Easter traffic is expected to peak later today at the start of a four-day holiday period that will see 20 million car journeys.
About 6.6 million Britons are planning a trip involving an overnight stay over the weekend, according to tourism body Visit England. That is up from six million last year.
The worst time to travel on the roads is expected to be between 4pm and 6pm today, when traffic will be about 28% above the average for those hours, according to Inrix, which provides traffic information.
On major motorways, some journeys could take three times longer than usual, the group said.
Highways England has told drivers to consider alternative routes and allow extra time for their journeys.
Motorists driving between junctions 9 and 21 on the M25 should expect delays of up to 90 minutes, while those heading in both directions on the M6 and southbound on the M5 towards the West Country could have delays of an hour.
By contrast, Easter Sunday will be the quietest day of the period, with 25% less traffic compared to an average Sunday.
On railways, services on some routes will be reduced as Network Rail carries out some 200 engineering projects. Trains to London, Manchester, Bath, Edinburgh and Glasgow are affected.
Air travel is expected to be busiest on Good Friday, with Spain the favourite overseas destination for the weekend, according to travel trade organisation ABTA.
Airports will be busy, especially in London as some 425,000 passengers will travel from Heathrow and another 250,000 from Gatwick.
For those who opt to stay at home during Easter, bad weather might spoil the fun, especially in the north of England and Scotland, where temperatures are set to fall to between 11C and 12C (52F and 54F).
Sunny patches and warmer temperatures of between 15C and 17C (59F and 62F) could appear further south.