What are custom trailers?

Posted on: 11 January 2020

There are a wide range of custom trailers available, used for different purposes and different workloads and having very specific technical requirements. Different states in Australia have different laws covering these requirements. This means that anyone using a custom trailer to travel to different parts of Australia needs to make sure that they comply with different state laws.

Types of custom trailer

There are three types of trailer that relate to where the axle and tyres are based. The pig trailer is where the wheels and axle are based in the centre of the trailer, with an equal load on either side. A dog trailer has two sets of axles and wheels, one at the front and one at the back of the trailer.

The third type of custom trailer is what is known as a semi trailer. This is where it has one set of axles and tyres at the back of the trailer, and the front is physically attached to the vehicle towing it.

Specific purpose trailers

There are a number of custom trailers that either have specific purposes or are used to carry very specific types of loads. Some of these are referred to as enclosed trailers, which are normally caravans but can also include mobile kitchens or mobile offices.

Other types of specific purpose trailers include trailers that are used to carry boats, cars, horses and a wide range of plant machinery.

Many of these requirements can seem a bit overwhelming and there are good areas of support online, including many excellent discussion forums where a lot of questions can be answered.

Trailer categories

Custom trailers, including all of the above, are normally categorised by tonnage, which plays a key role in determining technical and legal requirements. Trailers will normally be categorised either as very light, light or as a medium trailer.


On all types of custom trailers, lighting is one of the most important elements to get right, both from a safety and a legal standpoint. The technical requirements will normally cover the type of lamp itself, the colour of emitted light and whether or not it conforms to certain legal and international regulations.

There are normally a significant number of different types of lamps that need to be configured. These include a front position lamp, a rear position lamp, a rear stop lamp, a direction indicator lamp, a rear registration plate lamp and a hazard warning signal.

There will also need to be reversing lights fitted that act in co-ordination with all other lighting.

Electrical wiring

All custom trailers will need to have extensive electrical wiring fitted, running from the main vehicle through to the back of the trailer. The scope of the wiring will be determined by the nature and length of the trailer, but there are a few general principles that need to be observed.

All electrical wiring needs to be insulated at points where it joins together. The wiring must be placed in such a way that it cannot come into contact with any moving parts and cannot overheat.


Depending upon the size and tonnage of the trailer, it will need to have additional braking fitted. This must be completely controllable by the driver of the vehicle that is towing the trailer.


Using any custom trailer means that additional safeguards need to be in place in order to make sure that the vehicle and trailer are driven as safely as possible. This can include things such as using safety chains on the tyres where necessary, having wheel guards in place and ensuring that the driver has clear visibility of the trailer at all times.