If current trends continue, a time will come in the next decade when the carbon imprint of travelling by high-speed diesel train will be heavier than that of sharing a family car. This is not how the future of transport was supposed to look. It belies a major plank of received wisdom on the environmental impact of trains and cars – namely that rail is always and inevitably “greener”. Even so, it should not trigger a new rush of passengers from carriages to cars.

Road users and the automotive industry are routinely cast as villains in the environmental debate. This is simplistic. In rural areas denuded of public transport, cars are the only alternative to isolation. In emissions tests, new cars are showing greater efficiency gains than most other forms of transport. But the most startling finding in a new study of transport energy use – the worsening efficiency of diesel trains relative to cars – is not an argument for urging passengers to abandon the railways for the sake of the planet. It is, instead, an argument for the long overdue electrification of Britain’s network.

The Lancaster University report on “traction energy metrics” ranks this country’s locomotives in ways that will fascinate trainspotters, but should interest everyone else as well. Every electric engine now in use, except one model, is substantially more efficient than even the cleanest diesel. The exception is the Eurostar, on account of its high speed, but even this emerges as more efficient than all diesels when the power generation industry’s steady move away from coal in favour of cleaner-burning gas is taken into account. And the most widely used electric locomotives are fully two and a half times more efficient in terms of carbon dioxide emitted per passenger-mile than are powered cars.

For planners and policymakers concerned chiefly with curbing carbon emissions, therefore, the long-term goal is clear. The debate on climate change science continues. Climate change evangelists should not pretend that it is over by presenting new research on solar activity as conclusive when it is not, or by ignoring such factors as the increasing proportion of weather stations in urban and therefore hotter-than-average locations. But the planet deserves the benefit of the doubt, and electric trains deserve their status of official inter-city transport mode of choice.

Electrification – in the Soviet Union – was seen as so epic an undertaking that only opera could reflect its scale. In Britain, rail electrification since the 1950s has been fraught with cost overruns and operational glitches. This need not be the case in the 21st century. Most major arterial routes are already electrified. Many of those on which diesel trains still run need work on only short sections of track to become fully electrified. And while few significant efficiency gains are expected from diesel technology in the future, electric trains are already more efficient in absolute terms and offer the prospect of progressively lower carbon output as the national grid switches from coal-dependency to a new mix of gas, nuclear and renewable sources.

Greater efficiency means lower long-term energy costs. The most successful solutions to global warming will come from the creativity of the market, but, with infrastructure, the Government must take a lead. Electrify the railways as soon as possible.