Research is carrying on to ensure any changes to testing standards of a problematic truck handbrake make things safer.
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The cardan shaft handbrakes that are common in many types of Japanese trucks, and among construction machinery, have a record of failing, causing accidents and two deaths in recent years.
The weakness in the brakes is often missed in the limited tests done by vehicle testing stations.
The Transport Agency said it was following up on truck testing last year with more research to make sure any changes to testing standards make things safer.
Any changes must be manageable for operators, and be backed by technology, it said.
RNZ has asked Waka Kotahi to release the results of the truck testing.
"The project brought together technical experts, representatives of vehicle testing agents, commercial transport representatives, and experts in statistical analysis to ensure the output would identify and break down issues for both immediate and ongoing action," it said.
The agency first put out safety alerts in 2013, and there have been repeated warnings in the years since that many drivers do not know the risks of the brake failing quickly if it is not properly maintained.
In a 2018 accident that killed a mini-crane operator, the brake failed after two minutes. Two workers standing nearby yelled a warning, but only one of the two men, who were trying to put a tow line onto a truck, was able to leap out of the way.
That accident was on a Ryman Healthcare site, and the company is now funding a $150,000 education campaign about the risks.
It was a "complex technical" problem, NZTA said.
Last month in a letter to 1000 truck owners, the agency responded to another truck handbrake danger by ordering the replacement of all Sanwa Seiki brake valves.
"Vehicle owners, drivers and those that maintain the vehicles have a responsibility to ensure vehicles are in a safe working order at all times and are required to have practices in place to identify and address safety risks," it said.
