The trucking industry is welcoming an investigation into heavy vehicle certifiers, saying it should never have got to this point.
Certifiers are accredited by New Zealand Transport Agency (NZTA) and are tasked with carrying out inspections on heavy vehicles.
Two certifiers have recently been suspended by NZTA after a series of near-misses led to the discovery they were approving unsafe trailer connections and in April it revoked more than 800 certifications and required them to be re-checked after 61 faulty towbars were found.
It is now looking into some other certifiers and allegations that they were signing off on towing connections by looking at photos instead of checking them in-person.
Road Transport Forum chief executive Ken Shirley said NZTA had been under-resourced for years, meaning certifiers had little government oversight.
"We've been concerned that NZTA as the regulator didn't really seem to have the capacity and the competence and the skill sets or more particular, the personnel, to adequately oversee its regulatory functions."
NZTA cut its heavy vehicle compliance team of a dozen in half in 2014.
Mr Shirley said the repercussions of this was something they had raised with the NZTA multiple times.
"They have to accredit the certifiers, they need to monitor and audit them."
RNZ contacted four major trucking companies.
Mainfreight said its drivers were owner-operators and therefore responsible for making sure their certifications were up to scratch.
It did not know how many of its trucks had been re-checked and said that was not something the company got involved with.
Halls said 12 out of 150 trucks needed their towing connections repaired or replaced.
Neither PBT nor Freightways returned calls.
The truckers union said some of its members are worried the trucks they were driving could be dangerous.
First Union secretary Jared Abbott said it was a serious safety issue.
"A lot of our truck drivers are actually working in rural areas, in forest areas and the roads there just aren't up to the same standard.
"It really puts drivers at risk, but it also puts the public at risk."
Mr Abbott said while it was great NZTA would be beefing up its oversight of certifiers, he was sceptical about whether it would make a difference.
"No amount of [staff] numbers is going to change that if they're still going to allow companies to get away with cutting corners."
NZTA Customer Design and Delivery general manager Charles Ronaldson said it followed up on any specific complaint or concern raised and was committed to ensuring a high standard of heavy vehicle certifications.
"We rely on the support of a network of qualified professionals to carry out the services which they are appointed to provide to a high standard.
"It is extremely disappointing when a person appointed to carry out these specialised services fails to perform their duties."
NZTA would suspend other certifiers if it was necessary. It was recruiting three additional auditors (trained engineers) and two additional heavy vehicle engineers."