Freezing rain causes more than 100 crashes in Cumbria
Emergency services in Cumbria dealt with more than 100 road traffic incidents earlier, all caused by freezing rain.
The A66 trans-Pennine route was closed for several hours after a number of lorries jackknifed near Stainmore.
The M6 and the A66 near Penrith also saw a number of crashes. There were no serious injuries reported.
The Met Office say there will be further risk of ice overnight, with temperatures again dropping below zero.
Police have urged drivers not to take to the roads unless journeys are "absolutely necessary".
Some schools were also closed as a precaution.
A Cumbria Police spokesman said all the collisions were reported between 05:00 GMT and 11:00 GMT.
He said: "All of the county's roads have been affected by ice and we are warning people to take care.
"If your journey is not essential, then please do not drive. If you do have to travel, please take extreme care when driving, slow down and keep a substantial braking distance from the car in front."
Health officials said accident and emergency staff at the Cumberland Infirmary in Carlisle were working hard to deal with numerous victims of road accidents who had suffered non life-threatening injuries.
Derek Cartwright, director of emergency services for the North West Ambulance Service, said: "We have already experienced a higher number of road traffic collisions than normal in Cumbria and we are urging the public to take extra care whilst out on the roads.
"We need older people and those who have long-term conditions to make sure they keep taking their medication and have sufficient supplies so that they don't need to go out for more during the cold spell.
"I would urge people to be good neighbours and make sure the people they live near, especially ones who are older or suffering from serious illness, are safe and well this winter."
A spokesman for Cumbria County Council described road conditions as "challenging" and said extra gritting shifts had been ordered.
He said: "This has turned into a sort of perfect storm of bad weather.
"We have got very low ground temperatures with rain falling on top of that as a band of warm air has come in.
"This has lulled people into a false sense of security because the ground looks wet when in fact it is frozen.
"Our gritting crews did a full run last night and are running at full capacity today to do what we can to counter the hazardous conditions.
"We are expecting these conditions to last for about the next 24 hours."
Parish councils were offered additional supplies of grit in an effort to keep rural access routes open.
Some bus services were also affected, including the Fellrunner service from Langwathby to Penrith, which was cancelled.
Find your local BBC site
Elsewhere in the north of England, six vehicles, including a double-decker bus, crashed on the Felling bypass and several vehicles collided on Blaydon Highway flyover, both in Gateshead.
Durham Police said they had received reports of a number of minor collisions around County Durham and Darlington. They warned drivers to use "extreme caution".
Plunging temperatures and icy conditions also led to a number of road accidents across North Yorkshire. Police said black ice led to problems in Skipton, Otley and Settle and one motorist said the A65 near Giggleswick was "like glass".
BBC weatherman Paul Mooney said rain falling on to frozen roads had created sheet ice and led to hazardous roads and pavements.
He said: "When that rain and drizzle hits those freezing roads and pavements it just freezes instantly and creates sheet ice.
"It might just look like a damp road or pavement but it's really ice and very, very dangerous."