By Richard Black
Environment correspondent, BBC News website
The UK needs a "modal shift" from road to rail if greenhouse gas emissions from transport are to be curbed, a report concludes.
The report urges pricing of transport impacts such as air quality
The Institution of Mechanical Engineers (IMechE) says changes are needed to government policies on transport pricing, energy and town planning.
A train journey can produce about one tenth of the carbon emissions generated if the same trip is made by air.
The report's authors say substantial investment in the railways is needed.
"We have ambitious government targets for transport emissions, but transport emissions are static," said Cliff Perry, vice president of IMechE's Railway Division and a former head of Thameslink under British Rail.
"Eighty-five percent of transport emissions come from roads, so if we are serious about doing something, we must hit road transport."
Comparing emissions between various forms of transport is not a straightforward matter, as factors such as the efficiency of engines, the number of people on board and, for electric trains, how the electricity was generated all affect the final equation.
IMechE calculates that on average London to Paris trips, people travelling by car generate two and a half times more CO2 than those relaxing in a train, while an air passenger produces 10 times more.
But achieving a substantial shift from road to rail would need a coherent policy covering issues such as how secure passengers feel, the convenience of connections, the cost of tickets, and reliability.
Road pricing is set to spread to more areas of the UK
Emissions from electric trains are of course much lower if the electricity comes mainly from low-carbon sources.
The report's authors said Britain could learn much from countries with superb rail systems, such as Japan, where trains routinely arrive and depart on the minute, equipment failures are rare, and where many railway stations form centrepieces of cities and districts.
"Spatial planning has to be considered, and new developments should take account of what we can learn from the Japanese system," observed Bill Banks from Strathclyde University, deputy president of IMechE.
Train companies should consider offering services like wi-fi internet access throughout, and improving catering services so that rail travel becomes something to look forward to.
The report's authors acknowledge that the price of rail tickets can be prohibitive, sometimes costing many times more than the air equivalent.
One remedy they suggest is proper pricing of all transport options to include environmental impacts.
They also suggest tickets could include references to the relative carbon output of different modes of transport.
Whatever changes are made, IMechE considers the "modal shift" will necessitate some investment in infrastructure, including new high-speed lines that can carry more trains significantly faster than the UK's existing stock.