This year's festive getaway may be less congested than usual - because Christmas falls on a weekend.
The RAC says trips to spend Christmas Day with friends and family could be spread out because of the 2016 calendar.
It estimates that some 3.5 million leisure journeys will be made on UK roads on Friday, with 3.8 million on Christmas Eve and 3.5 million on Christmas Day.
Between 4pm and 8pm is expected to be the busiest time over the festive period, as motorists embarking on the Christmas getaway battle for space with regular Friday evening traffic as people drive home from work.
The figures were based on a survey of 1,546 motorists.
RAC traffic spokesman Rod Dennis said: "Unlike in recent years, we've got a significantly extended Christmas getaway this year.
"With Christmas Day on a Sunday, and with most schools having broken up on December 16, it means many more drivers this year have a chance to space out their Christmas getaway journeys.
"The fact we have a lengthy pre-Christmas stretch this year is not to say there won't at times be heavy traffic on the road network through the week, perhaps peaking on the 23rd when many workers finish for Christmas and leisure and commuter traffic take to the roads together.
"But we're hopeful things won't be quite as pressured on our motorways and major A-roads this year as they have been before."
Rail passengers face disruption, with the annual festive shut down meaning no trains will run on Christmas Day, with only certain services on Boxing Day.