Severe weather is causing major travel disruption across the UK and Ireland.
Road closures, stranded vehicles and cancellations are widespread due to snow and ice.
Services on trains and planes are disrupted, with travellers urged to check with their transport provider before setting off on their journeys.
Police closed large sections of major routes as several roads were left impassable following heavy snowfall.
Drivers are being advised to avoid unnecessary journeys and stick to major routes where possible if they must travel.
The RAC had its busiest day in 10 years on Tuesday with 9,500 call-outs, but believes this figure could be topped on Wednesday as conditions worsen.
The breakdown rescue firm’s road safety spokesman, Pete Williams, said: “For drivers, the first consideration is whether your journey is really essential or whether you are able to avoid travelling during the worst conditions.
“If you must drive, do your preparations – check local weather and traffic reports, plan your route carefully using main roads where possible and consider alternative routes in case you encounter difficulties.”
In Yorkshire, the A61 was shut between Harrogate and Skipton due to the conditions, while further north, in Durham, the A66 was closed between the A1M and A685.
The A1 in Durham was also closed between Scotch Corner and Catterick after a lorry jackknifed.
Highways England said the A1 in Cambridgeshire had to be shut due to severe weather, between the A1M and A6121 at Tinwell.
A number of lorries jackknifed and vehicles were caught in queues for more than three hours.
In Norfolk, police also reported roads being blocked due to lorries and cars becoming stuck in the snow, including the A11 southbound at Wymondham and the A143 at Haddiscoe.
Rail passengers across Britain suffered from delays and cancellations on Wednesday, with almost all operators affected by the conditions.
The West Coast Main Line is closed between Carlisle and Scotland with no trains or replacement buses.
Alternative rail routes between England and Scotland are also severely disrupted.
All Caledonian Sleeper services between London and Scotland due to depart on Wednesday night were cancelled.
ScotRail urged commuters in the red warning area to head home as services will wind down on Wednesday afternoon.
Virgin Trains East Coast lifted its ticket restrictions for services on Wednesday, Thursday and Friday.
Dozens of Southeastern services were unable to run due to problems in several locations.
There were cancellations on the Medway Valley Line after train crew were unable to get to depots because of the heavy snow.
A snow clearing vehicle broke down and blocked the Ashford-bound line at Wye, while there was major disruption on metro routes between Dartford and London via Woolwich, Bexleyheath and Sidcup because of signalling faults caused by the weather.
Delays and cancellations on the c2c line from south Essex into London Fenchurch Street were worsened by freezing doors which prevented some passengers getting on and off trains.
Passengers were advised to check with operators before travelling.
There were cancellations of flights departing or arriving at Heathrow, with British Airways axing at least 103 services on mostly short haul routes.
London City Airport saw at least 98 flights cancelled. An additional six inbound flights were diverted or returned to their departure airports.
BA’s business class only service from New York to London City was forced to land at Gatwick, West Sussex, while the carrier’s flight from Frankfurt ended up touching down in Birmingham, 110 miles away.
All flights due to land at Leeds Bradford Airport before 4.30pm were either cancelled or diverted, and many departures were also unable to operate.
Shortly before noon Ryanair suspended all flights to and from Dublin Airport for the rest of Wednesday as a result of the snow which swept into Ireland overnight.
Glasgow Airport closed its runway from around 7am until 1pm.
Gatwick Airport said flights were arriving and departing, but some flights were disrupted.