Research carried out by boffins in California appears to have seriously undermined a major piece of received wisdom regarding transport: namely, the belief that railways are more eco-friendly than airliners.
The cage-rattling analysis comes from profs at the Department of Civil and Environmental Engineering at UC Berkeley. Rather than merely considering the carbon emissions resulting from fuel burned, the researchers considered every ecological impact created by having a given means of transport. Carbon or other greenhouse-gas emissions resulting from manufacture of concrete and steel, generation of electricity, manufacture of rolling stock etc. were all accounted for with respect to railways: and in the case of aircraft, building of airports and other associated infrastructure was included along with manufacture of the planes and so on.
According to the Berkeley boffins, the added greenhouse burden of construction, manufacturing, supply chain etc. etc. adds 155 per cent to the impact of railways, compared to "tailpipe emissions" arising in use. For road vehicles the increase is 63 per cent. But for aircraft it's just 31 per cent - the low figure being partly because aircraft emit a lot of exhaust in service, and partly because they need relatively little infrastructure, materials and so on.
What this adds up to, according to the engineers, is that the highly energy-efficient light-rail system in Boston - where a lot of electricity is fossil generated - has the same environmental impact when half full as a medium-sized airliner with 38 per cent occupancy. The virtuous public transport system is actually more environmentally damaging per passenger mile than the fuel-guzzling jet, even at somewhat higher occupancy.
We here on the Reg flying-car desk are particularly bucked by this news, obviously, as it would seem to lend support to our hypothesis that flying cars could be greener than normal ones. Or anyway, greener than trains running half empty.
The Californian engineers' paper is published online (free) today, in the journal Environmental Research Letters. ®