:

  • The high-population-growth scenarios being suggested are likely to lead to a substantial increase in vehicle kilometres driven within local authorities and could result in substantial congestion levels.
  • If the high level of electric vehicles predicted in our analysis comes to fruition, it could result in an 80% drop in direct carbon emissions compared to the existing level of outputs from vehicle traffic.
  • A reduction in road carbon emissions does need to be viewed in an overall context, however. If high market share for electric vehicles substantially increases the overall electricity demand, analysis needs to look at how that energy is generated as a whole, to determine the extent to which total carbon emission savings are realised.


Our transport analysis should very much be viewed as giving a big picture overview. It is intended to help make people aware of the range of issues involved in a development of the scale and complexity of the Arc, and further analysis at various stages will be necessary in order to help local authorities, governments and other stakeholders to achieve the big ambitions of the Arc.


Find out more about Simon’s work in the Executive Summary of the ITRC-MISTRAL report on the analysis of the OxCam Arc or request the full report here.


Simon Blainey

Associate Professor in Transportation, University of Southampton Read more