Britain was braced for the start of a three-day protest against high fuel prices, with the government and police vowing to keep supplies moving if demonstrators try to block them.
Police chiefs said they would not allow protesters to obstruct roads leading to oil refineries - a tactic which brought Britain to a standstill during similar protests in 2000.
Organisers have been wary of giving details of their plans and the only confirmed protest is a go-slow on Friday on an 80-mile stretch of motorway in south Wales.
"The police will take firm action as necessary," said Chris Fox, President of the Association of Chief Police Officers. "Blocking the highway or preventing companies going about their business is unlawful."
He said fuel would only run short if motorists were panicked into buying excessive amounts of petrol.
Drivers queued for fuel at some filling stations yesterday as fears grew that oil supplies might be disrupted, although retailers said there were no problems yet and urged customers not to panic.
Protesters want the government to lower fuel prices by cutting taxes. Finance minister Gordon Brown has ruled that out, telling Sky News TV on Tuesday: "British people understand very clearly that the source of this problem is a doubling of world oil prices."
The cost of a liter of petrol climbed above 1 pound in some areas last week after the price of oil on world markets hit a record of more than $70 a barrel.