2.1 – Understanding the Load – Weight Dimensions and Centre of Gravity


In order to work out how to restrain you load adequately you need to know its weight. Not only will the weight of the load determine the vehicle you choose, the loading performance standards specify the amount of force the restraints need to provide in terms of fractions of the weight.

These forces can be provided by friction in the case of the tie down method or directly via vehicle structures or lashings in the case of direct restraint.

If you do not know the weight of the load you cannot work out how many restraints you need to adequately restrain it.

Sometimes, working out the weight of an item is easy.

  • The customer may already know the weight of the load,
  • in other cases in may just involve reading a the label on the load the manufacturers plate on a vehicle or searching on the internet
  • In other cases, you will need to use documents such as a manifest, do some simple calculations, or use
  • In other cases, you will need to use documents such as a manifest, do some simple calculations, or use equipment such as a forklift (fitted with scales), or a weighbridge.

Manifest and Container weight declarations

Where shipping containers are sealed it may be difficult to determine the weight of the container. To address this issue the Heavy Vehicle National Law (and WA and NT legislation) requires the use of Container Weight Declarations (CWDs) to record the weight of the load they are carrying. These legal provisions also impose chain of responsibility obligations on all parties in the transport chain. If you are using CWDs please note that they may not be reliable -click here

When calculating the weight of the load for:

  • Multiple items- add up the individual weights of the components of the load
  • Bulk items: multiply volume of vehicle by density of the product (or maybe in some cases divide the vehicle capacity by the density to calculate the volume you can load
  • Volumetric loading schemes for livestock – Under these schemes the volume of the vehicle is used to calculate the number of animals that can be loaded onto the vehicle based on estimates of the average animal weight.

Checking with a weighbridge

Checking load using a weighbridge


The dimensions of a load can have a significant impact on the choice of vehicle and load restraint.
Any staff member taking an order for a transport task should determine the dimensions of the load and whether there is:

  • A loading plan available, and/or
  • Any requirements for the load to be kept upright.

General access vehicles are typically less than 12.5 m long, 2.5 m wide, and 4.2 m high for a rigid truck. If the vehicle and load combined exceed these dimensions, consideration needs to be given to choosing an articulated vehicle which may be up to 19 m long, or a restricted access vehicle (mouseover on restricted access vehicle Compliance and Enforcement bulletin 1 – Restricted access vehicles (nhvr.gov.au) Restricted access vehicles may be required to travel under a notice, or permit or have other limitations on where it is permitted to travel.

Details of the dimension requirements for different vehicle types is available on the NHVR web site. National heavy vehicle general dimension requirements (nhvr.gov.au)

Any requirements for it to be kept upright can also impact on the load restraint requirements.
The stability of the load is optimised if it can be kept as low as possible. Some loads can simly be loaded a different way up to make them more stable. However, if the nature of the load requires that it needs to stay oriented in one direction (“This way up”) the ratio of the height to the width and length needs to be considered.

Where the length is less than 80% of the height or the width of the base is less than 50% of the height the load is at increased risk of toppling.

Unstable forwards
Unstable sideways

In these situations consideration should be given to rotating the load or using specific strategies to restrain the load which will increase its stability.

These might include using a rated headboard, direct restraint, or attaching loads together. In these cases, consideration of stretching of the restraints needs to be considered when designing an approach to restraining the load.

Centre of Gravity

Attaching a load to a vehicle will raise the centre of gravity of the combined vehicle and load.

This means that the risk of the laden vehicle rolling over will increase. Understanding the mass of the load and where its centre of gravity is will be critical for determining the centre of gravity of the combined vehicle and load which is in turn used to calculate the risk of a roll over.

With loads that are not uniform in density, it may be very difficult to understand where the centre of gravity of the load is located.

This is particularly important for tall loads and loads that are top heavy or oddly shaped. This issue will be discussed further in Lesson 3.1

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