A safety alert has been issued over a common type of parking brake in trucks that has failed, causing deaths.

Tens of thousands of trucks in New Zealand are fitted with the parking brake. Photo: 123RF

The Transport Agency put the alert out after four deaths in the last decade when a cardan shaft or transmission park brake failed on a vehicle.

Tens of thousands of small-and-medium trucks up to 23-tonne have this type of park brake.

"Avoid parking on slopes or use wheel chocks when parked on a slope and when the vehicle is jacked," the alert said.

The agency has been struggling for years over what to do about the brakes, as a mechanical fix is not straightforward.

It has been urging careful maintenance in the first place, because they are particularly susceptible to gearbox leaks.

"They are designed to hold the vehicle and its load but have limitations which can lead to a vehicle rolling away," the alert said.

Tests on 90 trucks near Wellington in 2020 found one in eight might roll away.

Rolling away risks are heightened if the truck's load is being changed or shifted, or the surface is unstable, such as on a building site.

The alert warns the routine six-monthly inspections of trucks "do not adequately assess parking brake performance".

"It is expected to be replaced by a more rigourous roller brake machine test from 1 October, 2022 for most classes of vehicle with cardan shaft brakes."

It was up to the vehicle owner to maintain the brake, the agency said, warning them to not assume that if they have a current Certificate of Fitness, this means the park brake is OK.

Worksafe put out a [https://www.worksafe.govt.nz/about-us/news-and-media/driveshaft-parking-brake-failures-in-commercial-and-industrial-vehicles/

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Documents show transport officials wanted to remove dodgy handbrakes from more than 1000 trucks by the middle of last year but it still hasn't happened.

The Transport Agency is continuing to work on what to do about truck handbrake failures that have caused deaths and injuries.

Tests on truck handbrakes have found high rates of failure, and concluded the way the brakes are routinely checked is ineffective.

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