Waikato police are praising the actions of motorists who dobbed in a truck driver seen swerving all over a state highway.

Senior sergeant Pete van de Wetering says the truck and trailer unit was seen driving dangerously on State Highway 29 near Matamata about midnight.

"It was driving in a form that was dangerous, where the truck was spending too much time across the centre line. So it was quite a potentially dangerous and risky situation."

The driver of the car -- which was travelling in front of the truck -- called police and at the same time tried to slow the truck down by slowing his car down too, but that didn't work, Mr van de Wetering says.

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"The people in the car tried first of all with their warning lights to try and slow the truck driver down and he didn't respond to that, he literally overtook them, so the people in the car couldn't do more than that."

Another truck driver also noticed the manner of the truck's driving and alerted authorities, too.

The truck finally came to a halt after being pulled over by police responding from Matamata.

Mr van de Wetering wouldn't elaborate on what the offending truck driver told police in his explanation for his actions, but says his response would be taken into account during their investigation.

The driver had been subsequently stood down from driving for a period of time, he says.

"The point that I make here is that we are impressed and thankful that members of the public really made efforts to alert us in the first instance ... road safety is everyone's responsibility. In this case here, it was a successful response by members of the public -- they didn't ignore what was a potentially dangerous situation."