This study revisits pavement roughness and examines the suitability of the International Roughness Index (IRI) to describe passenger car ride quality, as well as heavy vehicle excitation and dynamic loads. It describes the development of a new pavement roughness index, called RIDE (Roughness Index for Driving Expenditure). RIDE is based on sprung mass acceleration, rather than relative axle displacement like the IRI. RlDE is calculated in the frequency domain on the basis of the transfer function of a reference vehicle. It results in the root-mean-square (RMS) acceleration of the sprung mass per unit length of pavement traveled. This index is compatible to the current ISO and it is also related to heavy vehicle dynamic excitation.