A realistic road model must take into account the correlation between the different axles and
the correlation between parallel tracks. It is generally agreed that typical road surfaces may be
considered as realizations of homogeneous and isotropic two-dimensional Gaussian random
processes and these assumptions make it possible to completely describe a road profile by a singlepower
spectral density evaluated from any longitudinal track [1,2]. Then, the spectral description
of the road, together with a knowledge of traversal velocity and of the dynamic properties of the
vehicle, provide a response analysis which will describe the response of the vehicle expressed in
terms of displacement, acceleration, or stress [3].