This International Standard specifies open-loop test methods for determining the effect of braking on the course-holding and directional behaviour of heavy vehicles or heavy vehicle combinations when braking is accomplished using — the service-brake system, or — the retarder or engine brake only. This International Standard is applicable to heavy vehicles — i.e. commercial vehicles, commercial vehicle combinations, buses and articulated buses as defined in ISO 3833 — covered by Categories M3, N2, N3, O3 and O4 of UNECE (United Nations Economic Commission for Europe) and EC vehicle regulations. These categories pertain to trucks and trailers with a maximum mass above 3,5 t and to buses and articulated buses with a maximum mass above 5 t.