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FactCheck: is the train still greenest?

By Channel 4 News

Updated on 31 July 2007

Trains are often slow, unreliable and expensive - but still the greenest way to travel, right? The FactCheck Green series continues.

The background

Despite being often tardy and costly, trains are still known as the greenest way to travel.

Planes, meanwhile, burn massive tanks full of kerosene to get them up into the stratosphere. While they cruise at high altitude, the carbon dioxide they release makes twice the contribution to global warming that it would on the ground.

Cars burn a lot of petrol, but at least they do it at ground level. And trains, though heavy, take large numbers of people.

So conventional wisdom says that travelling by plane is always worst, followed by car and then train. So in many cases, environmental damage is usually proportional to convenience.

But is this really true? Calculating the carbon impact of different travel modes depends on so many different factors that it can sometimes produce surprising results. And in a few cases, planes or cars can be greener than trains.

The analysis

The most sensible way to measure the impact of travel is the amount of carbon dioxide (or equivalent) emitted for every mile a passenger travels.

This gives the best assessment of the impact of each individual journey, but the results this kind of analysis produces depend on how many people are in each car or train - so a full train will have a much lower impact than a half empty one.

Under this analysis, travelling by train is almost always greener than car for a single traveller. But put a family of four people in the car, and the emissions per person fall by 75 per cent - so that trip might look greener by road than by rail.

There's also a considerable variation between different kinds of plane and train. The Virgin Voyager trains, for example, are diesels which are almost three times more polluting than cleanest trains in the UK - GNER's electric trains between London and Edinburgh.

Even different planes show a high degree of variability between different models.

Turboprop planes, for example, travel relatively slowly, and create much lower emissions than faster jet aircraft. So much so, that travelling by turboprop aircraft on some routes could be less damaging than travelling by diesel train.

High speed trains also produce much higher carbon dioxide emissions than normal trains - so plans for trains travelling at over 350kmph could offset part of their environmental benefits.

Roger Kemp, professor of Engineering at Lancaster University, has calculated that French-style TGV trains travelling at 350kmph from London to Edinburgh would create more damage than an Airbus on a similar route.

The verdict

Government might be better off trying to push rail travel for businessmen who would otherwise fly or drive on their own in large cars, than targeting families who would otherwise travel in full cars.

If you're a family of four this doesn't necessarily mean that driving is the greenest option.

You face a choice between getting seats on a train that would be travelling anyway (thus having almost no extra impact) or putting an extra car on the road.

So, as with many of today's green dilemmas, there is no easy, hard-and-fast answer. The basic principle that trains are better than cars, and better in turn than planes, is still a useful rule of thumb. But the least damaging thing of all is just to stay at home.

FactCheck rating: 2

How ratings work

Every time a FactCheck article is published we'll give it a rating from zero to five.

The lower end of the scale indicates that the claim in question largerly checks out, while the upper end of the scale suggests misrepresentation, exaggeration, a massaging of statistics and/or language.

In the unlikely event that we award a 5 out of 5, our factcheckers have concluded that the claim under examination has absolutely no basis in fact.

The sources

Environmental Impact of High Speed Rail, Professor Kemp, Lancaster University
Rail Industry admits that it's often greener for families to travel by car, The Times, 13 July 2007
Improving the efficiency of traction energy use. Rail Safety and Standards Board, June 2007

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