What is a Road Train?

by Vintage Road Haulage, Perth WA

Australia has lots of road trains so it’s worth explaining them…

A Road Train is a commonly used Australian expression used to describe a prime mover that pulls two or more trailers or semi-trailers. The trailers are known as dog or pup trailers because they were historically used at dog farms. Australia has the longest and heaviest road-legal road trains in the world, weighing up to 200 tonnes. They regularly transport freight across some of the harshest environments on earth.

Road Trains in Australia

In Australia, the term road train covers a wide range of prime movers pulling a variety of trailers. There are 3 categories of road trains or B-Doubles which are allowed to drive on the road in Australia. These include:

Category 1
B-Double – The B-Double or B-Train is often confused with being a road train. It is made up of a prime mover which pulls two semi-trailers, which are linked by a fifth wheel and can be up to 26 metres long. The fifth wheel coupling can be found at the end of the first semi-trailer and provides more stability to the unit than a road train can. The lead semi-trailer has a turntable at the end, so it can connect to another semi-trailer without a converter dolly, which a road train does need.

Category 2
B-Triple Road Train – a B-triple road train is the same as a B-Double, but it has two lead trailers at the front.
Double Road Train – a double road train consists of a prime mover, a semi-trailer and a five axle dog trailer.
AB-Triple Road Train – an AB-triple road train consists of a prime mover, a semi-trailer, a converter dolly and a B-double.
BAB-Quad Road Train – a BAB-quad road train consists of two B-double units joined together with a converter dolly.

Category 3
Triple Road Train – a triple road train consists of a prime mover and three semi-trailers and two converter dolly’s.

Different Trailer Configurations

Semi-Trailer – a semi-trailer has the axle group at the rear of the trailer and can carry a load.
Pig Trailer – a pig trailer has the axle group near the centre of the trailer and can carry a load.
Converter Dolly – a converter dolly is a small trailer which can carry some load. It has a drawbar connection at the front and makes up part of a road train.
Dog/Pup Trailer – A pup trailer can have five or six axles and is either a fixed or converter dolly attached to a semi-trailer.

Maximum Lengths for Each Type of Road Train or B-Double

Category 1 – (B-Double) has a maximum length of 27.5 metres.
Category 2 – (B-Triple Road Train, Double Road Train, AB-Triple Road Train, BAB-Quad Road Train, BAB-Quad Road Train) has a maximum length of 36.5 metres.
Category 3 – (Triple Road Train) has a maximum length of 53.5 metres.

See the longest road train in Australia!

Road Train Transport Services for Perth & WA

Vintage Road Haulage has a fleet of trucks and road trains to transport freight all over Western Australia. Please call (08) 9410 1726 or email using the contact form.

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Need Road Train Services in WA?

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