Opinion:
Driving the highways in NSW you would have seen the signs countless times, underneath an
illustration of a truck: “Please Limit Compression Braking”.
Or the sign might say something like “Avoid Compression Braking in Residential Areas”.
Unfortunately many truck drivers ignore these signs. It’s not against the law – the signs are
advisory only -- but the consequences for residents nearby can range from mere annoyance
to disturbed sleep at night, with all the implications that brings for normal human functioning.
It seems to me that it’s often a grey area as to whether it’s better to have engine brake
noise near someone’s house, or the increased risk of a truck parking in their lounge room.
We’ve all heard the funny prank call from a radio host to an understandably cranky truckie who thinks it’s a government official telling him not to use his engine brakes.
But let’s face it -- some truck drivers really are totally inconsiderate, including towards their own colleagues.
I’ve known them to drive past what were obviously our driver bunk rooms in a transport depot with their engine brakes on. Sometimes they do the same coming into truck rest areas and truck-stops, or just in the yard while others might be trying to sleep in their trucks. They are not the type who will weigh up whether they really need to use the engine brakes in “built-up” areas, including approaching a set of lights on perfectly flat road at midnight.
Some sort of compression braking is obviously essential for trucks going down steep hills with speed limits of 40 or 60 km/h. But for short stretches in 80 or 100 km/h speed limit areas, I’m not so sure.
The basic dilemma is that while American-style engine brakes help slow down a truck on a
downhill stretch of road, their “bark” can often make a hell of a lot of noise.
There’s not much information on this huge issue for residents who live near a highway on a
hill.
And there’s not much information for us truck drivers either. So here’s an amateur explainer from what little public information is out there, and the experience of myself and some
other old-timer mates.
There are three main types of compression braking I’m aware of that are used in trucks in Australia.
One is exhaust braking, which is fairly quiet, and also fairly weak, but good enough for smaller trucks.
Another is the transmission retarder, using oil and the gearbox to slow down the drive wheels. The Scania and Isuzu transmission retarders are so strong you don’t need to use the foot brakes at all, but they have potential downsides including extra weight, cost and maintenance.
The third type – and by far the loudest – is the trusty old engine braking system (but which
I’ve been told can be hard on diff bushes).
I drive a Kenworth T610 built at American parent company PACCAR’s manufacturing plant at
Bayswater in Melbourne, and it’s a beauty, but it’s got (legally) loud engine brakes which I
have a love/hate relationship with.
These are called “Jake Brakes”, or more accurately “Jacobs Brakes”, named after a fellow
American company.
The Jake Brake in the Cummins motor operates when your foot is off the accelerator pedal.
When the Jake is on, it allows highly compressed air to be dumped into the exhaust rather
than powering the pistons in the cylinders.
Normally the 15 litre Cummins sits on a little over 1500rpm at 100km/h while powering on
the open road. That’s in the top gear of 18 in the Eaton gearbox.
The Jake Brake works best near the high revs mark of 2000rpm – any more and you might
blow up the engine.
To achieve the maximum engine braking effect, at 100km/h you need to be in 17th gear.
Better still – but also louder still – is 16th gear. To keep the truck at lower speeds, you need
to be in lower gears.
The advantage of all this is that you don’t have to rely on the foot brakes.
For the uninitiated, in big trucks when you put your foot on the brake pedal, compressed air
forces brake pads against either a disc or a drum in the wheels of both the prime mover and
trailers.
If you rely too much on the foot brakes on a long steep hill, you could run out of air. When
that happens, the truck doesn’t career out of control, it just stops, with the brakes locked
on. That risks someone running up the back of you. This once happened to a mate of mine
who was riding the foot brakes too much down the old Toowoomba Range
More dangerous is what truckies call “brake fade”, which is when the brakes heat up so
much from overuse over a short time, they don’t work properly. You don’t hear about this
so much these days, but I’ve heard mechanical experts say this is especially the risk with the
older-style drum brakes.
That’s why trucks going down very steep hills, such as Victoria Pass in the Blue Mountains and Mount Ousley near Wollongong, are limited to 40km/h, and you are only allowed to tap the foot brakes twice. This rule forces the driver to be in a low gear and using some type of compression braking.
On less steep and shorter grades at 60, 80, or 100km/h, depending on the situation, I don’t think engine brakes are essential for safety, but they are very handy for saving brake pad wear and therefore money. They are also handy for bleeding off speed to avoid being booked.
At times it’s simply just easier to leave the engine brakes on rather than lifting your foot
onto the brake pedal. So there can be a bit of laziness involved near residential areas.
(By the way, you have to be really careful using compression braking in the wet, because the
trailers might want to come around in front of the harder-braking prime mover.)
No matter the situation for the truck driver, the common problem for nearby residents is
there are nearly 20-year-old noise decibel limits on truck engine brake systems which can’t
be directly checked during annual mechanical inspections.
Old trucks are the main culprits and there are apparently some shonky truck operators out
there who even muck around with the mufflers to get more power, at the cost of more
noise, with the seemingly low risk of getting caught during a random weighbridge inspection.
Back in 2019 Wollongong then-Opposition state Labor MP Ryan Park complained to the
Illawarra Mercury newspaper that a noise camera in place on long, steep Mt Ousley for a
decade had not resulted in a single fine.
"The government continues to hide behind the excuse that no jurisdictional powers exist to
enforce non-compliance with brake noise standards in NSW," Mr Park was quoted as saying.
In response the newspaper quoted a government spokesman as saying: "Transport for NSW has been working with the National Transport Commission and other states on developing a national in-service standard to detect excessive engine compression brake noise."
What’s Ryan Park’s view on the issue now that he is actually part of the Government in NSW?
I spoke with one of his staff who said the last they heard, use of noise cameras needed the
updated national standard on engine brake noise, which still hasn’t arrived, years later.
I contacted the National Transport Commission which is supposed to be coming up with the
new standard, and they didn’t reply.
Meanwhile in 2021 Wollongong Council sent a letter to the NSW Government asking for a
review of the controls, limits and enforcement of engine brake noise in residential areas.
A council spokesperson told me they didn’t get a response to the letter, and haven’t heard
anything from the current Government either.
Meanwhile Transport for NSW says on its website that it “strongly advocates tighter vehicle noise standards”.
“The worst problems occur when drivers use their engine brakes unnecessarily near built up
areas, especially at night when residents are trying to sleep,” says the website.
“Trucking is an important business. But the constant use of noisy engine brakes hurts the industry's image.”
However there’s good news on the website too: “This noise source has however been
progressively reducing over the years partly due to quieter technology on the newer
generation of heavy vehicles and fleet renewal that occurs with time.”
For those truck owners who might be doing the wrong thing: “Transport for NSW
completes periodic inspection of heavy vehicles at testing stations to ensure that
silencers and emission systems are fitted and maintained. Inspections are also carried
out during yearly or half yearly vehicles registration.”
And an NHVR inspector told me recently that in NSW at least, if a truck that would wake
the dead is reported to the NHVR or Environment Protection Authority twice, it is called in for an inspection.
Boiling it all down, I reckon I’ve worked out the engine braking grey areas, in NSW at least.
This is just my theory but if there is a 40 or 60 km/h trucks-only limit – and no sign urging engine brake restraint – the authorities reckon you need engine brakes. (That’s the situation at the bottom end of Ryde Road in Sydney. So to avoid waking people up in the early hours, I go down the less steep bottom end of Pennant Hills Road instead, only touching the foot brakes occasionally.)
But if there is a “Please Limit Compression Braking” sign somewhere, I reckon the authorities figure you don’t really need the engine brakes – but they also don’t want to be liable if you end up in someone’s front yard.
If you found this article informative please consider donating:
Comments