The use of expanded polystyrene (EPS) geofoam instead of traditional "heavy" sand for pavement subbases can reduce or even eliminate the additional load on the subsoil, thus decreasing or eliminating the settlement of pavement structures on a compressible subsoil. Experience with EPS geofoam is very positive, but a uniform design procedure does not yet exist for this type of structure. Optimization of the existing EPS pavement design guidelines and their improvement has demanded materials research on EPS, the use of three-dimensional finite-element pavement models, and in situ full-scale measurement. Extensive materials research provided data for the stress-strain response of EPS under representative loading and environmental conditions. Three-dimensional modeling enabled critical evaluation of existing design methodologies by analyzing pavements with different road bases, different EPS types, and different asphalt thicknesses. In situ measurements by means of built-in strain transducers in asphalt provided data for verification of the three-dimensional modeling. Furthermore, evaluation and monitoring of Dutch projects with EPS geofoam were carried out to define problematic aspects from the practical point of view. On the basis of the research findings, the current Dutch design guidelines have been revised and optimized. In order to make this knowledge easily accessible, an official Dutch design manual for lightweight pavements with EPS geofoam was published under the auspices of the Center for Research and Contract Standardization in Civil and Traffic Engineering. An outline of the manual is presented.