A substantial number of new roads could be built if the government introduced "pay-as-you-drive" charges on Britain's roads, research suggests.
Roads around cities are under increasing traffic pressure
The Independent Transport Commission said enough money would be raised to put roads in tunnels in built-up areas.
It said the charges would have to be relatively high to cut congestion, but could be lowered with the building of new roads to ease jams.
The suggestion of building more roads is likely to anger environmentalists.
BBC transport correspondent Tom Symonds said pay-as-you-drive road charges were now firmly on the government's agenda.
New roads would be most beneficial on the edges of towns and cities, where traffic pressure was growing fastest, our correspondent said.
The proposed building of roads in tunnels in certain areas is about six times more expensive, but more environmentally acceptable.