Image copyright Thinkstock Image caption Some 12 million cars are predicted to be on the road on 23 December

With 12 million drivers on the roads, 200 sets of rail engineering works and airports full of people jetting off to spend Christmas abroad, it will be busy however you travel over the festive period. But what kind of transport should you really avoid - and when?

1. When to stay off the roads

Christmas Day falls on Sunday in 2016. The last time this happened was in 2011, which leads experts to suggest one of the busiest days on the roads will be Friday 23 December. Another of the busiest days has already been and gone, which was Tuesday 20 December.

According to traffic information company Inrix, some journeys may take twice or even three times as long compared with other times of the year.

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According to the AA, 12 million cars will also be travelling at least 20 miles on Friday 23 December.

The AA worked this out based on a survey of 19,317 members, 41% of whom said they would be making long journeys that day. It then applied the figure to the number of vehicles in the UK.

Highways England has promised to complete or lift 448 miles of roadworks from Friday until 3 January.

During this period, Tuesday 27 December has been identified as a day to avoid the roads with many people travelling home after the Christmas break.

2. When to avoid the trains

Image copyright PA Image caption Rail engineering work begins on Christmas Eve

The Southern conductors' strikes will be followed by rail engineering work, set to start on Christmas Eve, Saturday 24 December.

That means people will need to check whether they should travel on the Friday or before if they want to avoid disruption.

London based private hire company Addison Lee expects Friday 23 December will see double the number of people try to get to rail stations compared with a normal weekday.

The usual shut down of rail services on Christmas Day offers a chance for engineers to carry out maintenance and upgrade work.

And because it's a quieter time for people travelling in general, the period between Christmas and New Year will also mean planned work will hit services.

Travelling to and from airports Changes to rail services Heathrow No services to and from London Paddington 24 to 29 December Stansted Express Replacement buses from Liverpool Street, 31 December and 1 January

Gatwick Express Saturday service from 27 December to 30 December and 2 January

Manchester Airport Disruption on various routes 21 December to 2 January Getty Images

There are 200 railway engineering projects, including:

Engineering work between London Waterloo and Clapham Junction will close various lines on Christmas Eve.

Paddington Station will be closed from Saturday 24 December. All lines will be closed between London Paddington and West Ealing between 26 and 29 December, with no Heathrow Connect or Heathrow Express services to or from Paddington.

Work between Manchester, Eccles, Salford Crescent and Trafford Park will affect services over Christmas and until 2 January 2017.

Arriva Trains Wales services between Manchester Piccadilly and Warrington Bank Quay will be replaced by buses. Manchester Oxford Road and Deansgate stations will be closed to trains on 27 December and from 31 December to 2 January.

Northern trains between Manchester Airport, Blackpool North and Barrow-in-Furness are being diverted, running from Manchester Victoria instead.

Virgin Trains is running a reduced service to and from Manchester Piccadilly on New Year's Eve.

There will be bus replacement services in place between Cardiff Central, Bridgend, Newport and the Valleys from 27 December until 3 January.

3. And the airports?

About 223,000 people will depart from and arrive at Heathrow Airport on Friday 23 December, compared with about 200,000 on a normal day.

British Airways cabin crew have voted for strikes in a dispute over pay and conditions. They will walk out on Christmas Day and Boxing Day and the action could involve up to 4,500 staff, but BA says it will still run flights.

And Virgin Atlantic pilots have voted for industrial action short of a strike in a row over union recognition. The Professional Pilots' Union (PPU) said "pilot goodwill" will be removed from 23 December. Virgin said it did not expect flights to be affected.