LONDON, Dec. 22 (Xinhua) -- British motorists face delays of up to two hours on the country's busiest motorways on Friday as more than 20 million vehicles take to the road for Christmas, which falls on Monday this year.

Chaos was reported as the final working day of the year combines with a surge of last-minute Christmas shoppers and the festive getaway.

Drivers have been urged to avoid roads during the evening rush hour.

An estimated 1.3 million drivers on leisure trips are fighting for road space with regular commuters on the last working day before Christmas.

Highways England is due to suspend more than 640 kilometers of roadwork on motorways and major roads from Friday to increase traffic flows.

Highways England reported 46 traffic incidents on motorways and major A-roads at around 1pm, including 15 classed as severe.

A 6.4-kilometer traffic jam with thousands of drivers built up after a lorry turned into a fireball and added to the Frantic Friday mayhem this morning.

A sheet of flame six-meter-high enveloped the driver's cab and the front of the 12-meter long delivery lorry on the southbound carriageway near junction 9 on the crowded M40 near Bicester, Oxon in southeast England.

National Express, the coach operator, is running its largest Christmas schedule to meet increased demand from cities such as Bournemouth, Cardiff, Leeds, Edinburgh, Portsmouth, Britol, Glasgow and Manchester.

The traffic data company, Inrix, said that the worst non-accident traffic black spot on the Friday before Christmas last year was the A303 at Stonehenge.

There were tailbacks for more than 11 kilometers when congestion at the notorious bottleneck peaked shortly after 1800 GMT on Dec. 23, 2016.

However, congestion will be made worse by large parts of the rail network being shut down for engineering work, with 260 updates planned.

The west coast main line will be out of action between Preston and Lancaster over Christmas and further disruption is expected around London and Manchester.