Police monitoring trucks on the road between Northport and Auckland have found almost one in five were unroadworthy and posed a serious risk to the public.
The police checks coincided with an abnormally large number of trucks moving freight between the two destinations after a large container ship bound for Auckland had to dock at Whangārei.
Trucks were expected to make about 800 additional trips over a week between the two destinations, carrying about 1200 containers.
Police inspected 534 vehicles, and 96 of them failed the inspections.
Eleven trucks had faults so serious they had to be taken off the road.
The single-biggest problem was lighting faults, but there were a high number of failures relating to tyres and brakes.
Senior Sergeant Mike Flatt, team leader for the commercial vehicle safety team, said in a statement that police were warning trucking companies and drivers of the importance of checking their trucks are up to a roadworthy standard.
"Trucking companies have a duty of responsibility to all motorists to ensure their vehicles are safe and not putting their drivers and other members of the public at risk," he said.
"Truck drivers also have a responsibility themselves to ensure whatever truck they are given to drive is up to COF standards and they should always be doing a "pre-drive" check of the vehicle - particularly focusing on brake systems, tyres and lights etc."
The police issued 81 infringement notices and 21 written warnings.