Trailer types and definitions

Listed below are definitions of the various trailers and the corresponding inspection sheet for these trailer types:

Box (pig) trailer

A box (pig) trailer:
- has 1 axle group or a single axle near the middle of its load carrying surface
- is connected to the towing vehicle by a drawbar.
Complete pig trailer inspection sheet (F3123).

Image of side view of a pig trailer
Caption—an example of a box (pig) trailer

A dog trailer has:
- 1 axle group or a single axle at the front that is being steered by connection to a towing vehicle by a drawbar
- 1 axle group or a single axle at the rear.
This includes a trailer consisting of a semi-trailer and converter dolly.
Complete dog trailer inspection sheet (F3148).

Image showing example of a dog trailer
Caption—an example of a dog trailer

A semi-trailer has:
- 1 axle group or a single axle towards the rear
- a means of attachment to a prime mover that results in some of the mass of the trailer's load being imposed on the prime mover.
Complete semi-trailer/gooseneck type trailer (with fifth wheel or ball coupling) inspection sheet (F3128).

Image of side view of a semi-trailer
Caption—an example of a semi-trailer

A lead/middle trailer is a semi-trailer with a turntable mounted over the axle group at the rear of a trailer.
Complete semi-trailer/gooseneck type trailer (with fifth wheel or ball coupling) inspection sheet (F3128).

Image showing the side view of an example of a lead/middle trailer
Caption—an example of a lead/middle trailer

A converter dolly trailer is a pig trailer with a fifth wheel coupling designed to convert a semi-trailer into a dog trailer.
Complete converter dolly inspection sheet (F3646).

Image showing the side view of a converter dolly trailer
Caption—an example of a converter dolly trailer

A low loader dolly is a device for distributing mass that:
- is usually coupled between a prime mover and low loader
- consists of a rigid frame in a gooseneck shape
- does not directly carry any load
- is equipped with 1 or more axles, a kingpin and a fifth wheel coupling.
Complete heavy haulage/low loader/dolly inspection sheet (F3154).

Caption—an example of a low loader dolly

Caption—an example of a low loader trailer

A tag trailer:
- has 1 axle group or a single axle towards the rear of its load carrying surface
- is connected to a towing vehicle by a drawbar.
Complete semi-trailer/gooseneck type trailer (with fifth wheel or ball coupling) inspection sheet (F3128).

Image of side view of a tag trailer
Caption—an example of a tag trailer

A caravan is an enclosed trailer designed for people to live in (includes camper trailers).
Complete pig trailer inspection sheet (F3123).
A caravan or camper trailer must be equipped with cooking facilities, living or sleeping accommodation.
A caravan or camper trailer (including pop-top camper trailer) must have outward-opening or sliding doors. At least 1 door must be located on the left-hand side or at the rear. There is no requirement for doors on trailer-based fold out campers.
A caravan or camper trailer designed primarily for human occupation (when stationary) must be fitted with a fire extinguisher. When conducting an inspection on a caravan or camper trailer, it is not a requirement to check the safety or validity of the fire extinguisher.

Image showing the front and side view of a caravan
Caption—an example of a caravan

A mobile equipment or mobile machinery trailer:
- has permanently attached equipment that performs specific tasks
- is not able to carry a load with the exception of any auxiliary equipment for performing the function for which they are designed
- must be registered with a registration category of STRL (e.g. a compressor trailer)
- requires a weighbridge certificate/supervised weigh documentation.
Complete pig trailer inspection sheet (F3123).

Image showing the front and side view of a mobile equipment trailer
Caption—an example of a mobile equipment trailer