Motorists are urged to allow plenty of time for journeys over the bank holiday weekend and school half-term break.
The RAC forecasts that around 20 million drivers - over 70% of the country's motorists - are planning to take to the roads.
Four million drivers are set to get behind the wheel on Bank Holiday Monday alone with the RAC warning there could be even more if a threatened rail strike goes ahead.
It says Friday and Saturday are also likely to be very busy, even though Highways England is in the process of removing 400 miles worth of roadworks before the rush.
Nevertheless, officials are advising motorists to plan their trip with the RAC route planner , give themselves extra time and think about avoiding peak times.
RAC spokesman Simon Williams said: "The threat of a major rail strike is looming heavily over the nation's drivers who will be waiting to find out if the thousands of people who were planning on making a trip on the train switch to the road instead. If the strike does go ahead, it's likely to add to the jams that we're expecting on many of major routes.
"As always, the advice is to plan ahead and not be too surprised if you encounter some queues if you're driving any serious distance this coming bank holiday."
The RAC's traffic line can be accessed from a mobile on 64644, while iPhone and Android users can download the RAC App to stay abreast of the latest traffic conditions.
Copyright Press Association 2015