Muffler businesses should boom in the wake of a clampdown on engine brake noise.
National Transport Commission safety spokesperson Tim Eaton said engine braking noise on heavy vehicles fitted with worn, defective or inferior mufflers had been a community concern for some time.
“During consultation, the community broadly supported the regulation, while the trucking industry's views ensured that it is practical and targets only the small number of operators who do the wrong thing,” he said.
Engine brakes are engaged on the release of the accelerator to help slow the vehicle down and are used to reduce wear and tear on the vehicle's brakes.
Drivers believe that engine brakes also improve vehicle safety by reducing the load on brakes during a steep descent.
Eaton said trucks fitted with purpose-designed mufflers in good condition were reasonably quiet in any case, and would not be impacted by the new regulation.
“Noise problems emerge when mufflers deteriorate or are replaced with an inferior product, so fixing the problem is as easy as replacing the muffler,” he added.
“Once it has been 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 development of a national regulation and enforcement technology involved government and industry and was unanimously supported by the Environment Protection and Heritage Council.
Eaton said New South Wales identified the characteristic 'bark' of an engine brake from other surrounding traffic noises and measured it, while South Australia has developed 'noise camera' technology that could be used to enforce noise regulations and Victoria helped to trial it.
The Regulatory Impact Statement can be seen at the NTC website
How does Truck engine braking work?
A change to the sequencing of the valves allows the engine to work as a compressor.
As each piston reaches 'top dead centre' with the valves closed, one valve opens, allowing the compressed air to be vented at very high speed.
This creates a 'pulsing' noise which, on a typical six-cylinder truck engine operating at about 1500 revolutions per minute, causes the characteristic 'bark,' which the community finds annoying.
