Eighteen trucking companies are being investigated after a police crackdown uncovered mass safety breaches on the highway north of Auckland late last year.
Truckers say cowboy operators have been flouting safety rules under the nose of police for years.
Officers checking on hundreds of trucks clearing containers from Whangarei port last December found almost one in five were unroadworthy and posed a serious risk to the public.
Now the Waka Kotahi - the NZ Transport Agency is looking into 18 companies which had multiple faults detected in their vehicles.
It's looking especially at what their systems for maintenance and managing driver fatigue are like.
Waka Kotahi refuses to name the truckers, saying only that they are based from the Central North Island through to Northland.
Lance Peach who runs Auckland firm Superfreight made the Northland run several times - he slams the police's commercial vehicle safety team.
