Growing passenger numbers have already led to a crisis of capacity at Birmingham New Street station.
The National Audit Office has warned that growth in demand for rail services on the West Coast Main Line will lead to the route running out of capacity as soon as 2015.
But New Street station cannot cope with the passengers it already has. It serves 31 million passengers a year – so many that platforms have been shut down 15 times in the last year because of dangerous overcrowding.
As the heart of the nation's rail network, difficulties at New Street affect train services in London, Manchester, Glasgow and Edinburgh.
And the congestion is only going to get worse when new franchises come into effect in November 2007.
Changes to the Cross Country franchise mean that a number of long-distance services passing through Birmingham will now terminate there.
Passengers will be expected to continue their journey by changing at New Street – putting extra strain on the station.
As the National Audit Office report makes clear, passenger numbers have also grown because services have improved.
Before September 2004, the journey from Birmingham to London took one hour 39 minutes. Now it takes one hour 21 minutes, and by December 2008 this is expected to have fallen to one hour 18 minutes.
Punctuality has improved, and Virgin Trains has introduced classy Pendolino vehicles – the so-called tilting trains.
As a result, passenger numbers have grown by 20 per cent in one year, and freight traffic is also up. It shows the urgency of rebuilding New Street.
The National Audit Office suggests one method of increasing capacity would be to add carriages to trains. Again, this would require improvements to the station.
An ambitious #500 million "Birmingham Gateway" scheme to rebuild New Street has won the backing of Network Rail, the City Council, Virgin Trains, Centro and all the city's MPs.
A Department for Transport review concluded in July that the Birmingham Gateway plan was viable. However, a firm decision on whether to back the scheme may not come until next summer.