Western Australian Current Regulations Western Australian Current Regulations In testing a fifth
wheel coupling built for a 75 mm kingpin used in a B‑double or road
train to decide whether its D‑value complies with
regulation 369(1), the longitudinal movement (after readjusting the jaws
of the coupling using a kingpin built to the dimensions mentioned in
regulation 373(3)(a)) must not be over 4 mm.