139Air brakes of motor vehicles in B‑doubles or road trains

139 Air brakes of motor vehicles in B‑doubles or road trains

(1) If a B‑double or road train is fitted with brakes that operate using compressed air, the braking system of the motor vehicle must comply with subrules (2) and (3) when: (a) the pressure is measured in an 800 millilitre vessel connected by a 2 metre pipe with a bore of approximately 13 millimetres to the coupling head of the braking system; and (b) the air pressure before the brakes are applied is not under: (i) the average of the maximum and minimum pressures in the operating pressure range specified by the vehicle’s manufacturer; or (ii) if there is no manufacturer’s specification—650 kilopascals. (2) The pressure must reach at least 420 kilopascals within 400 milliseconds after the rapid and complete application of the foot‑operated brake control. (3) After the brakes have been fully applied, the pressure must fall, within half a second after the release of the foot‑operated brake control, to 35 kilopascals.