Resident Abby Crook said the Bayes Coachlines bus had been carrying Orewa College students and had just dropped off the last group, including her teenage daughter, when it slid down the hill.
"It teetered on the edge of a cliff held only by a transformer pole."
Traffic was backed up, with motorists unable to get into Gulf Harbour until the road reopened about 9pm, when a truck was brought in to haul the bus away. Power was cut to surrounding houses and residents reported queues of traffic as late as 10pm.
Mrs Crook said she and other residents had to park on the street and walk to their homes.
"There's a stairwell that goes down ... and none of us could get to that stairwell to get home. And the only thing holding it was the transformer pole - that's what the fireman said. None of us could go past there in case the power lines were live."
A St John spokeswoman said no one needed medical treatment.
A Bayes spokesman said wet conditions contributed to the crash and the company would investigate.
"We're not sure what's happened ... but there were no passengers on board. The driver's fine. He wasn't injured at all ... and the bus is back at the depot."
In the other incidents:
A crash involving five cars occurred in the southbound lane of the Northern Motorway near Esmonde Rd.
An elderly man was taken to hospital with head and leg injuries after his car veered off Atkinson Rd in Titirangi and rolled down a bank about 4.30pm.
A young woman suffered moderate injuries after the car she was driving hit a power pole in Te Atatu South about 5.51pm.
Senior Sergeant James Hall of Waitemata Police said: "This has been a busy afternoon for police. Today's rain has led to traffic congestion and a change in roading conditions, and we ask anyone who gets behind the wheel of a car to keep that in mind, especially if they're heading away for the holiday weekend."
