LONDON — Britons pay almost three times as much as Americans for gas, and London commuters pay nearly $16 a day just to get into the city. But they do have their limits.A transport ministry proposal last year for a road congestion charge that could see drivers pay up to $2 a mile has sparked an online revolt, with motorists crashing part of the British prime minister’s website Monday night in a barrage of protests.

“We’ve seen a succession of governments look at drivers as a source of public revenue,” said Mark McArthur-Christie, a director of the Association of British Drivers, a motorists’ lobbying group. “But I think the government pushed things one too far.”

Like other countries in Europe, Britain has been trying to balance its environmental commitments against the challenge of increasingly clogged roads.

Britain’s transport ministry predicts that congestion across the country will increase by a quarter between 2000 and 2010, costing Britain some $23.4 billion in economic losses. While other alternatives are being considered, road charges of some kind are inevitable.

A study commissioned by the government last year said road charges could cut congestion in half, saving the British government billion of dollars a year by 2025. It said motorists might end up paying as much as $2 per mile for travel on busy roads.

But the cost to motorists, combined with a proposal to track them using a satellites to determine the charges, has sparked a popular revolt. One driver, Peter Roberts, was irritated enough to advertise his grievance on Tony Blair’s website, which invites members of the public to petition the prime minister.

The part of the site that accepts e-petitions crashed Monday evening as drivers rushed to add their names to the tens of thousands of electronic signatures garnered by Roberts’ appeal late last week. So far, 1.3 million names have been logged.

“The idea of tracking every vehicle at all times is sinister and wrong,” Roberts wrote. “Road pricing is already here with the high level of taxation on fuel.”

Britain’s heavily taxed gasoline sells for an average $6.34 per gallon, according to Catalist Ltd, which tracks prices at British pumps. London commuters pay a $15.60 congestion charge daily — a fee enforced by cameras that snap pictures of license plates.

Drivers’ resentment over the charges is driven partly by a perceived loss of freedom, said Jennifer Bird, who has studied public attitudes toward road charging for the Institute for Public Policy Research in London.

She said that the majority of Britons acknowledge that congestion is a serious problem, even as she cited government statistics saying that the price of driving a car has fallen in absolute terms since 1980.

Environmental campaigners threw their support behind the Blair government.

“The biggest transport problem we face is not congestion, it is climate change,” Friends of the Earth’s London office said in a statement. “Emissions from transport are growing and tough action is urgently needed to tackle them.”

Britain is not the first country to consider an electronic road charge. Last month the incoming Dutch government pledged to introduce a “kilometre tax” within four years to replace a current road tax and a tax on new cars — bringing forward the date slightly from the planned 2012.

The Dutch Ministry of Traffic and Waterways said the price had not yet been determined.

Blair’s e-petition website, meanwhile, was still sluggish yesterday evening.