Black ice has been reported in “many areas” of Devon and Cornwall, police have said.
Two yellow weather warnings for ice have been issued by the Met Office for parts of the counties.
The Met Office first issued a warning at 06:30 GMT to 10:00 on Friday and has issues a second between 18:00 on Friday and 10:00 on Saturday.
A yellow weather warning for snow and ice has also been issued by the Met Office between 15:00 on Sunday and 12:00 Monday.
Police said on social media on Friday: “If you are travelling on the roads, please drive to the conditions and with care.”
The Met Office warned of ice on untreated paths and pavements.
On Wednesday, the UK Health Security Agency (UKHSA) issued an amber cold health alert for the South West until 6 January at 10:00.
The Met Office said showers had “fallen on cold surfaces leading to the development icy patches, especially on untreated surfaces”.
