The rail industry's CO2 emissions have dropped by about a quarter since 1996 and the sector is now responsible for about 0.5% of the UK's total carbon emissions.
Figures from the Association of Train Operating Companies (ATOC) suggest that rail's carbon emissions are now a quarter of those from the aviation industry and half of those from road travel.
The industry is now looking at ways to improve this through better driving techniques, more efficient trains and reducing emissions from stations and buildings, delegates heard at the Reducing Rail's Carbon Footprint conference, in London.
Many sectors of the industry are also campaigning for more widespread electrification of the rail network.
Only 39% of Britain's network is currently electrified, but could save up to 40% of the carbon emissions used by diesel trains.
Richard Davies, director of strategic policy at ATOC, said: "One of the key things we are keen on is electrification, mainly from a cost-saving point of view, but also from a carbon-saving point of view.
"Clearly there are big savings in energy terms from electrification - maybe half a million tonnes of CO2."
Former rail engineer and industry journalist Roger Ford told delegates: "The reason why we should electrify is not to save the planet - it's because an electric railway is a better railway by whatever definition of better you care to apply."
He said that Government should adopt a rolling programme to electrify the railway, starting with the most heavily used and obvious routes before filling in gaps.
"We can all see gaps in the electric network that, if closed, would allow a lot of diesel trains not to run," he said.
He added: "The mood in the industry has switched from dogged defiance to 'let's go'."
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