Research ready to use
More efficient and safer power changeover Making the most of traction power supply
Differential speeds for freight trains to shorten journey times
A new version of the Wheel Tread Damage Guide is now available
Bringing together the knowledge required to plan new power changeover sites and choose appropriate systems.
It is now common for trains to switch traction power—such as from overhead line to third rail, diesel to electric, or battery to diesel.
Power changeover (PCO) arrangements have been used since the 1970s but are now widespread and complex. Many passenger and freight operators routinely use these systems.
Modern multi-mode rolling stock has different methods of PCO. When new multi-mode freight locomotives join the network, with services crossing different routes, drivers could experience a patchwork of PCO systems.
Our research aimed to improve the reliability of the next generation of multi-mode trains and mitigate challenges caused by the growing complexity and extension of PCO sites.
We assessed the safety, performance, and operational impacts of PCO systems. This analysis was based on both the failure modes listed in relevant standards and 53 incidents where damage occurred to the train or infrastructure between 2014 and 2024.
We also identified and assessed mitigations. These ranged from developing specific local instructions to providing audible warnings to drivers.
Our findings support a systems approach that integrates human factors, operability, and maintainability throughout the process of designing new PCO systems.
This approach also applies to the ongoing use of existing PCO systems by both passenger and freight train operators.
Download the project findings from RSSB's research catalogue (search for T1356).
To discuss the findings, contact Paul Gray, Professional Lead, Engineering.
Short, medium, and longer-term opportunities to better exploit electrified routes.
The technical details and limits for how electric trains use power on the mainline 25 kV AC network have changed over time. Modern traction technologies, including digital power regulation, have been introduced to optimise how trains interact with the power supply and improve efficiency.
However, due to legacy rolling stock and electrical infrastructure, a mix of legacy and contemporary traction power limits are still in use around the network. The origin and justification of these limits is often unclear.
This project, which was delivered as part of the ROSCO-RSSB funding partnership, explored how changing these power settings could make better use of the available electrification capacity. For example, it could allow more trains to run at the same time without power shortages.
We found that:
minimum voltage requirements sometimes create unintended issues. Changes to minimum voltages could unlock extra capacity in the short term.
moving to harmonised automatic current limitation would free up more voltage. This would also ensure fairer power sharing between trains.
standards already allow lower voltage thresholds for regenerative braking. Clarifying requirements would further improve efficiency.
outdated harmonic current limits should be removed. Defining a modern harmonic profile will help with grid planning and energy subsystem design.
allowing rolling stock to exceed the nominal 300 A current limit offers little real-world benefit. As older fleets retire, modern rolling stock can match or beat the performance of older trains, even within the 300 A threshold. This could boost system voltage capacity.
‘This work is truly excellent and lays the foundation for significant change in how traction power capacity is assessed in the future.’
Richard Stainton, Engineering Expert (Electrification), Network Rail Technical Authority
Download the project findings from RSSB's research catalogue (search for T1331).
To discuss the project, contact Mark Hanham, Senior Research Analyst.
Research challenged outdated assumptions that restricted the speed of some rolling stock.
Speed limits for freight trains depend partly on their assumed braking capabilities. On any stretch of line, speeds are set by considering the space between signals and the train’s ability to stop in time. The braking assumptions are conservative to account for trains with poor braking.
Our previous analysis found that many wagons have braking performance that far exceeds the assumptions in current standards. This suggests that permissible speeds for some freight services are much lower than they need to be. A potential solution is the implementation of differential speed limits, which would allow rolling stock with better braking performance to travel at higher speeds on a given stretch of line.
This project identified criteria that a freight train must satisfy to travel safely at higher speeds. It also identified network locations where freight speed differentials could be implemented. These opportunities are concentrated in the southern region, associated with an historical arrangement for longer signalling distances that used the ‘2/3rd rule’ (freight trains operating at two-thirds of the line’s design speed).
Allowing some freight to travel faster will deliver reliability gains for those routes. It will also support the freight growth target, without large investment and without compromising safety.
'It is welcome news that the research has shown there is an opportunity to increase the speed of some freight trains.'
Paul Ashton, Head of Safety, Network Rail
Keep up to date with the project at RSSB's research catalogue (search for T1348).
We are now working with Network Rail’s Southern Region to explore the opportunities identified through this research. We welcome discussions from other parts of the network and industry to identify and develop additional opportunities, including partnerships with freight operators. For further information, please contact Aaron Rostron-Barrett, Head of Research Delivery.
Incorporating the latest research, the updated resource will help train operators and maintainers optimise wheelset management.
The original Wheel Tread Damage Guide published 12 years ago has been a valuable source of information for industry. With fleets changing and the science that underpins the guide evolving, it was time to review and update the guidance.
The new guide provides vital information for vehicle operators, maintainers, and owners on:
identifying and categorising wheel tread damage
the role of condition monitoring in improving detection and early intervention
mitigations for different damage mechanisms
implications for wheelset maintenance policies and practices.
The updated guide, delivered through the RSSB and University of Huddersfield partnership, is informed by the latest research. These findings were presented at a series of workshops, enabling frontline staff to thoroughly explore the updated good practice. Staff also had opportunities to discuss solutions and strategies to optimise wheelset life.
Depot workshops were hosted by Transport for Wales at Cardiff Canton and Siemens at Manchester Ardwick. A final event was held at our London office in October.
We are grateful for delegates’ engagement on key trends, challenges, and opportunities for the future. Their feedback is invaluable and has informed the finalised guide.
'This update to the Wheel Tread Damage Management Guide is a valuable source of best practice that can help maximise wheelset life and ultimately save money. It makes a compelling case for the value of adopting more mature monitoring and analysis techniques, which can generate considerable savings on wheelsets and turning costs.'
Simon Jarrett, Interim Head of Fleet Engineering, Chiltern Railway
Watch a video and download the new Wheel Tread Damage Guide at RSSB's research catalogue (search for COF-UOH-82).
Contact Melissa Frewin, Senior Partnership and Research Grant Manager, with any questions.
