The re-testing of bus and truck brakes on Waiheke Island has not found any that are sub-standard, according to vehicle inspection company VTNZ.
VTNZ said 18 customers took up the offer of free re-tests.
VTNZ and Transport Agency offered the re-tests after the company admitted using an older, less effective brake test method on the island for 18 months, instead of the two days the rules allow.
"Of the 18 customers who took the opportunity to retest vehicles to date, every single one was up to the required standard when tested on the roller-brake machine newly installed at Waiheke," the company's country manager Greg O'Connor said in a statement to RNZ.
The Transport Agency knew VTNZ was using the old decelerometer method of testing as a "temporary arrangement", he said.
"I want to reiterate both NZTA and VTNZ believe safety was not compromised during the time that the roller-brake machine was unavailable."
A former VTNZ manager kept records he said showed a big drop-off in detecting brake problems under the old method.
The Transport Agency is being now being investigated by the Transport Ministry over its failure to enforce road safety rules.
"This is a systemic failure across one of our most important government agencies" that had been going on for a decade, the Transport Minister Phil Twyford told RNZ today.