John Prescott's £180bn plan for public transport runs into an instant problem with the travelling public. No one believes big figures any more. We have been drowning in numbers while the nation's roads and railways have been deteriorating under our feet.

The new figure differs from previous ones only in that it is bigger and stretches farther into the future. It is a mixture of public and private money and includes projects now being built - like the fast rail link from the Channel - as well as others unannounced. The plans are huge, but mainly because previous ones have been as badly delayed as the trains while ministers dithered over whether to confront motorists and how much public money they ought to put in.

The new package should be judged against two criteria. First, whether it delivers measurable and cost-effective solutions. Some proposals - like a 5% reduction in road congestion over 10 years - will be difficult to judge even if successful. Others - like cutting the London to Edinburgh journey to three hours 30 minutes - can be easily checked against delivery.

Second, where extra public money is being invested it should bring a proper return on capital for the investor - the taxpayer. It is very welcome that the extra £7bn allocated to rail should be funnelled through the parsimonious hands of Sir Alastair Morton, head of the Strategic Rail Authority. But it should not end there. This is public money, and there is no case for it being used in a way which is going to enrich Railtrack and the operating companies. They have already profited outrageously from assets bought at fire-sale prices when the Conservatives rushed privatisation through to beat an election deadline. The sum of £7bn is more than twice what the taxpayer got from privatisation. Rail companies must make decent returns - but not excess profits at the taxpayer's expense. There is a strong case for demanding an equity stake in exchange for public money.