An in-service standard to manage engine brake noise has been approved unanimously by the Australian Transport Council (ATC)

The loud ‘bark’ caused by engine brakes on heavy vehicles fitted with worn, defective or inferior mufflers has been a community concern for some time, yet, until now, it has remained unregulated.

National Transport Commission (NTC) General Manager Safety & Environment Tim Eaton said the development of a national regulation and enforcement technology has been a collaborative effort involving government and industry.

“New South Wales put in the hard work in to pick-out the characteristic ‘bark’ of an engine brake from the traffic stream and measure it. South Australia led the development of ‘noise camera’ technology to enforce the noise regulation. Victoria has also been involved in trialing the technology,” he said.

“During consultation the community broadly supported the regulation, while the trucking industry’s views ensured it is practical and only targets the small number of operators who do the wrong thing.”

Mr Eaton said trucks fitted with purpose-designed mufflers in good condition are reasonably quiet and will not be impacted by the new regulation.

“Noise problems emerge when mufflers deteriorate or are replaced with inferior product, so fixing the problem is as easy as replacing the muffler,” he added.

“Once implemented by States and Territories, this regulation will help to ensure a minority of noisy vehicles do not result in community-led truck curfews and restrictions, which could impact on productivity.”

The Environment Protection & Heritage Council also voted unanimously in favour of the proposal.

A copy of the approved final Regulatory Impact Statement is available here: Engine Brake Noise: Final Proposal and Regulatory Impact Statement

What is an engine brake?

Engine brakes are devices fitted to the engine of heavy vehicles to help slow the vehicle down. They are often referred to as ‘auxiliary braking devices’ or ‘secondary retarders’. A driver switches on the engine brake and it engages on release of the acceleration pedal.

Operators use engine brakes to reduce wear and tear on the vehicle’s service brakes. Importantly, engine brakes improve vehicle safety by reducing the load on service brakes on a steep descent.

How does an engine brake work?

A change to the valve sequencing allows the engine to work as a compressor. As each piston reaches ‘top dead centre’ with valves closed, one valve opens; allowing compressed air to be vented at very high speed. This creates a ‘pulsing’ noise which, on a typical six cylinder truck engine operating around 1500 revolutions per minute, causes the characteristic ‘bark’ which the community finds annoying.

Noise regulation for new vehicles

ADR 83/00 regulates drive-by noise for new models manufactured after 2004 or any new vehicle from 2007/8. However, there is no regulation to specifically address in-service engine brake noise.

Engine brake noise recordings