Police are advising drivers to slow down after a spate of accidents caused by the icy conditions.
A spokesman said that they have been inundated with calls about traffic accidents.
Police are asking drivers not to make any non-essential journeys.
The main trunk road through Cornwall remains closed this morning because of sheet ice.
The closure of the Bodmin to Okehampton stretch of the A30 was due to a high number of accidents.
A police spokesman said: "Highway officials are busy trying to grit and rectify the situation but the entire stretch of road will be closed in both directions until further notice."
Police are advising motorists to avoid the route.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here