Western Australian Current Regulations Western Australian Current Regulations (1) Brake line
couplings on the same part of a vehicle in a B‑double or road train must
not be interchangeable.
(2) The couplings must
be polarised in accordance with AS D8‑1971 Hose Couplings for
Use with Vacuum and Air‑Pressure Braking Systems on Prime Movers,
Trailers and Semi‑trailers if the hoses used with the brake couplings
are used for the same purpose as the hoses mentioned in the standard.