A proposed nationwide pay-as-you-go road charge has already prompted a strong reaction from transport experts and campaigners.
Congestion is predicted to get worse
Variable charges of up to £1.43 a mile - in busy routes in rush hour - could replace road tax and fuel duty under the government's plans.
Transport experts said it would be the world's most advanced road pricing scheme - but predicted political and technical difficulties in bringing it in.
'Poll tax revolt'
"Governments will upset at their peril society's wish to do what it wants to do and that is to move around," says Professor Garel Rhys, director of the Centre for Automotive Industry Research at Cardiff University's business school.
Terence Bendixson, secretary of the Independent Transport Commission (ITC) at the University of Southampton, says there "could be a poll tax revolt if Alistair Darling fails to deal with these issues in ways that drivers see as fair and reasonable".
And Bert Morris, director of the AA Motoring Trust, said: "It's feasible, the question is, is it politically acceptable?
"Will people affected think they are better off or worse off?"
Transport also has a wider impact on other parts of the economy, Mr Morris points out.
"Tourism is transport reliant. What will be the impact on tourism of road pricing? Will people stop taking day trips to the seaside because of it?"
Mr Darling is set to outline the proposals fully in a speech to the Social Market Foundation on Thursday.
Mr Darling is proposing to replace road tax and petrol duty
There are currently about 30 million vehicles registered in the UK, up from 20 million just 15 years ago.
Building extra roads to tackle congestion does not work and governments had realised this, said Professor Rhys.
The government could use the pricing scheme to indicate where roads are most needed, he said.
"I think the government will have to show this is not just simply a system of charging for the existing road network, soaking the people who are using it, but also use it as a price signal where it will show where new roads are really needed," he added.
He said many of the current areas of congestion could be due to roadworks or accidents.
"I also think policing the proposed scheme will be a major problem. The vast majority will be law-abiding but what about the minority? There could be a sizeable one."
Experts say other potential problems for the government include the effect on low income drivers, the reliability of the new technology, and deciding how to administer the collection of funds.
Tony Grayling, assistant director of the Institute for Public Policy Research and a former adviser to the government, also warned of more pollution and traffic in rural areas.
"Whilst you would be reducing traffic in urban areas at peak hours, that would be more than outweighed by the growth in traffic in rural areas, where you had made motoring cheaper by cutting fuel duties," he says.
Sue Nicholson, head of campaigns for motorists' group the RAC Foundation, says the proposal, which would start with a pilot scheme, was a potential solution to the increasing traffic congestion.
"It's certainly worth talking about. It's potentially a way forward out of the congestion problems that we face," she says.
"Providing this tax was substitutional to fuel tax and road tax rather than additional and provided we had some other guarantees then I think, for a lot of people, this would be a tempting option."