Noise camera a ‘sound’ initiative


The NZ Transport Agency is working with the Road Transport Association NZ, Log Transport Safety Council, and National Road Carriers to reduce engine braking noise through a trial in Tauranga.

A ‘noise camera’, which has been installed on SH2 Takitimu Drive near the Elizabeth St roundabout, is at the centre of the trial.

Transport Agency Freight Director Harry Wilson says the camera, a first for New Zealand, photographs only those trucks using noisy engine brakes.

“We chose Takitimu Drive because there have been numerous complaints from local residents over the years, and the issue has persisted despite the Transport Agency putting up signs asking drivers to not use engine brakes,” Mr Wilson says.

Mr Wilson says road transport has an important role to play in the local economy, especially through transporting goods to and from the Port of Tauranga.

“Goods need to be transported by road, especially in a city like Tauranga where good access to the port is critical to both the local and national economy. The Transport Agency is focussed on ensuring road freight is moved as safely and efficiently as possible and this includes engine braking noise which needs to be appropriately managed to avoid disturbance to residents,” Mr Wilson says.

National Road Carriers spokesperson Grant Turner says that engine brakes are important in the safe operation of a truck especially when fully laden and out on the open highway, however they are unlikely to be needed in locations such as Takitimu Drive.

“Engine braking in built up areas with a speed limit of 80km/h or less is unnecessary, it upsets local residents and destroys community goodwill,” Mr Turner says.

Log Transport Safety Council spokesperson Bruce Nairn says the noise camera is a positive step towards identifying and reducing the noise impacts on the neighbouring residents.

“The camera combines visual images, audio readings and time and location information to provide a complete ‘real time’ overview of engine braking on the highway,” Mr Nairn says.

Road Transport Association Bay of Plenty Area Executive Charlene Kerr says that only a small number of existing vehicles – around 1% of the entire New Zealand truck fleet – have noisy engine braking systems.

“While only a minority of trucks and drivers cause engine braking noise, it takes only a small number to cause disturbance, especially at night. It’s only a few drivers that give the entire heavy vehicle industry a bad name” Mrs Kerr says.

Mr Wilson says the Transport Agency and industry associations are working together to achieve compliance with truck drivers that are identified by the camera as using noisy engine brakes and will call in local Police only as a last resort.

“We’re trialling the camera and compliance process to see what works before deciding whether to move the camera to other areas where engine braking noise is also causing disturbance. Once the trial is completed in mid-2014, we will look at the findings and make a decision,” Mr Wilson says.

Editors notes/ Background Information:

What is the problem?
Excessive noise created by engine braking near homes causes frustration for affected residents.

It’s estimated that only a small number of the fleet (1%) and it occurs in a variety of locations around the country.

Engine braking noise generally arises from older American designed trucks and is not an issue for new trucks, which suppress engine braking noise.

This problem is likely to be minimised over time as new trucks have quieter engine braking systems. However, the current national fleet of trucks without these enhanced engine braking systems will be operated well into the future, so dealing with the problem is still needed in the short term.

Engine braking is a safety feature on trucks and enables faster and more controlled slowing of trucks. Engine braking systems are automatic and have to be manually over ridden by the driver.

Tauranga trial
Takitimu Drive in Tauranga will be involved in a trial whereby vehicles will be identified by the electronic system and the associated operators will be approached to seek their cooperation to help reduce this problem.

The location of the noise camera is on SH 2 Takitimu Drive near the Elizabeth St roundabout.

The camera itself is revolutionary for NZ, combining both the ability to measure the character of noise made by the heavy vehicle with the ability to record the license plate of the vehicle.

The key equipment is from the UK and Australia. The camera has now been installed following testing and software finalising.

The cost to implement the first installation of this new technology is $100k. The equipment may be moved to other locations following the trial.

Heavy vehicle noise
Noise from heavy vehicles comes from several sources. Supplementary braking systems, such as engine brakes, are only one of the sources of heavy vehicle noise. The loudest source of noise at any particular moment depends on the type of heavy vehicle and the speed it is travelling. Below about 50km/h, the engine noise is usually the loudest component. At higher speeds the noise from the tyres on the road surface becomes louder.

Some types of engine brakes are significantly louder and more disturbing than normal heavy vehicle noise, whereas other types of supplementary brakes cannot be distinguished from the general engine noise. It is therefore important to identify the source of the noise causing disturbance before taking action.

An exhaust silencer/muffler reduces the sound of engine brakes through a resonant system and does not significantly affect the brake or engine performance.

Modified or missing silencers can result in disturbing engine braking noise.

Why do heavy vehicles need supplementary brakes?

Supplementary braking systems are provided on heavy vehicles to assist the normal service brakes in maintaining safe speeds travelling down hills. Service brakes alone must meet stopping requirements. However, many vehicles are operated in a manner such that service brakes used alone may suffer overheating or excessive wear which could lead to failure on long, steep roads.

Heavy vehicle drivers also use supplementary brakes in other situations, particularly at higher speeds, to reduce brake wear. Supplementary brakes are not needed at lower speeds.

There are engine braking systems available that are not audible above general heavy vehicle noise.

What are supplementary brakes?

There are three main types of supplementary braking systems, namely:

  • exhaust brakes: a device intermittently blocking the exhaust to create back pressure on the engine
  • engine brakes: a device releasing compressed gases from the engine (often called ‘Jake’ brakes, although the name comes from the specific brand Jacobs)
  • retarders: electric or hydrodynamic devices installed in the driveline. 

Engine brakes are typically used on large trucks, whereas exhaust brakes are common on medium trucks.

Why do engine and exhaust brakes cause noise disturbance?

Engine and exhaust brakes give rise to a series of pulses of noise, which can have a distinctive sound often described as a ‘machine gun’ or ‘barking’ noise. For some systems the noise from these pulses is substantially louder than other heavy vehicle noise and can cause significant disturbance.


In locations where there is regular disturbance from engine braking noise, which cannot be resolved through liaison with vehicle operators, legislation enables control by different bodies:

  • The Land Transport Act has recently been amended to allow all road controlling authorities, including the NZTA, to prohibit or restrict engine braking in any area where the permanent speed limit does not exceed 70km/h.
  • The Local Government Act allows territorial authorities to prohibit the use of engine brakes on local roads (not applicable to state highways).
  • Land Transport Rules allow the Police to act if noise from any vehicle is excessive.
  • The Resource Management Act could allow controls on engine braking noise in situations such as specific trucks using local roads to access a particular quarry.
  • Safety is an important factor when considering prohibition of engine braking on a section of road. On local roads at lower speeds, prohibition of engine braking should not conflict with safety. On state highways, particularly motorways and expressways, it is more likely that prohibition of engine braking will conflict with safety (also considering most vehicles with engine brakes are not noisy).

For more information please contact:

Glenda Dobbyn
Media Manager
Waikato and Bay of Plenty region
NZ Transport Agency

T: 07 928 7908
M: 021 021 67217

The NZ Transport Agency works to create transport solutions for all New Zealanders - from helping new drivers earn their licences, to leading safety campaigns to investing in public transport, state highways and local roads.