Three thousand truck and heavy vehicle certifications have been revoked this year, compared to just five in total two years ago.

The surge began last year when 2000 were revoked and is mostly pegged to the belated detection of poor work by two certifying engineers in Nelson and Auckland, Peter Wastney and Patrick Chu, according to the New Zealand Transport Agency (NZTA).

It expected numbers to drop "dramatically" once it finished investigations that had gone on for two years and as it carried on with more rigourous monitoring, NZTA said.

Numbers of heavy vehicle certifications revoked

•   1 Dec 2018 to present: 3186

•   1 Dec 2017 to 31 Nov 2018: 2103

•   1 Dec 2016 to 31 Nov 2017: 5

Other new figures show 67 heavy vehicle owners have had low safety risks identified in towing connections since last December, and been told to get them checked.

Sixteen thousand owners were contacted about a product recall over airbag risks.

Ten light vehicle owners had risks around repairs detected, and half of these certifications were revoked.

And 71,000 vehicle owners were alerted to potential safety risks related to a warrant of fitness issued by a suspended garage.

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Sixteen thousand owners were contacted about a product recall over airbag risks.

The agency also elaborated on its investigation of chassis problems with trucks that followed on from the towing connection investigations, saying it told its licensed certifiers to submit files under its earlier regulatory compliance review that ended in mid-2019.

"These files formed the basis of the desktop review that is ongoing, and the basis for certain vehicle inspections, which are ongoing".

Also, minimum standards for such files were introduced this year, and it was reviewing files to check on that.