UK weather: Many of Britain's roads, railways and runways at standstill as snow chaos continues

Travel disruption ongoing as extreme cold, high winds and blizzards from Storm Emma cause commuter havoc

The fourth day of extreme cold across the UK began with even more travel disruption. Roads in South Wales, the south and south west of England and the Pennines have been closed, with hundreds of cars stranded overnight.

In Wales, the main route across the centre of the country to Aberystwyth is blocked, and there are problems with the A40, the A470 and the A458.

The A303 across Hampshire, Wiltshire and Somerset has been at a standstill, with motorists sleeping in their cars. The A31 is also blocked, and there are problems on the southern end of the M5 and the A35, which runs parallel to the east Devon and Dorset coast.

The A46 between Bath and the M4 is closed. Close by there are problems with the second Severn crossing.

South of Birmingham, the M40 southbound is closed between junctions J14 and J12 because of a collision and is likely to be blocked for much of the rush hour.

The M1 is experiencing problems between Milton Keynes and Northampton.

The M62 across the Pennines is suffering between junctions 21 and 22. Two other trans-Pennine routes in northern England, the A628 and the A66, are closed

In Scotland, the Forth Road Bridge is closed, and the M9 north of Stirling is blocked to southbound traffic.

Most train operators have sharply reduced their services, with Arriva Trains Wales cancelling all services except the North Wales line. The train operator said: “Following further deterioration of weather conditions overnight, and despite considerable effort by railway, unfortunately both Arriva Trains Wales and Network Rail have had to take the difficult decision to cancel all services in the southern part of Wales.

“As a result, customers are advised not to attempt to travel.”

The company running trains west from London Paddington, GWR, warned: “Train services will start later than the normal timetable today and some lines may not start at all. The advice is not to travel. If you start your journey, Great Western Railway can not guarantee that you will get to your destination.”

South Western Railway has closed the lines across Somerset, Wiltshire and Dorset from London via Salisbury to Exeter, and from Bournemouth to Weymouth as well as a number of commuter lines in and out of London Waterloo.

The weekend has arrived early in the Greater Anglia region, with a Saturday service on the Norwich-London line and Sunday schedules from Cambridge to the capital.

The train operator Northern says severe disruption is being experienced on all routes. The advice is to only travel if absolutely necessary. Routes involving the Pennines are all closed.

Later this morning - after the rush hour - ScotRail will start services between Edinburgh and Glasgow and north from the capital to Dundee.

Ryanair and easyJet have said they will not start operations at the Scottish capital until the afternoon, though Jet2, Flybe and British Airways may begin earlier.

The largest number of cancellations is at Heathrow, where British Airways has cancelled almost 200 flights so far – about a quarter of its normal schedule. Air France, Lufthansa and United Airlines have cancelled multiple flights, and some inbound services from Singapore, Johannesburg and Dubai have been grounded.

BA is telling passengers: “If you are due to travel on any short haul service up to and including Tuesday 6 March, regardless of whether your flight is currently showing as operating or not, you can rebook your flight to a later date and travel on dates up to and including Wednesday 21 March.

“In addition, if you are due to travel on a long haul service to or from London Heathrow up to and including Sunday 4 March, regardless of whether your flight is currently showing as operating or not, you can rebook your flight to a later date and travel on dates up to and including Wednesday 21 March.”