KEY POINTS:
Roana McCrossan's maternal instincts took over when she saw a young child in the back of a car that was swerving dangerously on a Southern Alps road.
A truck driver had also become alarmed by the vehicle and he and another motorist used their vehicles to box the car in, forcing it to slow down and stop.
Ms McCrossan asked the female driver to hand over her 7-year-old daughter, offering her a lift in her car. The woman agreed.
Ms McCrossan's worst fears were realised two kilometres further on when the vehicle slammed into a boat trailer being towed by a 4WD vehicle.
The occupants of both vehicles escaped without injury.
"I just said [to the driver]: 'Do you want me to take your daughter?' " said Ms McCrossan.
"I thought, 'Oh my God, is she going to nut out or what?' I didn't know if she was on P or what she was on. And she just said, 'Yep, that's fine'. The mother gave me the wee girl's bag and everything.
"At first, I was shaking but then I thought: 'Thank God I got that kid'."
Police have praised Ms McCrossan for her actions, but have warned that it may not be the safest course of action in all situations. The driver, who is on a drug rehabilitation programme, has since been charged with careless driving offences.
Ms McCrossan, of Southbridge, about 40km southwest of Christchurch, was travelling home with her two daughters, Courtney, 10, and Mikyela, 6, from the West Coast when she came across the swerving car at the mountain crossing area of Otira.
At one point, the woman driver picked up hitch-hikers, one of whom drove for a short time.
Ms McCrossan's heart sank when she spotted the girl. "I thought, 'Oh my God, there's a kid in the car. What am I going to do?"'
The girl was scared to go with a stranger at first but was eventually convinced to go with Ms McCrossan. The girl told Ms McCrossan's children: "I had to keep waking mummy up, because she was going to sleep".
Senior Sergeant Stewart Munro said a police car had been on the way from Canterbury to intercept the woman, but her vehicle crashed before the officers arrived.
He said Ms McCrossan deserved to be congratulated for her actions but people should be cautious approaching people in that type of situation, which could be fraught with risk.
"Her driving was so bad on that road that we don't believe she should have a driver's licence at the moment," Mr Munro said.
"We're going to take steps to get her licence removed."
The girl has since been reunited with her mother and police have no plans to involve Child, Youth and Family.
