Nearly three million road journeys are expected to be made on Friday as people begin their Christmas getaway, motoring organisations have warned.
"Significant" congestion is expected on major roads, with delays likely on the M25, M6 and M40, the RAC said.
The RAC's Matt Dallaway said travelling in the evening would miss the busiest time on major roads and motorways.
The M49 near Bristol - which links the M5 with the M4 - has reopened after a major gas leak closed the motorway.
"Plan your journey, everyone is a hurry to see their loved ones and friends and family, but please think about when you're going to travel," Mr Dallaway told the BBC.
The RAC says the number of leisure journeys will peak on Boxing Day, with 6.8 million trips.
Mr Dallaway said: "We're at this time of year when everyone is frantically trying to get their Christmas presents done, e-commerce is through the roof so there'll be delivery drivers all over working through to Christmas Eve.
"It's obviously a lot milder this year… so that will take a lot of people to the roads."
Meanwhile, a further drone sighting again disrupted flights at Gatwick airport on Friday evening. The latest sighting at Gatwick came at about 17:10 GMT, but flights resumed less than 90 minutes later.