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What is an axle group?
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What are the regulated dimension limits?
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What are the regulation mass limits?
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What is a road train?
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What is a turntable/fifth wheel?
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What is a semi-trailer?
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What is a converter dolly?
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What is a pig trailer?
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What is a dog trailer?
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What is a B-double?
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What is a block truck?
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What is a trailer drawbar?
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Who can I contact for more information?
- GCM: Gross Combination Mass
- GVM: Gross Vehicle Mass
- GTM: Gross Trailer Mass
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- Is a single axle group, tandem (bogie) axle group, twinsteer axle group, tri-axle group or a quad axle group
- Different axle groups have certain requirements in relation to minimum and maximum axle spacings
- Definitions for each type of axle groups are located in the Road Traffic (Vehicle Standards) Regulations 2002
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- Vehicles can be built to or carry loads to various dimensions, which are outlined in the following:
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Axles and Tyres |
Maximum axle group load |
|
Single Steer
2 Tyres |
6.0 tonne |
|
Twin steer axle group
4 tyres |
10.0 tonne for non load sharing suspension
11.0 tonne for load sharing suspension |
|
Single axle
4 tyres |
9.0 tonne
|
|
Tandem axle group
Dual tyres (8) |
16.5 tonne
|
|
Tri-axle group
Dual tyres (12) |
20.0 tonne
18.0 tonne fitted to a pig trailer |
Vehicles must not exceed any manufacturer's limit. The least value should be noted for components such as:
- tyre rating;
- axle rating;
- gross vehicle mass (GVM);
- gross trailer mass (GTM); and
- gross combination mass (GCM).
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A combination, except a B-Double, consisting of a motor-vehicle towing at least two trailers (counting as a single trailer a converter dolly supporting a semi-trailer).
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A device (except the upper rotating element and the king pin, which are parts of a semi trailer) used with a prime mover semi-trailer, or converter dolly.
- The device allows quick coupling and uncoupling and provides for articulation.
- A turntable is a load-bearing plate that supports vertical and horizontal loads, and is coupled to the semi-trailer's kingpin and locked into place by a set of jaws.
Turntable/fifth wheel
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- A load carrying trailer that has its axle group towards the rear of the trailer.
- A semi-trailer's forward connection is by means of a kingpin to either a prime-mover, converter dolly or lead semi-trailer. This arrangement allows up to half of the trailer's load to be carried by the prime-mover/convertor dolly/lead semi-trailer.
Semi-trailer Road train with two (2) semi-trailers and one (1) converter dolly
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- A short trailer with its forward connection by a drawbar. The drawbar normally pivots vertically.
- Dollys are only equipped with a turntable.
- Dollys are designed to carry some of the load of an attached semi-trailer rather than a load itself.
- Road trains are an example of where a converter dolly is used as part of the combination.
Converter dolly
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- A load carrying trailer that has an axle group near its centre.
- Forward connection is by a drawbar, which is normally rigid.
Pig trailer Rigid truck and pig trailer combination
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- A combination consisting of a fixed or converter dolly attached to a semi-trailer.
Dog trailer Triple road train with 2 dog trailers
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- A prime-mover towing two semi-trailers.
- The first trailer is a lead semi-trailer (A trailer), the second is a conventional semi-trailer (B trailer).
- The lead semi-trailer (A trailer) has a turntable at its rear, which means another semi-trailer can connect without the use of a converter dolly.
- B-triple are variations of this concept where three semi-trailers are connected.
Lead semi trailer B-double
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- A haul unit designed to tow other vehicles by means of a drawbar (rather than using a turntable).
- They are often used to tow platforms, or a dog trailer, in situations where road trains are required to break up (split) at assembly areas.
Block truck
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13. What is a trailer drawbar and it's length requirements?
- Can be either a single rigid bar or an a-frame which is part of a trailer (except a semi-trailer) connecting the trailer body to a coupling for towing purposes.
- The distance between the coupling pivot point on the drawbar of a dog trailer, and the centre of the front axle group or of the front single axle of the trailer, must not be:
- over 5 metres; and
- under 3 metres, if the trailer is used in a road train over 19m long.
- The distance between the coupling pivot point on a drawbar, and the centre of the axle group or single axle on a trailer with only one axle group or single axle (except a semi-trailer), must not be over 8.5 metres.
Drawbar
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Heavy Vehicle Operations
- Phone: (08) 9311 8450
- E-mail: hvo@mainroads.wa.gov.au
- Fax: (08) 9311 8455