At least three vehicles, including a concrete truck, were involved in a pile-up in the south-bound lanes of State Highway 1 near Green Island, which closed the motorway for almost an hour from 12.30pm.
Contractors working on the road had closed one lane, and signalled for motorists to merge into the other lane near the start of the motorway and the permanent 100kmh sign.
A temporary 50kmh sign was also set up, but it appeared some motorists failed to notice the signs. Senior Constable Helen Fincham-Putter said at least three, and probably four, vehicles collided where one lane closed.
It appeared some motorists had missed the merging sign and when forced into one lane by cones, collided with other motorists.
The most severe collision was between a concrete truck and a Toyota Land Cruiser, she said.
Five family members in the Land Cruiser were taken to Dunedin Hospital for assessment, although Snr Const Fincham-Putter said no-one was seriously injured in the collision.
The entire highway was closed because debris from the damaged vehicles had littered all four lanes.
The second accident on the motorway occurred at 4.45pm, between the Saddle Hill on-ramp and the Quarry Rd off-ramp.
A 51-year-old motorcyclist came off the Suzuki road bike he was taking for a test ride, when up to a dozen cars suddenly braked to avoid a car, which had swerved away from the central crash barrier.
''A lady driver got too close to the wall and swerved out. It made everybody just lock on the brakes. He did the best he could to get out of the way, but he had nowhere to go,'' witness Craig Clapperton said.
Traffic was backed up to Lookout Point for more than an hour while the motorcyclist was treated and the scene cleared.
He was transferred to Dunedin Hospital with shoulder and leg injuries and lacerations.
Two other patients were also taken to hospital; one with a fractured wrist and the other with seat-belt contusions.
Snr Const Fincham-Putter asked anyone who witnessed either incident to contact her on 021-191-5082.
