By Nick Assinder BBC News Online political correspondent

So Alistair Darling has confessed that the government has failed to unblock Britain's roads.

The transport secretary has told MPs that there had been more traffic in 2000 than anyone had thought.

Combined with higher than anticipated growth: "the forecasts made two years ago almost certainly underestimated the future levels of congestion we are faced with."

As understatements go that must rank up there with describing the Cultural Revolution as a little local difficulty.

His admission came as he gave an update on the government's 10 year transport plan aimed at putting some �180 billion into transport by 2010.

His statement was greeted with ridicule by the Tories with shadow spokesman Tim Collins declaring the plan was now "so much of a corpse that Amanda Burton has been spotted preparing a post mortem".

And, as far as most commuters are concerned the country's highways might as well be run by NCP.

Darling admits failure

Conspiracy theorists may even speculate that John Prescott's post-1997 claim that he wanted to get people out of their cars was actually being put into practice by stealth.

Trouble is, the moment commuters do abandon their cars they face even more misery as they wait for trains and buses that will probably be late or never turn up at all or, if they do, will be overcrowded and filthy.

Mr Darling's excuse is that nobody foresaw just how bad the problem was when they made all those election promises, or since.

Heady days

He has even claimed previously that the Hatfield rail disaster - which has meant switching investment away from services to safety - could not have been predicted.

Frankly, with the state the rail infrastructure was clearly in, it is a scandal nobody did predict it.

The truth is, no one believes the task of ending gridlock Britain is an easy one, or can be achieved in anything under decades.

No end in sight

It was hugely optimistic for ministers to have made the claims they did back in the heady days of 1997 and after.

And, like Chancellor Gordon Brown's predictions for growth which he has been forced to revise this year - many suspect the dodgy optimism was deliberate.

What is certainly true is that successive transport secretaries have failed to convince voters and travellers that they have got a grip of the issue.

Two Jags

It is also true the problem was largely due to decades of governments deliberately ignoring it.

Ministers knew if they ever stepped into this particular quagmire the chances were they would get sucked down by it. Probably best to leave it alone.

At least Labour moved it up the agenda. But, in doing so, it made a rod for its own back.

Macdonald parachuted in

First Transport Secretary John "two Jags" Prescott could not seem to make up his mind whether to get people out of their cars or build more roads. And, of course, there was the Heathrow bus lane.

His reign was deemed such a failure that Tony's friend Gus Macdonald was parachuted in over his head to get a grip.

Then it was the ill-fated Stephen Byers who had so much bad news to bury he just could not find enough days to do it on.

When he finally quit over the Jo Moore scandal, he was replaced by Alistair "Safehands" Darling who spent the first few months of his reign keeping his head down.

Much was, and is, expected of him. He will have to produce visible improvements before the next election if he is to go down as a success and save the government fresh embarrassment.

But they way he and his bosses are talking at the moment, it looks like they are preparing commuters for a much longer haul ahead than that.