South West Trains, the UK's commuter rail franchise, is investing GBP2.2m in a regenerative braking project to save energy and make its trains greener. More than 200 trains on the South West Trains network, which covers south-west England running out of London Waterloo, will be fitted with the new technology.

Energy produced by a standard train braking is currently lost, but the regenerative braking system returns electricity to the third rail system, allowing trains in close proximity to draw on the electrical supply, South West Trains said.

According to South West Trains, the initiative when fully implemented is conservatively expected to save 15 million kWh of electricity annually, enough to power more than 3,500 UK homes for an entire year. The project when completed is expected to reduce annual fleet CO2e emissions at South West Trains by around 8,000 tonnes, based on 5% of the energy from braking being picked up by another train.

The first two trains, part of the Class 458 fleet, are now starting to test the technology in passenger service on the London Waterloo-Guildford and London Waterloo-Reading routes.

The whole fleet of 30 Class 458 trains is expected to be fitted with the new regenerative braking software by the end of May 2010. The system will then be rolled out to South West Trains’ fleet of 172 Desiro trains.

Christian Roth, engineering director of South West Trains, said: “The roll-out of the regenerative braking system will deliver a significant step-forward in the environmental performance of our trains. Trains are already one of the most environmentally-friendly forms of transport and this new investment will provide our passengers with an even greener and smarter way to travel.

“We estimate that our energy consumption on the Suburban network, where the first trials are taking place, will be reduced by up to 8%. As well as the obvious cost-saving benefits, we are also ensuring that energy previously lost is being put to good use by recycling it and helping to power other trains.”

The regenerative braking project, which is being carried out in partnership with Network Rail and rolling stock providers Alstom and Siemens, is part of a GBP11m investment across Stagecoach Group as part of its new sustainability strategy.

Stagecoach Group is aiming to reduce further the carbon emissions from its bus and rail operations in the UK and North America as part of a five-year program, from 2009-10 to 2013-14. The group is targeting an overall reduction of 8% in buildings CO2e emissions and a cut of 3% in annual fleet transport CO2e emissions.