This European Standard specifies a direct method for characterizing the surface roughness of the rail and wheel associated with rolling noise (??acoustic roughness??)@ in the form of a one-third octave band spectrum. This standard describes a method for: a) selecting measuring positions along a track or selecting wheels of a vehicle; b) selecting lateral positions for measurements; c) the data acquisition procedure; d) measurement data processing in order to estimate a set of one-third octave band roughness spectra; e) presentation of this estimate for comparison with limits of acoustic roughness; f) comparison with a given upper limit in terms of a one-third octave band wavelength spectrum; g) the measuring system requirements. It is applicable to the: a) performance testing of reference track sections in relation to the acceptance test for noise emitted by railway vehicles; b) performance testing of track sections in relation to noise emitted by railway vehicles; c) acceptance of the running surface condition only in the case where the acoustic roughness is the acceptance criterion; d) assessment of the wheel surface condition as an input for the acoustic acceptance of brake blocks; e) assessment of the wheel and rail roughness as input to the calculation of combined wheel rail roughness; f) diagnosis of wheel-rail noise issues for specific tracks or wheels; g) assessment of the wheel and rail roughness as input to rolling noise modelling; h) assessment of the wheel and rail roughness as input to noise source separation methods. It is not applicable to the: a) measurement of roughness (rail roughness@ wheel roughness or combined roughness) using an indirect method; b) analysis of the effect of wheel-rail interaction@ such as a ??contact filter??; c) approval of rail and wheel reprofiling@ including rail grinding operations@ except for those where the acoustic roughness is specifically the approval criterion (and not the grinding quality criteria as provided in e.g. EN 13231-3); d) characterization of track and wheel geometry except where associated with noise generation.