The paper describes the research into the development of performance testing for foundation layers based on case studies performed by Scott Wilson Pavement Engineering (SWPE). The performance testing was carried out by Falling Weight Deflectometer (FWD), German Dynamic Plate (gdp) AND Prima 100. The results using these test methods were compared and correlated. The results indicated that the relationship between FWD, GDP and Prima were material type and thickness dependent. The Prima usually gave broadly similar results to the FWD, but was significantly more variable from point to point. The GDP almost always gave a lower stiffness than the other devices, but to varying degrees