Western Australian Current Regulations Western Australian Current Regulations (1) The capacity of
the air storage tanks of a motor vehicle used in a B‑double or road
train must be at least 12 times the volume of all the brake activation
chambers on the motor vehicle.
(2) The capacity of
the air storage tanks of a trailer used in a B‑double or road train must
be at least 8 times the volume of all the brake activation chambers on
the trailer.