Mr Darling's scheme shows the road forward

This government often talks the talk when it comes to radical measures but it doesn't always walk the walk. All the more surprising and welcome, therefore, that the Transport Secretary, Alistair Darling, is pressing ahead with a truly innovative scheme aimed at banishing the threat of gridlock enveloping Britain's roads.

This government often talks the talk when it comes to radical measures but it doesn't always walk the walk. All the more surprising and welcome, therefore, that the Transport Secretary, Alistair Darling, is pressing ahead with a truly innovative scheme aimed at banishing the threat of gridlock enveloping Britain's roads.

What it boils down to is abolishing fuel tax and, possibly, road tax as well, and installing a pay-as-you-drive system. This means that drivers would pay a small fortune to drive round the M25 in the rush hour but little or nothing to bumble down a country lane at 3am on a Sunday morning.

The technology involves planting a little box in every vehicle that would monitor where, when and for how long the vehicle was on the road and charge accordingly. The proposed sliding scale of charges would range from around 2p per mile to £1.34.

There will be a mass of objectors to the scheme, of course, ranging from commuters who fear they may end up paying far more than they do now, to civil libertarians who will, no doubt, have much to say about the prospect of boxes in their vehicles monitoring their movements. Some scoffers will pronounce the technology unworkable and point to the fact that no other country has yet tried to implement a road-pricing scheme nationwide.

The most cogent argument made about the proposal has come from environmentalist groups who claim it will act as a disincentive to drivers who contemplate trading in their gas-guzzlers for environmentally friendly vehicles. The substance of their complaint is this: heavy fuel taxes on petrol act as a spur to all but the super-rich to buy cars that consume less petrol. Scrap the fuel tax and road tax, so this argument runs, and there isn't that much point in investing in, for example, an emission-free Reva G-Wiz, an electric Indian-made car that is now making modest sales in Britain, mainly in the London area.

It is true that the present plans do not appear to have an answer to this. But this is surely only a temporary obstacle. If the technology exists to install these boxes in the nation's cars in the first place, we can presumably also come up with graded tariffs, whereby the cars consuming most fuel would pay more.

The bald fact is that the number of cars registered on the roads already stands at around 25 million and is set to rise remorselessly in coming years. At the same time, the motorways are already carrying five times more cars than they were designed to. Most studies agree that once the number of cars hits the 40 million mark, there is likely to be near-permanent gridlock in many urban areas. Building more lanes and roads has become part of the problem, not the solution. Something drastic must be done and a debate of this kind is certainly a welcome step.