The basis of a new non-destructive method for concrete pavements is described. The method uses a hybrid approach that combines frequency domain (impact-echo) and time domain (seismic) data. The equipment and data interpretation for the hybrid approach are described. The dynamic response data are interpreted in terms of guided plate wave (Lamb wave) theory, which are shown to follow the S1 Lamb mode behavior. The developed field testing procedure is then described. Results from verification tests, carried out on full-scale concrete slabs, show that the new method provides accurate thickness estimates. On average the error between predicted thickness and actual thickness determined by cores is less than 6mm, although some individual estimates exceed this error value.