Black ice and freezing fog predicted for Canterbury highways

Black ice, frost and freezing fog are predicted to make a gnarly mix on highways in Canterbury this week.

NZTA said forecasts could drop to below negative five degrees in places and bring frost mornings and icy roads.

Fog was forecast in the Mackenzie Basin, mainly south of Irishman Creek which NZTA said could persist all day on Wednesday and Thursday.

The risk of hoar frost and black ice was forecast to continue through to 12pm on Friday.

Further north, frost/ice could be expected to impact State Highways 1, 7, 73, 75 and 77 through the remainder of this week.

NZTA contractors would be out laying grit or anti-icing agents to help keep people safe on icy highways, an NZTA spokesperson said.

Drivers were urged to reduce their speeds, increase their following distances, and avoid sudden braking or turning movements on icy roads.

Ice was more likely to form in places such as bridges and shaded areas, and black ice could be harder to spot.

Staying as visible as possible, with headlights on in foggy conditions, also helped to keep people safe, NZTA said.