Traffic on State Highway One south of Christchurch is being redirected through a long back-road detour because of a fatal crash.
The accident happened between Rakaia - Chertsey, closing the highway.
A 10km detour takes travellers along Thompson's Track.
Police say icy road conditions may have been a factor and are warning motorists to take care.
Conditions are so bad, emergency service staff are reportedly having difficulty walking around the crash site without slipping.
An Australian man died near Greymouth when the car he was in, slid on ice and went off the road on Monday morning.