The freight containers mainly transported are constructed to international standards (ISO) and are identifiable as such by their external markings (refer AS/NZS 3711 Pts 1-10).
They are made to nominal lengths of 12 metres, 6 metres and 3 metres with a width of 2.4 metres and heights of 2.4 metres, 2.6 metres and 2.9 metres.
It is essential that the driver checks the overall height of the vehicle from the ground with respect to bridge heights and overhead obstructions expected en route. Vehicles carrying empty containers ride higher than loaded containers. Fleet operators will find a height loading gauge useful at yard exits.
A feature of all the containers mentioned above is they are equipped with specially designed corner castings that are provided for both lifting purposes and as a means of securing the container when it is being transported. There are also containers that are not built to these standards. These containers may be secured by specially designed restraint systems.
Safe methods for the carriage of containers will therefore vary according to the type being transported and the securing attachments provided on the carrying vehicles.
As mentioned above ISO containers are fitted with a casting at each corner. This enables them to be securely attached to the carrying vehicle by means of specially designed locking devices known as 'twist locks' (see figure 17). A vehicle properly equipped for carrying containers has twist locks built into its structure at appropriate spacings to line up with the corner castings on the container(s) that it is designed to carry. Provided the twist locks are then fully engaged and properly locked, the container may be regarded as being secure.
Where provision is made for the use of twist locks they should always be used. Advantage should be taken of any adequate inbuilt locking device.
Figure 17 Typical twist lock or tie down instalment
It is important that all vehicles used to carry containers are fitted with a securing device.
A container should never be carried when insecure, whether it is loaded or otherwise. Securing devices other than twist locks should be of an acceptable configuration (see figure 18). Ropes, chains or webbing should only be used for securing sea freighter containers and newsprint bases.
As explained elsewhere in this code, a load carried on a vehicle without the use of restraining devices will not be secure because the frictional restraint between those parts of the load in contact with the platform of the vehicle will not always prevent it moving when the vehicle brakes or changes direction.
Adaptor frames are sometimes used. Adaptor frames usually incorporate twist locks. Frames should be suitably bolted or securely fixed through to the chassis. If in an emergency a need arises to carry a container on a vehicle not specifically designed for that purpose, the container must be secured in a manner defined for large indivisible loads (see Construction equipment).
Lashing or securing devices used should only be attached to those fitments on the container intended to facilitate its lifting or mechanical handling when laden, eg lashing rings or corner castings on cargo flats. These fitments should be examined to ensure that they are in sound condition, and all of them should be used to secure the container to the vehicle platform.
The number of anchor points used will be decided by:
There should never be less than four anchor points used in any circumstances, ie two per side.
It is essential that the stresses transmitted by the securing devices are ultimately absorbed by the vehicle's chassis frame. Anchorages must therefore be fixed securely. Each anchorage should be capable of withstanding its rated capacity acting in the direction of the side members within an included angle of 10° to 60° to the horizontal. To achieve this it may be necessary to strengthen cross members by the use of stays or bracing secured to the vehicle's chassis. Rope hooks are not strong enough for anchorages and must on no account be used for this purpose. Chaining containers to the rope rail of a vehicle must not be permitted.
All devices used for securing a container should be suitably constructed in accordance with recognised engineering standards and should be adequate for the job for which they are designed.
Purpose-made restraining devices are suitable where special lifting pockets, brackets or attachments are fitted to the container. A minimum of four devices should be used and three of these should be strong enough to restrain the container if the other clamp fails to function correctly. In most cases it will be necessary to reinforce the deck of the vehicle in the vicinity of the device position, ensuring the weight is transferred to the vehicle chassis. The design of the device and the reinforcement should be carried out in accordance with the recommendations of the vehicle or trailer manufacturers.
Incorrect loading of a container may result in dangerous situations occurring when the container is handled or transported. Serious damage may be caused to the goods carried. In many instances the driver or vehicle operator will have no control over the packing of a container and will not be able to inspect its contents when accepting it for movement.
If a container is unevenly loaded with its centre of gravity offset towards one side or one end then there is a risk of it tipping when lifted. When it is loaded on the vehicle there is a risk that the vehicle's axles will be incorrectly loaded and the stability of the vehicle adversely affected. Inadequate stowing arrangements within the container may result in the load shifting, which again may cause a dangerous situation. If it is then apparent that the container has not been safely stowed, it should not be accepted.
The following general stowage principles that affect road safety must always be observed:
Figure 19 Suggested method of loading a container
The stability of vehicles carrying liquids and especially dangerous goods in tank containers is an important safety issue. Loaded tank containers should be transported on low bed trailers.
Note: It is important that the low bed trailer is fitted with twist locks.
Most shipping containers and flat platforms of all types used in road transport comply with ISO requirements. The platform container is primarily used for heavy lift and out-of-gauge cargoes. They are equipped with corner castings designed to interlock with mating twist locks for either lifting or securing them for transport.
Platform containers have load anchor points to facilitate the lashing of loads to the platform. ISO requirements specify a minimum rating of 3000kg for anchor points on the base structure and 1000kg for those located elsewhere, eg lashing rings on the platform floor. These anchor points do not require additional certification to NZS 5444 Load anchorage points for vehicles.
A platform container must be secured on a vehicle fitted with four compatible twist locks, and may be transported only if all loads on the platform are adequately secured. The twist locks must be fully engaged and properly locked. If it is not possible to adequately secure a load to the platform container, then additional lashings must be placed over the load and attached directly to the vehicle's anchor points.
Some platform containers can be stacked and secured for transport when empty by using all built-in positive lock fittings (usually twist locks or ring and bolt connections). It is important to check that the platform containers are compatible to lock together. All platform containers that meet ISO standards can be stacked and secured for transport using four interlocking double twist locks between each layer.
Note: The efficiency of the locking mechanism (crimp or seal) will dictate the strap's rated strength.
The principles of packing and stowing applicable to containers also apply to general freight vans and curtainsiders. It is important that the load cannot move relative to the vehicle. This means that contained loads within vehicles with adequate sidewall strength or curtain rating should be packed tightly together within the vehicle's body to prevent any movement, otherwise the load will need to be restrained as though it were on an open decked vehicle. Loads that are further than 100mm from the sidewall or curtain must be fully restrained. The exception is one or two small individual items that each weigh less than 25kg. Load separators such as shoring bars should be used where necessary to restrain individual items. Where parts of loads are added or removed during a journey, the load should be rearranged and re-secured to maintain correct load distribution and restraint.
Last updated: 27 August 2010