Drivers setting out on Christmas Eve are being warned they could face severe delays, but it's a case of "so far, so good" according to the RAC.
Spokesman Pete Williams said the busiest time for traffic had passed, but the roads in and around London, the M4 and the M6 were particularly busy.
He said traffic levels had been "pretty steady" over the past few days.
Meanwhile, many rail passengers across the country are facing disruption because of planned engineering work.
Network Rail said vital upgrades would be carried out over the festive period.
According to the AA's live traffic reports, vehicle accidents and a burst water main caused problems for people trying to leave central London by car.
Mr Williams said there had earlier been congestion in the north, around Leeds and Bradford, because of cold weather.
He advised travellers to check their oil, coolant level, tyre pressure and tread depth, and to buy some good screen wash before setting off.
The RAC and Inrix, which provides traffic information, had predicted the stretch of the M1 northbound between junction 21 (Coventry/Leicester) and junction 26 (Nottingham/Ripley) would be the worst for delays.
Fewer commuters than usual were expected to travel on Christmas Eve - many having booked the day off work.
But far more leisure journeys than usual were expected - as many as 2.5 million - with the AA predicting half of all motorists would take to the UK's main roads.
The RAC says the number of leisure journeys over the festive season is likely to peak on Boxing Day with an estimated 6.8 million individual trips.
On the trains, there are 330 sets of rail engineering works scheduled to take place until 1 January.
Network Rail said it would do most of the works when no trains are scheduled to run.
No trains run on Christmas Day and there are only a limited number of services on Boxing Day - but nationwide bus companies National Express and Megabus will operate.
The rail disruption includes:
- All lines to and from London Paddington closed on 24 and 30 December. There will be a reduced service on some routes on 27, 28, 29 and 31 December
- No Southern trains to or from London Victoria until Wednesday 2 January
- No Gatwick Express service until 2 January
- Timetable changes for services to and from Liverpool between Monday 24 December and 1 January, affecting East Midlands Trains, London Northwestern Railway, Northern and Virgin Trains
- Replacement buses between Birkenhead Central, Birkenhead North and Liverpool Central from Thursday 27 December to 1 January
- Replacement buses between Manchester Victoria, Stalybridge, Rochdale and Salford Central on 27 and 28 December and a reduced service between Manchester Victoria and Stalybridge on Saturday 29 and Monday 31 December. Buses will also replace some services to and from Manchester Victoria on 1 January
- In north Wales, Virgin trains will not run to or from Holyhead and Wrexham on Christmas Eve, 27 December and 30 December
- In south Wales, the Severn Tunnel will be closed between Christmas Day and New Year's Day
Engineering works have been scheduled for the festive period because the railway is up to 50% quieter than usual then, said Andy Thomas, Network Rail's managing director of strategic operations.
"While most of the network is open for business as usual, some routes are heavily affected and so we strongly advise passengers to plan ahead."
Meanwhile, flights to and from Gatwick airport are operating as normal after three days of disruption following reports of sightings of a drone near the runway.
At Birmingham airport, flights were temporarily stopped on Sunday evening after a technical fault at air traffic control but resumed later on.
The Association of British Travel Agents said more than 4.7 million people will be going abroad between 18 December and 2 January.