It is important to be able to forecast the performance of the subgrade, especially its acceptable limits of deformation derived for both the construction stage and during the working life of the pavement. Ten types of in situ test apparatus are described briefly and comparisons made between them, setting out their usefulness, field of application and limitations. Three studies comparing in situ tests are identified and described. The tests using large platens gave reasonably consistent results and comparable with the instrumented measurements such that reasonable confidence can be placed in the stiffnesses derived from their output. Seventeen PIARC member countries contributed information about their methods of subgrade assessment which was in response to a questionnaire seeking information on site investigation, design, construction and maintenance stages.