A load of 10 tonnes carried on a rigid truck with no headboard is secured by two tie downs. What must the combined strength of the tie downs be? A load of 10 tonnes carried on a rigid truck with no headboard is secured by two tie downs. What must the combined strength of the tie downs be?

  • A. 5 tonnes

  • B. 10 tonnes

  • C. 15 tonnes

  • D. 20 tonnes

  •  
    The correct answer is D
     
    Correct. The lashings must be able to withstand twice the load weight.
     
 
 
 

Heavy vehicle weights and loads

The tare weight is the weight of the vehicle itself, not including any load. Gross weight is the combined weight of a vehicle and its load, accessories and equipment. Before an overweight vehicle or load can be used on the road, the driver must obtain an overweight permit, which must be carried in the vehicle. You can get one from your local NZTA office.

Lashings and tie downs

lashings on a truck carrying concrete pipes

You can see in this image that the front pipe has two lashings through it to stop it rolling. The pipe is blocked by another concrete platter at the front and has chocks to also help prevent it shifting (these are small wooden blocks in a triangle shape. The load is distributed so that the centre of the heaviest part of the load (the two pipes) is just in front of the rear axle.

The combined rated strength of lashings or tie downs placed over rigid loads on heavy motor vehicles where loaded against a headboard must exceed that of the load.

The combined rated strength of lashings or tie downs placed over rigid loads on heavy motor vehicles where not loaded against a headboard must exceed twice that of the load.

For sideways forces, the load restraint system must be able to take at least half the weight of the load to keep it secure.

Anchor points to which lashings are secured must have a strength of at least the same strength as the lashings

Uncovered loose bulk loads

truck trailer with covered load

Uncovered, loose bulk loads are liable to fall from the vehicle if they are higher than 100mm below the height of the vehicle body.

They should be covered with a tarp or other cover to stop them blowing away, as can be seen above with this truck and trailer carting soil.

Axle loads

There are three types of axle: single (S), single large-tyred (SL) and twin-tyred (T).

The maximum load on a single standard-tyred axle is 6000kg - you can see an example in the top image.

The maximum load on a single large-tyred axle is 7200kg.

The maximum load on a twin-tyred axle is 8200kg.

single-axle-set

Weights must be distributed so that at least 20% of the load remains over the front wheels. This is especially important in vehicles with a large rear overhang. When there's not enough weight over the front wheels, steering performance is reduced and the vehicle is more likely to understeer (continue straight ahead even though the wheels are turned).

This axle loading diagram shows how much weight various combinations of tandem axles can take.

axle-loading-diagram

Tri-axle sets can take even more.

tri-axle-set

An quad axle sets, often seen on tankers can carry up to 20,000kg.

quad-axle-set

The complete list of axle loads is available in this leaflet from NZTA.

Checking the load

Before setting off you will need to check for load security, load height, load width and load weight. It is the driver's responsibility to check that the load is secure and correctly loaded. It is not a legal requirement to perform a pre-trip inspection, however, it is highly recommended and there may be some legal obligations you have because of the load you are carrying, such as affixing the correct hazardous goods signs, or attaching over-dimension flags.

After driving on an uneven surface you should check your load as it may have moved or the lashings may have loosened. You should also check your load after each rest stop.

Loading certificate

A loading certificate (or certificate of loading) must contain the tare weight in kg, the gross laden weight in kg, the gross combination weight in kg (if the vehicle has a towing connection) and static roll threshold height and weight limits (when laden or unladen, most goods service vehicles with a maximum gross vehicle mass (GVM) exceeding 12 tonnes must have a static roll threshold (SRT) of at least 0.35 g (where g is the acceleration due to gravity)). If it's a passenger vehicle it will show the seating capacity.

certificate-of-loading