While some are taking to the air to travel to Mediterranean hotspots, anyone getting the car out in the UK will have to compete for road space with an estimated nine million other vehicles.
On the railways, engineering work includes major work at London Bridge station and at Watford in Hertfordshire.
The estimate of more than two million going abroad comes from travel organisation Abta, which said that Spain and its islands as well Greece, Turkey and Tunisia were among the most-popular destinations.
Favourite spots for those going further afield include Florida and Cancun in Mexico, while the most popular city-break destinations include Paris, Amsterdam and Barcelona.
Around 500,000 passengers are expected to depart from Heathrow airport over the weekend, as well as 234,000 from Gatwick, 172,000 from Manchester, more than 150,000 from Scotland’s airports and 134,000 from Stansted.
An expected 78,000 will leave from Luton, 72,000 from Birmingham, 47,000 from Bristol, 42,000 from East Midlands, 30,000 from Leeds Bradford and 7,000 from Bournemouth.
In addition, hundreds of thousands will also be leaving the country from other regional airports, ports and the Channel Tunnel.
Abta said domestic bookings had been boosted by the recent heatwave, although those holidaying in the UK will be getting cooler temperatures than during the long, hot spell as well as the possibility of some rain.
Abta chief executive Mark Tanzer said: “This weekend is set to be one of the busiest of the year as we see lots of holidaymakers heading off for the bank holiday weekend.
“While a holiday budget will go further abroad this year thanks to a strong pound, we are also expecting lots of people to enjoy the long weekend at home.”
On the railways, a nine-day part-closure of London Bridge station begins on Saturday, with no First Capital Connect or Southern trains calling at the station until September 1. The changes will allow Network Rail to carry out a huge programme of work as part of the £6.5 billion Thameslink project.
The Watford work will mean disruption on the West Coast main line.
The RAC said it expected Saturday and Sunday to be the busiest days on the roads, especially as there are major music festivals at Leeds and Reading in Berkshire.
VisitEngland said 5.1 million Britons were planning an overnight holiday trip in the UK this weekend, with four million planning on taking an overnight trip in England. This was likely to generate some £1.2 billion in tourism spending for the UK economy, £940 million of which will be spent in England.
More than half a million people will fly with British Airways over the weekend. The airline will operate 4,000 flights and will serve nearly 10,000 bottle of champagne on board, with more than 400,000 meals served.
The Highways Agency said around 164 miles of roadworks on England’s motorways and major A-roads would be completed before the weekend and 110 miles of works will be suspended between Friday and Tuesday (August 26).
But for safety reasons a number of roadworks will have to stay in place, including some on the M1, M5 and M25.
National Express said it had seen a surge in coach bookings for the bank holiday, with bank holiday Monday expected to be its busiest day.
It added that London was the most popular destination for coach travellers this weekend, followed by Birmingham and then Heathrow airport.
Meanwhile, a survey from Sainsbury’s Bank Travel Insurance showed that 18% of people have been on “3G” holidays (trips involving at least three generations of a family) in the past year.
The eldest generation were the most likely to cover the cost of such holidays, followed by the middle generation.
Tourism Minister Helen Grant said: “The bank holiday weekend is set to be a bumper one for domestic tourism, generating over £1 billion in spend for the UK economy.
“From city breaks to days out on the coast, world-class music events to cultural trips, the UK has something for everyone to enjoy.”
A spokesman for rail industry body the Rail Delivery Group said: “While we understand there is never an ideal time to carry out major work to maintain and improve Europe’s fastest-growing railway, the industry works together to carefully plan improvement schemes to minimise disruption for passengers.
“Work goes on every day to deliver thousands of vital but smaller-scale improvements and over the next five years billions of pounds will be reinvested in the railway to meet rising demand for even better, faster and greener services.”