Trials have begun which could lead to a fleet of battery-powered trains running on Britain's railways.
Network Rail (NR) has fitted batteries to a class 379 train, which normally operates using electricity drawn from overhead power lines.
The project could enable train operators to bridge gaps in electrification and cover areas where building overhead power lines would be too expensive and complicated.
"Over the next five years, NR has a target to reduce the cost of running Britain's railway by a further 20 per cent,” said NR senior engineer James Ambrose.
"At the same time, we are always looking for ways to make the railway greener too. This project has the potential to contribute significantly towards both those goals."
Normally in use with the Abellio Greater Anglia train company, the modified train is now being tested at trainmaker Bombardier's facility at Derby.
The plan is for the Derby trials to lead to a series of high-speed tests at the Rail Innovation and Development Centre (RIDC) in Nottinghamshire later this year.