University of Southampton
Keywords: Affordable railway electrification, arcing decarbonisation net-zero foundations
Sector: Low carbon transportation of goods and people
Project leads: William Powrie CBE, Professor of Geotechnical Engineering, University of Southampton; David Richards, Professor in Ground Engineering, University of Southampton; Paul Lewin, Professor of Electrical Power Engineering, University of Southampton; Andrew McNaughton, Professorial Fellow, University of Southampton
Project collaborators: Richard Stainton, Engineering Expert (Electrification), Network Rail; Robert Ampomah, Chief Technical Officer, Network Rail; Martin Frobisher OBE, Group Safety and Engineering Director, Network Rail; David Clarke, now Senior Technical Advisor and formerly Technical Director, Railway Industry Association; Corporate collaborators including Siemens Mobility, Andromeda.
Issues addressed by the project
In 2021, the UK government’s Transport Select Committee recommended a 30-year programme of electrification projects as part of its long-term rail decarbonisation strategy. Since the 1960s, the UK has taken a financially frugal approach to railway electrification, resulting in the UK lagging behind most European and Asian countries in terms of the proportion of the network that is electrified.
The Great Western Electrification Programme (GWEP), which started in the early 2010s, was the first major UK electrification scheme since the East Coast Main Line a generation previously. Its projected costs rose from £900M in 2013 to £2·8bn in 2016 (National Audit Office, 2016). As a result, the GWEP was cut back significantly, while other electrification schemes, notably for the Midland Main Line (MML), were paused or cancelled.
There was perceived to be a need to provide large clearance distances between existing structures (such as over-line bridges) and the new electrification equipment, leading to a requirement to raise or replace existing structures. Most railway overbridges carry vital utilities (gas, water and electricity) as well as roads, making bridge reconstruction, or even just raising the bridge, both expensive and disruptive to the environment and the local community.
Also, it was believed that foundation piles for the masts or gantries supporting the overhead lines needed to be much longer than on previous schemes, often over 10m in length compared with a previous maximum of 5m.
Future impact of the project
We worked with industry partners to develop new technologies that avoid or substantially reduce the need for historic bridge reconstruction. The first application of this was Cardiff Intersection Bridge, which carries a complicated network of roads and road junctions across the South Wales (Great Western) Main Line. In 2018, research began in partnership with Network Rail, Siemens and others to look at alternatives to demolishing the bridge.
Results showed that when an electric-current-resistant coating was used in combination with specially developed lineside kit, including surge arresters to prevent voltage spikes, insulated supports for the electrically conductive contact wire, and a contact wire cover, a minimum electrical clearance of just 20mm to the bridge and 70mm to the train roof was enough to prevent arcing of current between the trains and the bridge, even in wet and polluted conditions.
The standard electrical clearance had been previously set at 370mm.This research led to a change in the Rail Group Standards, which will ensure long-term cost savings as electrification is rolled out across the UK rail network.
The initial investigation determined that the perceived need for longer piles was because the designers had abandoned the traditional method of pile foundation depth calculation. Instead they were using a new approach based on trying to calculate and limit wire-height deflections in high winds rather than the traditional method of providing an adequate ‘factor of safety’ against overturning.
There was some justification for this, in that the loads associated with the much heavier GWEP structures were outside the evidence-base of the traditional, empirical calculation method. A three-year research programme comprising quantifying the new loads began, undertaking comparative pile length calculations using traditional and new methods, and carrying out field tests to validate the calculations.
This resulted in Network Rail instructing their designers to revert to the traditional method of design, and a reduction in the depth of piles being specified back to a maximum of about 5m with a substantial reduction in cost. The findings of this work were incorporated into an updated Network Rail standard.
Place-based local and regional benefits
Reducing the need for bridge reconstruction makes it possible to justify individual schemes that might otherwise not go ahead at all, or carry out more schemes (the regional benefit). It also reduces disruption to local communities during works to deliver an enhancement to local and regional rail services (the local benefit).
The Cardiff project cited above avoided the need for a £40M reconstruction with major disruption, at a cost of £1M with no impact on local roads. The benefits will continue for as long as there is electrification. For example, the Wigan to Bolton Rail Line, opening late summer 2025, avoided 11 bridge reconstructions out of 14 making an estimated saving of £25M in a £100M project, while on the current Midland Main Line stage to Wigston the project team is quoting £30M savings from avoiding reconstruction of 11 out of 18 bridges.
National and global benefits
The work on foundations led to savings over three years worth an estimated £600M to the UK economy in materials, programme time and carbon. Without the research it is unlikely that the Great Western and Midland Main Line would have been completed, at a cost to the economy estimated by David Clarke (then Technical Director of RIA and author of the RIA Electrification Cost Challenge report 2019) to be over £5.5bn.
A key statement of international and national benefits is the Transport Select Committee report “Trains fit for the future?” dated March 2021. This report notes that in June 2019, the UK Government set legally binding targets to reduce net emissions of greenhouse gases by 100% relative to 1990 levels by 2050 – commonly referred to as the ‘Net Zero’ target.
The report states “For rail to support the UK in achieving its net-zero legislative target, diesel operation would need to reduce and potentially cease”. It accepts Network Rail’s recommendation in its Traction Decarbonisation Network Strategy (TDNS), that 11,700 Single Track Kilometres (76% of the available track) should be electrified.
Supporting the Net Zero target is a national benefit which in turn contributes to the global benefit of reduced carbon emissions. Delivery of the TDNS would remove all but residual emissions of around 50 million kg CO2 per year from freight trains operating beyond the proposed electrified network. This is around 3% of 2020 total traction emissions.
Level of investment and timescale
The research has been a long term project with Network Rail and started in 2011, centred largely on reducing electrical clearances while maintaining safe working conditions. Since then NR has invested £1M – £2M with the University over a wide range of discrete projects, part of a portfolio with several institutions. Work on electrification foundations and structures continues with research contracts running in one case to March 2027.
Risk vs reward
The reward of this investment is set out above: in cash terms alone it has saved hundreds of millions of pounds or, conversely, has justified investments by improving the benefit cost ratio. What is more, the benefits accumulate every year with every electrification project, with a current horizon of 2050.
Further aspects
University of Southampton plays a leading role in rail research in the UK and beyond, collaborating with other institutions and industry to accelerate advances. It leads the UK Rail Research and Innovation Network (UKRRIN) Infrastructure Centre of Excellence, which hosts collaborative research and development by academic and industry partners.
The focus is on applying rigorous scientific theory, interdisciplinary methods and advanced analysis to solve practical real-world problems, making solutions relevant, reliable, transferable and scalable.
This project has led to new industry design guidelines and standards that have influenced engineering practice globally. For example retaining walls and groundwater control, and railway overhead electrification mast foundations. This has lead to enhanced safety, sustainability, resilience, reliability and cost-efficiency.
The new knowledge created through working directly with industry has delivered huge cost savings and environmental benefits. The purpose and outcome is to enable people and communities to enjoy a quality of life underpinned by clean, affordable sustainable transport and the health benefits of Net Zero.
