OK, let's try the maths - 200 people in 200 SUV's create less of a carbon footprint than 200 people in a train.

Never-told stories of this nature include the fact that a Toyota Prius, by virtue of its manufacturing demands, has a carbon footprint approximately equivalent in its lifetime to that of 10 Dodge Viper V10s combined... Another thing is that cows farmed for beef alone emit more harmful gases than all the cars on earth combined... MOO-hahahaha!

The result of this research misses the point, entirely. Of course it's greener to travel four in an SUV, if the alternative is a train 1/4 full. But that is simply not the reality. Car-pooling at that efficiency is an extremely rare scenario in any developed nation. However, if we consider a real-world example, where public transport is used to near-maximum capacity at peak hour, then it FAR out-greens the realistic picture of a single person per vehicle. The study also misses another crucial point. Trains rely on a country's electricity grid. Any vehicle running on a standard combustion engine do not. Although power grids are supplied primarily by C02-emitting coal furnaces, they have the ability to change that source. Governments should be thinking long-term, to decommission all coal power stations and replace them with green sources such as wind & wave farms, solar-thermal plants and even suburban (i.e. private) generated excess energy that is fed back into the grid. This reduces the carbon footprint of any electric transport, for instance trains and electric vehicles. It DOES NOT make green the internal combustion engine of today's motorised transport, and as such will never make Camrys, Trailblazers, Ford F-150s and the like (used by these researchers) a long-term way to a greener planet.

Either this is lousy reporting or the paper is flawed. Comparing the total environmental cost of a trip made by train as compared to the same trip made by a car is a false comparison. The correct comparison should be the marginal environmental cost. In other words, if a commuter gets on a scheduled train to travel into town, the marginal eco-cost is zero because the train is already making the journey. If the same commuter fires up their piously green car, the marginal eco-cost is not zero because now the car is going to use fuel, oil, tyres and so on which it would not have used had it been left in the garage.

Finally, finally, scientists see the light! (so to speak). The real measure of a transport medium's "greenness" is the average amount of greenhouse gases produced for each kilogram moved over the lifetime of that medium. And the production of carbon dioxide for that kilogram moved includes production (hey, think even of the workers commuting to the factories), construction (ditto), maintenance (ditto), direct fuel consumed for movement, etc. But this is moving in the right direction, finally. Let's hope governments, decision-makers and the population at large will soon see the light too.