Resources

Heavy rigid vehicle stability and dynamics: an introduction programme for drivers of heavy motor vehicles

5.   Load security

• 5.1   Load security legislation
• 5.2   Load distribution and arrangement on vehicles
• 5.3   Rated strength of vertical securing devices for rigid loads on heavy motor vehicles
• 5.4   Anchor points
• 5.5   Loose bulk loads
• 5.6   Basic safety principles

The Truck loading code sets minimum standards for load restraint and operators must familiarise themselves with it. These standards are designed to prevent load shift under normal operating conditions, including braking, acceleration, cornering and movement over uneven ground.

Any load that shifts will decrease vehicle stability dramatically, particularly during braking and cornering. Any loads positioned more than 100 millimetres away from the curtains or sides of a vehicle must be restrained in accordance with the Truck loading code to prevent load shift during cornering.

Loads carried on a vehicle must be restrained according to the following basic rules. Restraints must:

• be able to take the full weight of the load in a forward direction, and
• be able to take half the weight of the load in a sideways direction, and
• be able to take half the weight of the load in a rearwards direction, and
• prevent vertical movement.

The responsibility for loading the vehicle correctly including making sure it is secured to the minimum requirements, as shown in the Truck loading code, rests with the driver. The responsibility starts at the time of loading. Placing loads that increase the height of the vehicle's CG or shifts it off-centre (closer to one side) will reduce the vehicle's stability and dramatically affect its handling.

Drivers of vehicles that have a high CG must drive more carefully, especially around curves.

5.1   Load security legislation

• The Land Transport Act 1998 contains the load security legislation that is administered by Land Transport New Zealand and enforced by the NZ Police. It provides strict liability for offences involving insecure loads and loads falling from vehicles. Offences attract fines for an individual of up to $2,000 and a licence may be disqualified for a period as the court thinks fit. The maximum fine for a body corporate is $10,000.

5.2   Load distribution and arrangement on vehicles

• The first priority with any load is to keep within the maximum legal weight limits and vehicle dimensions. The load should be placed against the headboard if this can be done, provided the handling of the vehicle is not impaired. If the load cannot be placed against the headboard, baulking should be used or twice the strength of lashings are required.
• The load should be spread to keep the centre of gravity as low as possible. Where the load is stacked, larger and heavier items should be placed at the bottom. The vehicle should be loaded to give correct axle distribution and an even weight distribution over its floor area.
• In order to maintain lateral stability the centre of gravity of the load should be on, or as near as possible to, the centre line of the vehicle. It is better for heavier items to be carried on the centre line of the vehicle than at the sides.
• Throughout the journey, at every stop, (including after a rest stop) the load should be checked for security and the lashings tested. Weather conditions can affect the tension of ropes and this may lead to damage of the load or loss of security.

5.3   Rated strength of vertical securing devices for rigid loads on heavy motor vehicles

A   Combined rated strength = 2W

Securing devices (lashings) have a combined rated strength of at least twice the weight of the load where not loaded against a headboard.

B   Combined rated strength = W

Securing devices (lashings) have a combined rated strength of at least the weight of the load where packets are loaded against a headboard, such that the top packets have at least 150 mm supported.

C   Combined rated strength = 1½W

Securing devices (lashings) have a combined rated strength of at least one and a half times the weight of the load, where lower packets are supported by a headboard but upper packets are not supported by at least 150 mm.

Failure of the load restraint could result in the load developing sufficient momentum, if allowed to slide, to demolish the headboard or other abutment with potentially serious consequences.

5.4   Anchor points

Traditional rope hooks or rings, and the method by which they are attached to the vehicle structure, cannot be relied upon for the restraint of other than light loads. For this reason, platform vehicles in particular should be equipped with load anchorage points, so designed and integrated into the structure that the maximum forces likely to be imposed on them are transmitted to the main chassis frame of the vehicle. It is common practice to utilise the coaming tie rails and, in this case, it is necessary to tie in the vicinity of the cross member and tie rail junctions to prevent distortion of the tie rail.

Each anchor point must have strength at least equal to the rated strength of the lashings secured.

5.5   Loose bulk loads

Loose bulk loads can generally be described as having a nature which does not readily lend itself to any form of packaging or containerisation, eg sand, aggregate, shingle, rubble, rubbish, asphalt and other similar materials.

Clearly, the loading and securing of such loads do not pose the many problems associated with general freight, but nevertheless they do have security problems peculiar to themselves.

5.6   Basic safety principles

• The maximum vehicle and axle weights must never be exceeded.
• Loose bulk loads that are liable to fall from the vehicle and which do not have a tarpaulin fitted, should at no time be higher than 100 mm below any side of the body in which the load is being transported. If the load is heaped to its own natural ‘angle of repose’, this could result in load shedding due to the vehicle's movement.
• Doors to bulk bins must be closed to avoid loose bulk loads from being blown out.
• As these loads normally rely upon the vehicle body for restraint, it becomes extremely important to ensure all body-to-chassis attachment points. eg ‘U’ bolts, hinge pins, hinge pin brackets, are always secure and that these and the body are in sound condition.
• Loose bulk loads should be covered with a tarpaulin, netted or sheeted as appropriate whenever there is a risk of load shedding due to wind action or movement.