The problem is one of capacity on the railways, something that could be most easily solved by longer platforms and longer trains, not speed.
Indeed the evidence suggests that the speed INCREASES the economic dominance of London, and rather than increasing the supply of Jobs in the cities it serves, may see even more of the UK’s economic output originate in London.
The economic benefits of shorter journey times are overstated, mainly because people can work on trains.
If HS1 is anything to go by, most people use the slow line, with only those on expenses using the high speed line. This is the market signalling how much value people put on a short journey time – they’ll take it, but only if they’re not paying for it. I can only add my own feelings on this: what matters is few changes. When you’re on a train, you can relax with a book, or do some work. It doesn’t really matter if the journey is 45 minutes or an hour and a half.
Of course commuters place a much higher value on time than the occasional business or leisure traveller. Which is why High Speed trains drain economic potential out of the regions: people can commute into London from farther away.
The money would be better spent upgrading existing track, rather than on a massive vanity project. But politicians like to cut ribbons on shiny new toys. A longer platform in Stevenage is more use, but less glamorous a photo-op.