The Transport Agency is continuing to work on what to do about truck handbrake failures that have caused deaths and injuries.
Photo: 123RF
Tests on Cardan shaft handbrakes that are in tens of thousands of commercial vehicles found high rates of failure.
Trucks manufactured in Asia and weighing up to 23 tonnes typically have this type of brake.
Waka Kotahi said several factors could have contributed to the poor condition of handbrakes found in about half the trucks.
"We are continuing to work on the next steps outlined in the recommendations to address the issues found in this sample of the New Zealand light truck fleet," it said in a statement.
Tests on 90 trucks near Wellington last September found one in eight might roll away.
The testing reported 30 percent of drivers had experienced a handbrake failure, including runaway trucks.
The agency refused to provide details about a fatality in March last year linked to the brakes which prompted the tests. RNZ has asked for details from Worksafe.
There were earlier fatalities in 2017 and 2018.
The March fatality "is still under investigation across various agencies but our investigations indicate the vehicle had a Cardan shaft park brake", NZTA said.
A safety system trialled last year was in the development phase only for Cardan shaft brakes, it said, and it had followed the progress of this system.
NZTA listed factors that could lead to handbrakes being in poor condition:
- Stretched park brake cable
- Excessive application force required to operate the lever
- Contamination of the brake linings (oil)
- Excessive free play in the linkages
- Worn-out or mis-adjusted brake shoes
- Excessive lever travel and
- "Other factors which could affect the holding power of the brakes"
An industry insider said the agency should encourage operators to fit hydraulic locks to the handbrakes. This would be an effective temporary fix that might cost about $1500 per truck, they said.
NZTA and Worksafe say Cardan shaft brakes need careful maintenance and adjustment.
The risks include oil leaking from the engine or transmission onto the handbrake. Engaging the handbrake while the vehicle is still moving is likely tp wreck it so it cannot be used for emergency braking.
Waka Kotahi deputy general manager of regulatory services Neil Cook said the agency was "investigating improvements to the testing method at the time of CoF, including testing the brake in both directions".
The testing provided "valuable insight" into the operation of brakes, drivers' knowledge of them, and "the capability of these brakes when tested to the Heavy Vehicle Brake Rule".
"This evidence is informing our next steps, which include an education campaign about how to mitigate the risks associated with these brakes and the need for regular maintenance."
It was also looking into how to improve routine handbrake testing by clarifying protocols for the stall test done during Certificate of Fitness checks, Cook said.
It might bring in a maintenance form, called a 4085D, of a type trialled last year.
If a vehicle inspector is not satisfied with brakes during the stall test, the form requires the owner to get the brake serviced before a COF will be issued.
