This International Standard specifies tests for determining the steady-state directional control response of heavy vehicles, one of the factors composing vehicle dynamics and road-holding properties. It is applicable to heavy vehicles, i.e. commercial vehicles, 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.