For over 50 years, the structural condition of a conventionnal pavements has been characterized by the bearing capacity, measured through the deflection produced by a rolling or impact load. However, modern pavements exhibit specific defects which have small or even no effect on deflection. To overcome this difficulty, two types of dynamic survey methods have been developed, the so-called “dispersive methods”, and the “impedance method”. The first group involves single-, two- and multi-station dispersive methods. Theoretical and experimental studies show that, although the multi-station dispersion method seems the most powerful! one, it requires considerable resources, and thus it is, today, inadequate for routine analysis of pavements. The two-station method provides, when pavement layers are correctly bonded, a simple but promising approach for determining the mechanical parameters of the pavements. The impedance method, which was recently developed by the french “Laboratoires des Ponts et Chaussées (LPCs)”, provides a reliable means to assess the state of pavements interlayers, and thus complete the two-station dispersive method. Therefore, the LPCs developed a new piece of equipement, the COLIBRI system, which applies both methods on a routine basis.