More snow is forecast overnight in Devon
More snow is expected to fall overnight with an amber snow warning for mid, north and east Devon.
The Met Office has issued a yellow warning for snow and ice for the whole county.
Devon County Council said all 37 of its gritters would be out during the evening.
Ice and hail caused a number of accidents on Tuesday, with one man in a critical condition after a collision on the A38 near Manadon.
Devon and Cornwall Police said several vehicles spun off the Exeter-bound carriageway of the A38 between Manadon and Marsh Mills near Plymouth.
The first accident happened just before 06:00 GMT and the road was shut until about 16:00.
Police said freezing road conditions may have been a contributory factor.Gold command
Snow, ice, rain and sleet affected many parts of the county during Tuesday, with 2-5cm (1-2in) of snow expected overnight and up to 5-10cm (2-4in) on high ground.
Devon County Council said ice was still causing a problem, despite gritters treating roads.
It urged commuters and other road users to take care on Tuesday evening.
Drivers should check weather forecasts and road conditions before they set out, it said.
Police said they were expecting snow to settle on Haldon Hill, near Exeter, on Tuesday night.
Officers added that an action plan was in place to keep the A38 trunk road in the area open.
Ch Insp Ian Drummond-Smith of Devon and Cornwall Police said on Twitter a gold command had been set up, involving "scores of other agencies", to deal with weather-related problems across the force area.
Several school bus routes were cancelled due to ice on the roads.
Plymouth City Bus tweeted that Eggbuckland, Efford, Deer Park, Holly Park and Austin Crescent in the city were "out of bounds" for buses because of the ice.
Heavy rain has also caused surface flooding in parts of Devon, including the A396 between Bickleigh and Rewe.
Fast-flowing flood water at Copplestone led to the temporary suspension of trains on the Tarka Line, with buses replacing trains between Crediton and Barnstaple.
The Environment Agency has issued a flood warning for the River Clyst, saying it had "responded to today's rainfall and snow melt", and with rain forecast throughout the day it could rise further.
There is also a flood alert for the River Culm due to the rain and melting snow.