This document aims to provide heavy vehicle drivers with information about safe driving
behaviour. The information provided in this publication is not a substitute for knowing the
legislation and should not be taken as an accurate or binding interpretation of the law.
Heavy Vehicle Driver – Tips & Guide
Issue 2 - February 2012
Vehicle Ratings
Drivers of heavy vehicles must be aware of the maximum loaded capacity of their
vehicles in order to operate safely, legally, and prevent damage to both the
vehicle and the road network. Familiarise yourself with the meanings of relevant
terminology;
GVM
Gross Vehicle Mass means the maximum loaded mass allowed on a vehicle.
GCM
Gross Combination Mass means the maximum loaded mass allowed on a motor
vehicle and any vehicles (trailers) that are being towed by it.
GTM
Gross Trailer Mass means the maximum allowed mass that can be transmitted to the
ground via the axles of the trailer when the trailer is loaded and connected to a towing
vehicle.
The above ratings are what a Compliance Officer will base an assessment on to
ensure that a vehicle is suitably rated to carry a particular load.
TARE WEIGHT
This means the unladen weight of the vehicle only (no load).You should be aware of the
tare weight of your vehicle so you know the maximum load you can carry if you intend to
load to the maximum permissible weight. If you are unsure of the vehicles tare weight,
you may take the vehicle over a weighbridge when it is empty to obtain an accurate tare
weight.
If the vehicle has been legally modified under national guidelines and the rating is
upgraded, then this would be reflected on a Modified Vehicle Plate that has been fixed
to the vehicle.
Note: All modifications must be carried out by an approved certified Engineer, who must
also fit a modification plate, which will detail the modification made, including the
modified rating.
MAIN ROADS Western Australia
Tips & Guide on Vehicle Ratings – Issue 2 February 2012
If an appropriate modification plate is not fitted, the vehicle may not have been modified
and certified by an approved engineer and therefore, may not be safe. For further
information refer to Department of Transport’s requirements in the Vehicle Standards
Bulletin – VSB 6, available at:
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/index.aspx
What you need to know and check before driving a heavy vehicle
When any vehicle you drive is in excess of the mass or dimension limits
prescribed in the Road Traffic Act (Vehicle Standards) Regulations 2002 (VSRs),
the vehicle needs to be driven in accordance with a current WA Main Roads
Permit.
Check that the vehicle/s is appropriately rated by checking the Compliance /
Modification Plate on each vehicle in the combination. You must ensure that the
ratings are sufficient to carry the load that is to be transported.
You must ensure that the load is distributed evenly or correctly positioned so that
the allowed axle mass limits are not exceeded.
As an Example:
In this scenario you may be required to drive a prime mover, towing a low loader dolly
and quad axle low loader carrying earth moving machinery that weighs 48 tonnes.
The tare weight of the combination (empty) is 30 tonnes
Now add these two figures up:
Load
Tare weight of vehicle (combination)
GCM
=
48t
30t
78 tonne
An example of the weight distribution would be;
Total =
6t
18t
18t
36t
78t
(on the steer axle)
(on the drive axle group)
(on the low loader dolly axle group), and
(on the low loader axle group)
(the figures would be reflected on your permit)
The GCM rating for the prime mover must be 78 tonnes or more.
The GVM rating for the prime mover must be 24 tonnes or more.
The GTM rating for the low loader trailer must be 36 tonnes or more.
The GTM rating for the low loader dolly must be 18 tonnes or more.
MAIN ROADS Western Australia
Tips & Guide on Vehicle Ratings – Issue 2 February 2012
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