Congestion charging must be introduced across Britain to prevent the country's busiest routes coming to a standstill, experts have warned.
Traffic levels could rise 25% by 2010
They say traffic levels could rise by a quarter by 2010, unless the government charges drivers during peak hours.
The study, carried out for the Independent Transport Commission (ITC), says such a policy could cut road use by a fifth - with knock on benefits for the environment.
It adds to the debate started last week, when Transport Secretary Alistair Darling said school run drivers could be made to pay congestion charges under plans being considered to cut rush-hour traffic.
The report, Transport Pricing and Investment in England, says many roads will regularly suffer severe delays by 2010 if charging is delayed.
It says the government must follow the example of London, which introduced congestion charging four months ago and has seen a 16% fall in traffic.
In return drivers should be offered a reduction in motoring taxes, the report says.
HAVE YOUR SAY
It is very unreasonable to introduce congestion charges when our public transport is the laughing stock of Europe
And the billions of pounds raised each year should be used to improve other transport.
ITC head Sir Patrick Brown said drivers would not be "penalised" under a congestion charge, and he said less traffic would mean better public transport.
"In 10 years time there will be real gridlock on the roads if nothing else is done.
"You can have massive improvements in the public transport system in the sense of buses if you make the roads uncongested.
"At the moment people don't get on buses in the cities like Birmingham and Manchester because they are slow unreliable and they don't provide a service.
As we have noticed in London in the congestion charging zone, the buses run beautifully
Sir Patrick Brown
Independent Transport Commission
"But as we have noticed in London in the congestion charging zone, the buses run beautifully."
The report warns that "growing traffic is outstripping road capacity".
The authors say they do not know how much the congestion charges should be.
One option is for all drivers to pay to use the roads in proportion to the contributions of their vehicles to congestion.
Those travelling at peak times and in notoriously busy areas would pay the most.
The report says traffic speeds would rise in the cities and their suburbs as a result, although there would be little change in the countryside.
It says car use in cities would fall, while delays and environmental damage would ease and pressure to build new roads would wane.
There are a lot of other things that need to be done, but some element of this is inevitable because we can't carry on as we are
Stephen Joseph, director of campaign group Transport 2000, welcomed the report's findings.
He said: "Something like a congestion charge is inevitable.
"There are a lot of other things that need to be done, but some element of this is inevitable because we can't carry on as we are."
Last week the transport secretary said school run drivers could be targeted in an attempt to ease congestion.
Mr Darling said he wants to introduce pay-as-you-drive charges, using satellite tracking devices fixed to cars.