Minimising maintenance for London’s new Elizabeth line

The first phase of his research led to changes in the cant – the height of one rail above another in curved track.

On curves, a carefully-calculated reduction in cant helps to even out the forces across the many axles of a train, reducing the risk of rolling contact fatigue (RCF) in rails, a problem which accounts for a significant proportion of Network Rail’s annual maintenance budget on mainline track.

“The reason this was a major issue is that the typical curve radius on the Elizabeth line route is about 500m, where it might be about 1000 or 1500m on a typical main line,” said Dr Allen.  He added that the Elizabeth line also has a particularly large number of curves and it will be carrying huge amounts of traffic – an average of over 380 trains a day.

In order to maintain this capacity, it is important to minimise disruption caused by unplanned maintenance. Exhaustive simulations and calculations have been carried out which have led to changes in track alignment that will reduce both wear and the potential for RCF in curves.

However, some wear and RCF will still occur, and Dr Allen, with his IRR colleague Dr Philip Shackleton, has continued to work with Transport for London (TfL) in order to develop a maintenance planning tool for the Elizabeth line. This is a sophisticated piece of software that enables operators to simulate a wide variety of scenarios and predict what maintenance actions will be required, in order to identify the optimal maintenance strategy.

The application of the software focusses on the Elizabeth line, running through central London and serving 41 stations.  In readiness for December’s opening of the line, engineers are already using the tool developed by Dr Allen and Dr Shackleton in order to plan their maintenance schedule.

The IRR has also investigated the use of premium rail steels, and the potential benefits in terms of maintenance, at specific locations – principally curves – that are most at risk of track damage though RCF.  In addition, there have been vehicle dynamic studies and an analyses of the sites where flange lubrication will be most required.  This can help decide on factors such as the size of the lubrication tank fitted to vehicles.

Tens of thousands of simulations of journeys on the Elizabeth line were undertaken to develop a large dataset which considered a wide range of plausible operating scenarios.  The dataset, which sits within the software, allows TfL to understand the effect of different operating factors, such as the use of lubrication or premium rail steel, on RCF and wear predictions.

The aim is to optimise asset life, minimise maintenance costs and in turn help ensure safe and reliable operation of the tracks.  And the research conducted by the IRR for the Elizabeth line and other new lines such as HS2 is of wider relevance.

“The growth in railways is at record levels, so capacity is the key challenge now,” said Dr Allen. “The sort of tools that we are developing are a key to this.”