1. B-double
B-double means a combination consisting of a prime mover towing 2 semitrailers, with 1 semitrailer supported at the front by, and connected to, the other semitrailer.
2. Road train
Road train means a combination (other than a B-double) either using a rigid truck hauling unit towing at least one trailer of which the combination length is greater than 19m or a prime mover hauling unit towing at least two trailers and includes a vehicle categorised as a B- triple, AB-triple, BAB-quad, or ABB-quad. (a converter dolly supporting a semitrailer is counted as one trailer).
Type 1
Road train means a road train using either a rigid truck hauling unit towing one trailer when the combination length is not longer than 31.5m or for a road train using a prime mover hauling unit towing two trailers when the combination length is not longer than 36.5m. B-triple and AB-triple combinations up to 36.5m are categorised as a Type 1 road train.
Type 2
Road train” means a road train using either a rigid truck hauling unit towing two trailers when the combination length is not longer than 47.5m or a road train using a prime mover hauling unit towing three or four trailers when the combination length is not longer than 53.5m. AB-triple combinations longer than 36.5m and up to a length of 44.0m are categorised as a Type 2 road train. Maximum lengths of road train.
Vehicle combinations
Max length (metres)
Vehicle category
A rigid truck towing one trailer (total length exceeding 19 m) 31.5
Type 1
A prime mover towing two semitrailers connected by a drawbar 36.5
Type 1
B-triple: A prime mover towing 3 semitrailers connected by turntable couplings 36.5
Type 1
AB-triple: A prime mover towing a single semitrailer and a set of B-double trailers, connected by a converter dolly 36.5
Type 1 Longer AB-triple: 44.0
Type 2
A rigid truck towing two semitrailers connected by a drawbar 47.5
Type 2
BAB-quad: A prime mover towing two sets of B-double trailers, connected by a converter dolly 53.5
Type 2
ABB-quad: A prime mover towing a single semitrailer and a set of B- triple trailers, connected by a converter dolly 53.5
Type 2
A prime mover towing three semitrailers connected by drawbars 53.5
Type 2