Hundreds of schools and children's nurseries have been shut across the Bradford district today after several inches of snow fell overnight.
Although most main roads, including motorways, are passable with care, drivers have been warned that conditions on others are extremely treacherous.
A Highways Agency spokesman said: "Although we've treated the roads consistently throughout the night the roads could still have patches of ice, so those people who do have to drive, we're asking them to keep their speed down, keep the distance between themselves and the car in front to avoid any sharp braking.
"Some of the local roads will still be very difficult".
David Williams, Yorkshire Ambulance Service deputy director of operations, said: “Our staff are working extremely hard to get to people who call upon us for help as quickly and as safely as possible but understandably hazardous driving conditions may lead to extended drive-times meaning it might take us a little longer than normal to reach patients in the worst-hit areas.
“Please take extra care when out driving or walking and where possible avoid travelling at all in icy or snowy conditions. If you do have to go out, ensure that you wear appropriate footwear and warm clothing.”
The hazardous conditions have also led to many bus services being suspended, or altered to stick to main routes in Bradford.
• 268 suspended
• 425/427 suspended
• 607, 617 & 618 using Broadstone Way only in Holme Wood
• 610 main roads only - not serving Bartle Lane or Hollingwood.
• 613/4 using Otley Road and Killinghall Road
• 615 not serving Allerton (missing Bell Dean Road/Saffron Drive)
• 617& 618 not serving Bell Dean Road & Saffron Drive, terminating at Stoney Lane
• 620 running direct on Toller lane (Haworth Road side), operating on Bierley Lane in both directions.
• 622 & 623 not serving Chemical Works.
• 626 not serving Knoll Estate.
• 633 & 634 main roads only
• 645 not serving Ravnscliffe - using Harrogate Road and New Line
• 675 & 677 main roads only, not serving Ashbournes, terminating at Cottingley roundabout.
• 680 using Oak Lane in both directions.
• 846 & 847 main roads, use Kings Road direct.
There are also 30 minute delays on rail services between Bradford Forster Square and Ilkley/Leeds and Skipton and Leeds.
One lane of the M62 westbound between junction 25 at Brighouse and junction 22 Rishworth Moor is blocked because of snow.
Leeds-Bradford Airport is open, but is advising passengers check with their airlines for any disruptions before travelling.