In some cities, petrol and food deliveries were reduced and car factories laid off workers because lorries carrying parts could not get through.
Politicians and commentators condemned the action as 'hostage-taking' or 'ransom' and the goverment showed signs of growing irritation.
The protest, against a new driving licence system which will bring France into line with many of its neighbours, looked as though it was dissolving when the government offered some concessions on Wednesday night. Jean-Louis Bianco, the Transport Minister, agreed that recording equipment installed in cabs would not be used retroactively to catch drivers for speeding.
Police monitoring disks discs taken from cabs could use them as evidence. With the new 'points' or endorsement licensing system introduced on Wednesday, lorry drivers argued that this put them at a disadvantage compared with private motorists, who have to be caught red-handed. Immediately after the agreement, the 1,000 trucks at Nemours on the A6 Paris-Lyons motorway started to move.
Paul Quiles, the Interior Minister, said after the Nemours blockade began to weaken that he was confident the blockages would disappear by the end of the day. When they did not, Pierre Beregovoy, the Prime Minister, repeated a threat made by Mr Quiles on Wednesday to suspend the driving licences of protesting drivers.
One after another, government officials condemned the protests but there was little they could do. In the case of the more usual farmers' protests, where only a few dozen vehicles are used, riot police fire tear-gas to clear the roads. In the latest case, where hundreds of vehicles are involved, the only effect of similar tactics would be to make the drivers run out of range, leaving their lorries still blocking the highways.
Around the northern city of Lille, drivers cut access from the Channel ports and the Belgian frontier. The progress of tourists from Britain, Belgium and the Netherlands will be affected if the protest continues into the weekend, when the first rush of the summer season is expected. At Caen, in Normandy, the road to Paris and the south was cut. In Lyons, petrol was in short supply, and Michel Noir, the city's mayor, appealed for government help, citing public health reasons. Both Lyons and Toulouse were almost totally cut off.
Roadblocks near Avignon cut access to the Spanish Costa Brava and to Marseilles and Italy. The situation was aggravated by farmers protesting against reform of the EC Common Agricultural Policy, who cut the main Paris-Nice rail line near Avignon. Even Paris began to feel the pinch as drivers changed their tactics by besieging petrol distribution depots. A few petrol stations ran dry. Wholesalers at the food market at Rungis, south of Paris, said that some products were not getting through. The situation was similar in many other parts of the country but there was no hint that the shortages were yet critical.
Many of the foreign lorry drivers seemed resigned to the blockades, although there were reports that a Belgian had threatened to set fire to his vehicle. One Irishman carrying beef started selling his load to provide steaks for protesters.