One of the key parameters for analytical design or evaluation of a pavement is the stiffness modulus appropriate to each layer. This paper discusses both the laboratory determination of stiffness modulus, by means of the Indirect Tensile Stiffness Modulus (ITSM) test, and in situ determination, by means of the Falling Weight Deflectometer (FWD). Their complimentary roles are highlighted by means of several examples. The role of ITSM testing in allowing proper temperature correction of FWD data is presented. A comparison of laboratory and in situ moduli is seen to provide information on crack severity, material variability and debonding.

Finally, these stiffness modulus tests are set in the context of a full pavement evaluation and their role in providing vital evidence on overall pavement condition is shown.