Shocking driving from a tourist who overtook three cars and a bus on a blind corner near Tekapo led to a "citizen's arrest" on Christmas Day.

Timaru woman Amy Hollamby was horrified to watch the other driver pull out behind her across yellow lines and pass the line of traffic on SH8 about five minutes from Tekapo.

The line of cars all slowed down and pulled to the side as the other driver overtook, as there was no room for her to pull back in before the corner, but "she stayed on the wrong side of the road the whole way round".

"You couldn't see more than a metre ahead of you," Hollamby said.

All she could think was that they were about to witness a head-on crash, but luckily for the driver and the others on the road, there were no oncoming vehicles around the corner.

"If there was, they were mincemeat."

The scariest part was that any oncoming driver would have been doing "absolutely nothing wrong" but could well have been killed by the woman, who Hollamby said was travelling at speeds above 100km/h.

"I was so angry," she said. "I said 'if she pulls in in Tekapo I'm pulling in too.'"

The driver did pull in upon reaching Tekapo, and Hollamby along with the two other overtaken cars pulled over and boxed the vehicle in so she could not drive away.

Another driver was yelling and swearing at the woman, but Hollamby said she tried to take a kinder approach and point out to the woman that in New Zealand cars stick to the left. She pointed to a sticker on the woman's rental vehicle that said to keep left.

She said the woman told her "I was on the left, I tried very hard to stay on the left".

Hollamby told her it was "the worst driving I've witnessed".

The woman, who told Hollamby's husband she was from China and had arrived in the country on Christmas Eve, appeared oblivious to what the issue was. She had driven down from Christchurch.

"She still to this day probably has no idea what she did wrong."

Some of the other travellers went to the nearby police station and brought an officer over, who took the keys from the ignition and pocketed them.

Hollamby, who had her whole family in the car with her, said she didn't feel she was at risk of being involved in a crash, but was certain they were about to witness someone die on the road.

She travelled the route often and said she had witnessed poor driving from tourists in the past. Her husband had also been involved in an incident where he had confiscated another driver's keys.

Hollamby encouraged other drivers to take action if they believed someone's driving was dangerous enough. In rural areas it might take some time for police to arrive, and it might not be fast enough to prevent a death, she said.

"Something needs to be done on a higher level."

Police have been asked for comment.