The great Christmas getaway has begun with schools breaking up for the festive period.
The AA said it expected up to 18 million cars will take to the roads over the holiday period, with Thursday December 22 and Friday December 23 likely to be the busiest days.
Around 4.25 million people are travelling abroad for Christmas and the new year, while those staying at home will have to put up with engineering work on some rail routes.
A drivers' strike on London Underground is also likely to affect Boxing Day Tube services.
Wintry weather on Friday generally led to wet, rather than snowy, conditions. But the AA warned drivers to prepare for unsettled weather.
It predicted that getaway traffic in the run-up to Christmas was likely to be heavy on major routes, including the M1 in Buckinghamshire and Bedfordshire, the M4 between London and Newbury in Berkshire, the M25 around London, and the M4 and M5 in the West Country.
A recent AA/Populus survey of 16,647 AA members found that 68% were planning to stay at home this Christmas, with people in north-east England (78%) most likely to stay put and Londoners (60%) least likely to.
More than a quarter (26%) will be hitting the road to spend Christmas away from home, with 10% racking up more than 100 miles.
Keith Miller, AA patrolman of the year, said: "Although the current weather forecast for Christmas isn't as bad as last year, the outlook is still quite unsettled which means road conditions can be unpredictable.
"The Christmas period is always busy, so allow extra time for your journey and keep a close eye on weather and traffic reports before departing."
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