1.1 – Why Restrain – Safety

If you have a vehicle, particularly a heavy vehicle, and you do not adequately restrain a load you place on the vehicle, the load may move during your journey. This movement would be caused by normal forces placed on the load from changes in speed due to acceleration and braking, cornering and uneven or sloping road surfaces and even the air flow over the vehicle.

Click on the animations below to display what can happen to your load

Acceleration and Braking
Uneven Surface
Slopng Surface – Hill
Sloping Surface – Camber

The magnitudes of these forces are large enough that the weight of the load is not sufficient to resist them. This is true regardless of how heavy the load is because the forces on the load increase with the weight of the load.

As a result, all loads need to be restrained to make them safe and larger loads require more restraint, to stop them moving.

Freight Dislodgement (Fig 10 Load Restraint Guide)

If the load moves it can potentially fall off the vehicle or cause the vehicle to be unstable and roll over.

At minimum this is likely to cause property damage, and also places the lives of other road users in danger either directly from the load or vehicle or indirectly through swerving to avoid it.

Moving loads also pose a risk to the drivers and passengers in the vehicle by piercing or crushing the cabin

As a result, proper restraint of loads is a very important aspect of both Public Safety and Workplace Safety.

Safety while loading and unloading

In addition to the on-road risks associated with inadequate restraint of heavy vehicle loads, the acts of loading and unloading a vehicle present their own sets of risks. These risks also need to be considered when planning how to move a load from one place to another.

Safety while driving
In addition to correctly restraining the load on road safety also requires drivers to recognise that the characteristics of the vehicle have charged due to the load and that the routes that the vehicle can safely drive on may also change as a result of the addition of the load.

It is important that drivers understand the effect that the mass, size, and positioning of the load can have on the vehicle’s stability, steering and braking.

In particular:

  • A higher centre of gravity will reduce stability and increase the risk of rollover.
  • An unevenly distributed load across the width of the trailer will reduce the vehicle’s stability when cornering.

Unbalanced load (Figure 186 Load Restraint Guide)

Vehicles carrying “live” loads (loads that can move) are more likely to overturn on corners. This includes bulk liquids, livestock, hanging meat, wet concrete, motor vehicles and large rubber-tyred equipment.

Bulk Liquids (Fig 203 Load restraint guide)
Large Rubber Tyred Equipement (Fig 290 Load Restre

If a load isn’t evenly distributed along the length of the trailer, and there is more weight on some wheels than others, then each wheel will not brake with the same force. This can cause the wheels to lock up.

Offset centre of gravity
  • Braking forces can be greater at low speed because of the “grabbing” effect.
  • External factors such as high wind speeds can also reduce vehicle stability or blow the load off.
    It is therefore important that drivers:
  • Are aware of the height and width of the loaded vehicle.
  • Understand the constraints of the route they are traveling on and any specific access limitations on the vehicle.
    • E.g. Make allowances for high and wide loads when driving around corners, under bridges and electric cables and near power poles, traffic lights and other obstructions.
Low Clearance Bridge and Electric Cables
  • Drive at an appropriate speed for the driving conditions.
  • Exercise appropriate caution on corners.
  • Are suitably trained (eg attend rollover prevention program)
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