Critical transport infrastructure such as roads and railways are costly to construct, thus finding optimized safe solutions is always one of the prioritized tasks for geotechnical engineers. In Norway, the geological conditions are challenging with undulating terrain and widespread soft (frequently quick) clay dominated in many urban populated areas. In planning and design of large transport project, full-scale field testing is often used to test and optimizing geotechnical methods, hypotheses, and solutions in these challenging geological conditions Full-scale field testing is crucial before introducing, for example, a new method or an innovative design in the built environment. Over the years, the Norwegian Geotechnical Institute has conducted various field tests in connection with large road and railway projects. This paper discusses the importance of full-scale field test and presents briefly the experiences from the combined construction project (FRE16) between Ringeriksbanen national railway line and European Route 16 (E16) and from the European Road Project E6 Kvithammar-Åsen.