Next stop, the future
Southampton research is providing evidence-based solutions for improving rail networks.
The UK’s rail networks are based largely on a Victorian infrastructure, dating back to the mid 19th century. These aged tracks come with a hefty maintenance bill: Network Rail spends around half of its £9bn budget on repairs and renewal each year. Research at Southampton is set to reduce these costs and enable greener and more efficient rail travel.
Across the UK, most of our railway track is built on ballast – a bed of stones to reduce the stresses transmitted from the moving train to the ground below. This poses a fundamental problem: the ballast tends to move over time due to the vibrations from the trains travelling along the track.
“The situation with the railways in the UK is a bit like energy efficiency in housing: the big challenge is retrofitting current homes to be energy efficient, and ballasted track is the retrofit of the transport infrastructure,” explains William Powrie, Professor of Geotechnical Engineering.
Extending the interval between track repairs and maintenance by a factor of two or three would be a game-changer, and this is what the Southampton team aims to achieve, says William. As part of the prestigious £3.1m ‘Track 21’ project, funded by the Engineering and Physical Sciences Research Council (EPSRC), William and his team have developed and assessed techniques that rail companies could use to mitigate these problems. “For example, we looked at changing the grading of the ballast to improve mechanical interlocking of the stones, and retaining vegetation to provide deep-rooted suctions that help prevent embankments from failing,” explains William. These projects were ranked as world-class in the most recent Research Excellence Framework (REF 2014).
Five things you may not know about rail:
- Passenger rail journeys in Great Britain reached 1.69billion in 2015/2016
- There were 28 complaints made per 100,000 train journeys in 2015/2016, with punctuality / reliability the most common cause for complaint
- There was 15,760km of rail route in Great Britain in 2014/2015
- The UK was ranked 16th out of 104 countries for quality of railroad infrastructure in 2014/2015
- 17.8 billion net tonne kilometres of freight was moved by rail in 2015 / 2016
Improving track for the future
Southampton researchers are leading a consortium of UK institutions (the universities of Huddersfield, Birmingham and Nottingham) in a new £8.5m research programme, ‘Track to the Future’. The aim is to develop railway track that will cost less and last longer, with reduced maintenance needs and improved environmental performance.
“We are testing several aspects that could improve performance, including putting rubber pads under railway sleepers to spread the contact and prevent the ballast from moving so much, and using strips of polypropylene in the ballast to help lock it in place,” says William.
These ideas are tested rigorously in the lab and the field. “We have a rig on which we can test a single sleeper bay and subject it to three million load cycles over a period of 12 days, which is the equivalent of two to three years of traffic on a busy railway line,” William explains. The team also carries out extensive field monitoring – for example using sensors that respond to the velocity of vibration of the track, and embedding devices into ballast particles to measure the accelerations to which they are subjected.
Points, crossings and transitions onto bridges take up a large proportion of any railway company’s maintenance budget, despite making up only a small percentage of the total length of track. William and his team are working with Huddersfield University to improve the design of the metalwork at the junction, including the potential use of techniques such as 3D printing, to achieve a smoother transition of the train through the crossing, thereby reducing wear and tear. Work based in the University’s Institute of Sound and Vibration Research (ISVR) is looking at ways to reduce noise – a growing concern for people who live near railway lines.
“The size of the prize of reducing maintenance is substantial, in terms of increased availability, as well as reduced cost,” says William. “The railway is now so busy that the time that can be given to maintenance is very short, and this is only going to get worse: London Underground, which is already very heavily trafficked, will soon be running overnight on Friday and Saturday nights. So low-maintenance track will significantly reduce disruption.”
The situation with the railways in the UK is a bit like energy efficiency in housing: the big challenge is retrofitting current homes to be energy efficient, and ballasted track is the retrofit of the transport infrastructure.
Railway tracks are complex systems: changing one factor can have unintended consequences. “All of our research is building the knowledge base of how the modern rail system really works: over the last few decades our railways have gone from limestone to granite ballast; timber to concrete sleepers; they have changed the shape and type of steel in the rail, and the suspension and wheel profile of the trains. All of these have a significant impact on the system that we need to understand,” William explains.
The Southampton team is working with all the major UK rail operators – Network Rail, London Underground, HS1 and HS2 – as well as European rail operators such as Pro Rail in the Netherlands, to address issues that arise as the nature of railways changes.
“With HS2, for example, we are addressing a concern that under certain conditions high-speed trains on ballasted track may cause particles of ballast to become airborne as a result of aerodynamic forces coupled with ground-borne vibration,” says William. “Our results so far suggest that this problem can be avoided through good design and careful tidying up after maintenance operations”.
Stormier weather resulting from climate change is bringing further challenges for our railways. Through a strategic partnership with Network Rail, Southampton researchers are working to address these. For example, the West Coast Mainline in Scotland has been closed recently because of damage to the foundations of a viaduct over a river caused by the riverbed being washed away. “We are developing novel ways of detecting these types of occurrences as they take place and creating better models of predicting when this type of damaging erosion could happen,” says William.
Current electrification projects are facing multi-billion pound over-runs in cost, mainly because of the inefficient design of support masts for overhead line equipment and their foundations. Our researchers are working with Network Rail to develop more economical design methods to help bring costs back under control.
The size of the prize of reducing maintenance is substantial, in terms of increased availability, as well as reduced cost.
The uniqueness of Southampton’s contribution to affordable, sustainable railway infrastructure engineering is multi-faceted. “First, at the heart of this is our ethos of developing and applying scientific principles to the solution of real-world problems. Applying sound science to solve practical problems is the hallmark of everything we do in teaching, research and enterprise,” William explains. In recent years, William and his team have developed easily deployable techniques for measuring and understanding how the railways are behaving, which together with the outputs from laboratory tests have helped companies to develop more cost-effective maintenance strategies.
“Second, the combination of skills we have here, in terms of civil engineering, fluid dynamics, soil mechanics, structural engineering, sound and vibration, materials and economic modelling, makes Southampton really stand out in this field,” adds William. This gives the research teams the ability to look at all the problems associated with everything from a mixed-traffic railway with historical infrastructure, to a single-purpose new build line. They can take into account externalities from human and socio-economic factors through to the stresses associated with climate change.
“Third, the sheer scale of activity and external funding gives us huge synergies, with multiple benefits for sponsors and stakeholders,” says William. The University runs a vibrant EPSRC-funded Centre for Doctoral Training in Sustainable Infrastructure Systems and, as part of the UK Collaboratorium for Research into Infrastructure and Cities (UKCRIC), we are about to start building the new £40m National Infrastructure Laboratory, which will complete the development of the Boldrewood Innovation Campus.
“This will enable us to continue to develop innovative solutions to infrastructure challenges, train the experts of the future, and drive forward improvements in affordable, sustainable infrastructure across the UK and beyond.”