In anticipation of the introduction of high modulus materials in the Swiss standards, a research project has been carried out for the evaluation of these bituminous mixtures. These mixtures make possible to reduce rut in base courses. With a temperature of 50°C, three test sections (two with high modulus and one with a reference material for base layer), were built in a building for ALT and were submitted to traffic loads corresponding to those of heavy vehicles. The behaviour of the test sections corresponds to the results provided by laboratory test made with LCPC rutting tests. The section designed to have a strong rut resistance has no rut in the base layer. The two others sections present important permanent deformation, even the one using hard bitumen (in this last case, the mixture was mainly designed to have high fatigue resistance). A second experience shows that rutting increases strongly with addition of transverse loads.