altTransport minister Lord Adonis tells us that the government’s intends to replace domestic and short-haul flights with a new high-speed rail network. There are three good reasons to think that this is a terrible idea.

First is the government’s record with large-scale infrastructure projects. The last major project on the railways was the upgrade to the West Coast Main Line, which was initially planned to be finished by 2005, estimated to cost £2bn, and designed to allow trains to travel up to 140mph. It was eventually completed in 2008, at a cost of at least £9bn, and permitting speeds up to 125mph. The government’s estimates for a single 250mph line linking London to the North stand at £20bn, and a decade’s work. Believe them if you wish.

Second is that the railways are not economically viable. Despite the government bearing a large part of the maintenance and capital costs of the rail network, most operators only survive with massive subsidies: Virgin West Coast franchise received £312m last year. Many airlines, despite brutal levels of taxation, still make a profit. It’s nonsense to spend a fortune replacing a mode of transport that is profitable, that generates wealth, with one that destroys it.

Third is that the government’s environmental arguments are ridiculous. Even if we accept their assertion that the construction of new rail networks will make substantial difference to carbon emissions (which many contest), it’s a horrendously expensive way of doing so. Even if the railways replaced every one of the nine billion kilometers flown by domestic passengers last year, the trains omitted no carbon dioxide whatsoever, and the project came in at the lowest possible cost of £20bn, and assuming that airlines currently use the most polluting planes available (165gCO2/km), the cost would be £13,468 per tonne of yearly CO2 emissions avoided. For comparison, CO2 reduction at coal-fired power stations costs in the region of £20 per tonne.

If it ever gets built, this railway will be little more than a monument to ministerial ego, financial insanity and environmental hysteria.