1.1km of plain line track has been replaced on a stretch of railway line in south London using a suite of low-carbon, sustainable materials.
The railway has successfully delivered the UK’s first low-carbon track renewal, combining green steel rail, low-carbon concrete, recycled ballast and renewable biofueled trains to cut emissions without compromising performance.
Led by the Southern Renewals Enterprise (SRE) – Network Rail’s integrated delivery team in the south of England – the project saw VolkerRail, the SRE’s Track business partner, renew 1,150 yards of plain line track between Honor Oak Park and Forest Hill.
This was carried out using new products developed by Network Rail Supply Chain Operations (SCO).
The track was fully welded, stressed, and handed back early at line speed.
Challenge
Materials account for a significant share of the overall carbon footprint in track renewals, as much as 90 percent.
The key contributors are steel rails, concrete sleepers, and ballast, all traditionally produced through carbon-intensive processes.
Solution
To address this challenge, the project team worked with Network Rail SCO to deliver a 'First in Rail' renewal showcasing multiple low-carbon innovations working together in a live operational environment. These included:
• Green steel rail produced using an electric arc furnace, achieving around 60 percent lower carbon intensity compared with traditional blast furnace steel
• Low-carbon concrete sleepers, designed to deliver an estimated 40 percent reduction in embodied carbon
• Recycled blended ballast, achieving up to 13 percent carbon savings by reducing the need for virgin aggregate
• ISCC-certified renewable biofuel (commonly referred to as HVO)
• Solar-powered welfare units, reducing the need for diesel generators and cutting on-site emissions
This project marks the first time all three primary track components – rail, sleepers, and ballast – have achieved verified carbon reductions on a single renewal in the South of England, while also using HVO-fuelled trains.
Results and impact
The combination of these innovations resulted in 63 percent (581 tCO2e) carbon emissions avoided compared with baseline materials and transport methods – the annual emissions of around 200 UK households.
Across the first year of the programme, April 2024 to April 2025, the SRE achieved a 10.2 percent reduction in whole-life carbon against the baseline, underscoring our progress toward a more sustainable and future-proofed rail network.
Beyond the carbon savings, the project demonstrated the power of collaboration between SRE Track, Network Rail Supply Chain Operations (SCO), the Environment & Sustainability team, and partners across the supply chain.
Building momentum
Green steel and low-carbon sleepers are now in use across SRE projects, and the successful use of blended ballast in the South represents a key milestone in scaling low-carbon materials nationally. Further investment in these supply chains will continue this growth.
As Dave Sutton, SRE Track’s Project Lead, noted: “This project shows what’s possible when innovation and teamwork come together.
“It’s the first of many greener renewals we plan to deliver, helping us move steadily toward Network Rail’s net zero goals.”
“Congratulations to everyone who contributed to delivering this significant achievement,” Liz Baldwin, SID Director, added.
“It is a proud moment for our team and a powerful signal of what’s to come.
“The success of this project demonstrates that sustainable rail delivery is not only possible, it’s scalable.”
Looking ahead
While challenges remain, such as scaling supply chains, ensuring biofuel sustainability, and managing the costs of low-carbon materials, the Honor Oak Park renewal offers a practical example of how the rail industry can embed sustainability into everyday delivery.
It contributes directly to Network Rail’s commitment to align with the UK’s 2050 net zero target, providing a replicable model for future renewals across the country, and striving towards a simpler, better and greener railway.