WHEN a high-speed rail link between London, Birmingham and Manchester was announced in 2009 all three big political parties cheered. Even UKIP, which might have been suspicious of such a grand projet, had plans for it in its 2010 manifesto. The line, known as HS2, was expected to create jobs, particularly in the north. Nearly five years on, though, criticism is growing. HS2"s budget has swelled. The National Audit Office has questioned the business case for it. A former business secretary and a former chancellor have both withdrawn their support. Advocates are now leaning heavily on one justification for the line. A new, quicker railway is needed to avoid a "capacity crunch," says Rupert Walker of Network Rail, the company that owns Britain's tracks. This crunch is particularly painful on the West Coast main line, which runs from London to Scotland via Birmingham. The line is Europe's busiest mixed railway and carries a quarter of all freight, points out Mr Walker. Railway capacity is indeed a growing problem. Between 2002 and 2011 passenger journeys recorded by long-distance operators grew by 62%, more than on regional networks or on those around the capital. The number of trains increased more slowly than the number of passengers, so people are more squeezed. And rail freight grew by 16% between 2002 and 2012. The question is whether such rapid growth will continue. There are reasons to think it will not. The rate of growth on long-distance passenger journeys already appears to be slowing down. Whereas between 2011-12 and 2012-13 the number of journeys in London and the south-east increased by 3.9%, long-distance journeys grew more slowly, by 1.9%. Journey numbers on the whole network in the fourth quarter of 2012-13 fell slightly compared with the previous year. Although many more people are taking the West Coast main line, the number of miles they travel seems to be tailing off. Between 2009 and 2010, just after the line was upgraded, passenger miles jumped by 20%. That growth has not been sustained. Between 2011 and 2012 passenger miles increased by 4.6%; between 2012 and 2013 they edged up just 0.9%. The future path of growth "is the great bet," says Arthur Leathley of Virgin Rail, which runs the line - in other words, it is uncertain. And the West Coast main line is not the most congested. None of its services made the list of the ten most overcrowded peak train services in England and Wales in 2012. Several trains run by London Midland, the cheaper, slower service to Birmingham, did. Euston, where West Coast trains pull in, has fewer packed trains than other London stations (see chart). Christian Wolmar, a transport writer, worries that there is no guarantee passenger growth will continue apace. And if people shift to taking HS2 between big cities, some smaller routes may require extra subsidy to chug along, increasing costs further. Others claim that capacity can be increased more easily and cheaply. If the number of first-class carriages were reduced and trains were extended to 12 carriages, most peak congestion could be dealt with, argues 51M, a campaign group. By most European comparisons British trains are already pretty speedy. They would be more so with better signalling and more electrified tracks. Better management and more subtle ticket-price differentiation could reduce congestion. Politicians love cutting ribbons. But HS2 increasingly looks like an expensive answer to a problem with several solutions.