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Modelling UK rail demand and capacity to 2100

Dr Simon Blainey and Professor John Preston of the Transportation Research Group at the University of Southampton describe an ambitious forecasting project for rail demand.


nyone who has had any involvement in rail demand forecasting will know that it is far from easy to correctly predict patterns of rail use over the next fi ve years, so why would you even try to predict these same patterns up to the end of the century?

Well, that’s exactly what the Infrastructure Transitions Research Consortium (ITRC) is trying to do, and this article will explain why.

We live in a world where fossil fuels and energy are likely to become increasingly expensive, and where there is an urgent need to reduce carbon emissions. In such a future rail’s importance as a transport mode will only grow. This means that signifi cant investment will be required in rail infrastructure, but as rail assets have extremely long lifespans and as there are only limited funds available for infrastructure expansion it is very important that this infrastructure is built in places where it will provide lasting benefi ts.

Modelling the future

The aim of the ITRC modelling is therefore to support infrastructure decision making by providing an indication of where the demand for rail and pressure on infrastructure are likely to be greatest in the future.

ITRC is a consortium of seven universities with industry and government partners, working across the energy, transport, waste and water sectors to develop a new generation of simulation models and tools. The authors are based at the University of Southampton’s Transportation Research Group, and have led the development of the transport model, which predicts demand and capacity utilisation for road, air and sea transport as well as for rail.

While there are a lot of existing rail forecasting models, none of them met the requirements for the ITRC research. These were that the model would produce forecasts at the local authority level for the period 2011-2100, with a run time

of less than fi ve minutes (we need to run the model several hundred times), using open source data and with the capability to represent electrifi cation and capacity enhancements. The model forecasts total passenger trip ends within 144 local authority zones, and the total number of trains on 237 links connecting these zones. Forecasts are based on predicted changes in demand drivers including population, GVA (Gross Value Added – a measure of economic activity), journey times, the cost of rail travel and of motoring, and delays, with feedback between delays and capacity utilisation.

The model has been developed into an easy-to- use Windows-based software tool, and is now being used to model a range of future strategies and scenarios. Scenarios represent changes in external factors, with a range of possible futures generated elsewhere in ITRC, while strategies represent the future characteristics of the rail industry, including the construction of new infrastructure, and changes in the extent and rate of electrifi cation, maximum line capacity (for example through ERTMS), fuel effi ciency, journey times, and pricing.

Up and up

So what do the results show? Well, modelling work is still on-going, but initial results suggest that under virtually all the scenarios and strategies tested rail travel is likely to continue to grow signifi cantly over the remainder of the 21st century, as illustrated by Figure 1 which

Below: Total interzonal trains 2010-2100 under three future external scenarios.

shows the predicted total number of interzonal trains with a strategy that involves rapid electrifi cation (i.e. a continuation of current policies) and fuel effi ciency improvements under three possible future external scenarios.

Figure 1 appears to indicate an extremely healthy future for Britain’s railways, but are these forecasts really realistic, and can such growth in traffi c be accommodated on the network? Sensitivity testing of the models is currently underway to establish whether, for example, maximum capacity values have been set too high, but accommodating even a relatively small proportion of this growth will pose a signifi cant challenge for the rail industry. If the high growth assumptions are realised in reality, then capacity on many parts of the network will be full well before 2100. Some scenarios would therefore require extremely large scale infrastructure expansion to keep pace with demand, and this may not be affordable in practice.

Nevertheless, the advantage of modelling a wide range of futures is that it demonstrates the possible demands that the industry may need to deal with, and this information can inform the industry’s long-term planning. The ITRC model should provide an indication of where on the network demand growth and pressure on capacity are likely to be greatest, allowing infrastructure investment to be targeted where it is needed most. Ultimately, the modelling work highlights the need for the rail industry to engage in long term planning to enable it to meet the challenges of the 21st century.

Dr Simon Blainey


rail technology magazine Aug/Sep 13 | 17

Prof John Preston

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