The couple who called *555 to alert police to the driver say at one point, he stopped on a Cobham Dr roundabout, blocking traffic.

When police caught up with a drunk driver in Hamilton late on Sunday, they had to call a doctor in to assess him. The 45-year-old was so drunk, police couldn't breath-test him.

The pair who reported and then followed him until police could get there saved lives.

Had it not been for the couple, who called *555 after being cut off at the Cobham Dr bridge, it might have ended in tragedy, Waikato police Senior Sergeant Stephen Ambler said.

"They undoubtedly saved lives," said Ambler.

The Hamilton man and his partner were heading home about 11pm when they were cut off by a silver Mitsubishi Diamante.

"We turned right to go towards the bridge - it's two lanes and they cut in front of us. They were driving really, really fast, so we slowed right down to keep our safety space," said the driver, who did not wish to be named.

Approaching Hamilton Gardens, the witness said the driver was "all over the road", swerving on to the opposite side at high speeds.

"They stopped halfway on the roundabout to give way, but there was no point, because they were blocking it."

"It was really stupid - I knew I had family members on the roads at that time, so we called *555 to tell the cops about it."

Police asked if the driver could follow the vehicle until they arrived.

"We were just going home, so thought, yeah, we can do that."

But they were not prepared for what they would see.

"They started driving up on the footpath, did two illegal U-turns, came close to going up on the median. I was scared for our lives and also all of the others out there."

As the couple followed the sedan through Hamilton, oncoming cars were forced to swerve as the Mitsubishi drifted across the centre line, he said.

"It was reckless, stupid drunk."

About 10 minutes after he called police, two patrol cars arrived on scene and stopped the Mitsubishi on Cambridge Rd near Riverlea Car Wreckers.

"We overtook them and stopped because we were shaken up, hearts racing," the driver said.

"I think he would have killed somebody - if not himself, there would have been a head-on collision."

Ambler said the man was arrested and charged with driving while incapable.

"He was in such a state he was unable to provide a breath test and a doctor had to assess his level of impairment," Ambler said.

It was understood to be the man's first drink-driving offence and he would be summonsed to appear in Hamilton District Court at a later date.

The arrest came at the end of a weekend of shocking drink-drive results in Hamilton's CBD. Seventeen drivers were found over the legal 250 mcg limit.

"It is an incredibly high result and police are disappointed," Ambler said.

Traffic is already increasing in the Waikato in the lead-up to Christmas and drivers need to be cautious and alert, he said.

Any dangerous driving can be reported to police by dialling 111 or *555.