The male driver and sole occupant of the school bus was trapped for about an hour before being extricated by firefighters.
He was taken to Christchurch Hospital by the Westpac Rescue Helicopter with moderate injuries, and have since been discharged.
Today, police said they were working with Ms Armstrong's family, and victim support had been offered to them.
"Charlotte's family have lost someone very special to them in tragic circumstances," Mr Piper said.
Mr Piper said black ice was a hazard on many Canterbury roads yesterday.
He said the police investigation into the cause of the crash would include assessing the effect of a large patch of black ice that was in the area where Ms Armstrong crashed.
Canterbury police have also released the names of those involved in a fatal crash near West Melton yesterday afternoon.
They were 88-year-old Patrick Eugene Joseph Barry and his wife 81-year-old Betty Dora Barry from Christchurch.
Their deaths have been referred to the coroner.
Mr Piper said the couple were travelling north along Sandy Knolls Rd toward a stop-controlled intersection with Halkett Rd when the accident occurred just after 2.30pm.
"Their car has collided with a Toyota Hilux towing an empty horse float travelling west along Halkett Road."
Investigations into the cause of the crash were continuing.
