This Technical Specification describes the methods that are available to perform a spectral analysis of pavement surface profile signals. It specifies three possible methods for spatial frequency analysis (or texture wavelength analysis) of two-dimensional surface profiles that describe the pavement roughness amplitude as a function of the distance along a straight or curved trajectory over the pavement. The result of the frequency analysis will be a spatial frequency (or texture wavelength) spectrum in constant-percentage bandwidth bands of octave or one-third-octave bandwidth. This Technical Specification offers three alternative methods to obtain these spectra: 1) analogue constant-percentage bandwidth filtering; 2) digital constant-percentage bandwidth filtering; 3) constant narrow bandwidth frequency analysis by means of Discrete Fourier Transform, followed by a transformation of the narrow-band spectrum to an octave- or one-third-octave-band spectrum. The objective of this Technical Specification is to standardize the spectral characterization of pavement surface profiles. This objective is pursued by providing a detailed description of the analysis methods and related requirements for those who are involved in pavement characterization, but are not familiar with general principles of frequency analysis of random signals. These methods and requirements are generally applicable to all types of random signals, but are elaborated in this Technical Specification in a specific description aimed at their use for pavement surface profile signals. NOTE The user of this Technical Specification should be aware that spectral analysis as specified in this document cannot express all characteristics of the surface profile under study. In particular, the effects of asymmetry of the profile, e.g. the difference of certain functional qualities for “positive” and “negative” profiles cannot be expressed by the power spectral density, as it disregards any asymmetry of the signal. (See Annex F.)