A 12-year-old girl and her 14-year-old sister are facing a long grounding after the younger sibling went on a joyride in her parents' car and crashed head-on with her sister - who was looking for her in another vehicle.

The two girls were yesterday at their Te Kowhai home on the outskirts of Hamilton after they were discharged from Waikato Hospital on Tuesday - one with minor internal injuries, the other with a broken wrist.

Their mother said the two girls had made a "colossal mistake" and while she was extremely grateful both were alive, she said they were likely to be grounded for some time.

"It's not the best way to start the new year," she said. "It has all been very stressful for us.


"They have still got a future ahead of them. I just don't think we can determine what will happen from one incident ... They have made a really bad choice."

Both the woman and her husband were at work at the time of the accident.

District road policing manager Inspector Marcus Lynam said police were alerted by a woman before the crash in Te Kowhai Rd, which is in a semi-rural area and is a 100km/h zone, about midday on Monday.

"A member of the public had phoned 111 concerned about the driver of a blue Ford Falcon who had nearly hit her and said the driver couldn't see over the steering wheel," he said. "Then, a short time later this vehicle collided head-on with a Nissan Bluebird coming out of a driveway.

"We are very fortunate that no one was seriously injured but the poor member of the public who had already rung 111 concerned about the 12-year-old's driving was understandably distraught when she saw what happened."

Both cars were extensively damaged and were yesterday covered with tarpaulins at the end of the family's driveway.

Mr Lynam said that with Waikato's 2012 road toll of 45 being the highest in the country, police could not take such matters lightly.

He said it was too early to say what charges the girls might face, if any.