Holidaymakers are facing hours of delays at the port of Dover due to heightened French security checks.
As the Easter bank holiday weekend getaway began, P&O Ferries warned of two-hour hold-ups in the early hours of Friday morning.
Highways England said there were queues on the A20 and A2 heading into the port, and urged people to plan ahead before travelling.
Ferries were being held open for as long as possible to get people on board.
It comes as the Easter weekend looks set to be one of the busiest in years for travellers.
The Association of British Travel Agents (Abta) has estimated that 2.1 million British holidaymakers will head abroad.
Train stations, roads and airports in the UK are also expected to be extremely busy.
The RAC said drivers were expected to take nearly 19 million separate leisure journeys over Easter, with hot spots set to include the M25 between Gatwick Airport and the M1, the M3 south west of London, the A303 near Stonehenge, the M55 between Preston and Blackpool, and the M53 between Liverpool and Chester.
At the major airports, half a million people will fly out from Heathrow, 260,000 from Gatwick and 160,000 from Manchester.
The Eurostar service from St Pancras will take 70,000 passengers under the Channel and into mainland Europe this weekend, with many headed to the French capital Paris.
In July 2016, hundreds of motorists heading off on their summer holidays were stranded in 12-hour traffic jams at the Port of Dover, with delays blamed on staff shortages at the French border as well as enhanced security controls.