Many motorists asked why more grit was not spread, and many left their cars parked at the roadside.
Another heavy frost was predicted for this morning.
Yesterday, temperatures dropped to -5.2 degC at Dunedin International Airport and 1.2degC in the city.
Mr Standring said two grit trucks started work on Sunday evening and worked through the night to keep main roads gritted.
CMA, an anti-freezing agent, was also used.
Five other grit trucks, which started at 4.30am, were called away from their normal route to attend to callouts.
Shirley Beattie, of Mornington, avoided her usual route to work through the Glen and instead attempted to go down Eglinton Rd.
After watching other cars slide down the hill, she decided to pull over and wait.
She had been in her car since 7.15am when the Otago Daily Times spoke to her at 9.30am.
"It's not worth taking the risk," she said.
Another woman who had lived in Mornington for more than 20 years said she could always get to work if grit had been spread on the road.
"I don't understand why it hasn't been gritted," she said.
Mr Standring said there were a few areas of Dunedin that would not have been "served well".
However, the contractors did as well as they were able.
Senior Sergeant Steve Aitken, of Dunedin, said the crashes started on Sunday night when a motorist lost control of their car about 10.30am and crashed into Wakari Hair, on Helensburgh Rd.
The occupants received minor injuries, but the shop was significantly damaged.
It was boarded up yesterday.
Police were called to about three crashes in Dunedin city yesterday morning.
Most drivers were prepared for the slippery conditions, he said.
In the most serious crash, a man received minor head injuries after his four-wheel-drive vehicle slipped on ice and rolled down a steep bank on Dunedin's Northern Motorway about 6.30am.
Dunedin International Airport chief executive John McCall said ice at the airport yesterday morning was "as bad as I have seen it".
The first flight did not leave until 11.15am as airlines had to wait for ice on the runway to melt.
Labour tertiary education spokeswoman Maryan Street arrived in Dunedin hours late after she, along with dozens of others, had to take a bus from Invercargill airport.
PHOTOS: STEPHEN JAQUIERY
