A bus crash today that left a child seriously injured is a gruesome reminder of the dangers of black ice, the NZTA says.
The tour bus carrying 34 Chinese nationals rolled on State Highway 94, south of Queenstown, on its way to Doubtful Sound shortly before 9am.
A nine-year-old boy is in a serious condition in Dunedin Hospital suffering from internal injuries.
A 55-year-old man is also in Southland Hospital with chest and back pain, along with two women. One has a fractured ankle and the other has chest, shoulder and neck injuries.
New Zealand Transport Agency Southland area manager Peter Robinson said the crash should serve as a reminder for all motorists that extra caution is needed when driving in winter conditions.
"We're urging drivers to use extreme caution and be aware that conditions can change very quickly.
"Our thoughts are with those injured in the crash and their families," Robinson said.
The crash was among several that occurred in the same area this morning.
Mossburn chief fire officer Lance Hellewell said the conditions were "treacherous".
"It's been horrendous this morning, just continuous frosts over the last few days, and then a few showers of rain this morning, just made driving conditions rather treacherous."
China Travel Service tour guide William Peng said the bus he was in, which was heading to Doubtful Sound, was ahead of the bus that crashed when they heard it had slipped on ice and rolled.
"People (started) to climb out the roof. There was blood everywhere but not too serious," Peng said.
The driver turned back to help passengers on the crashed bus. They had not been trapped, and were put straight on a helicopter, Peng said.
Police are investigating the incident.