This paper deals with the influence of a bituminous mix surfacing on orthotropic deck bridges. These researches are part of a French national project “Orthoplus,” which is briefly introduced. The approach to take into account the surfacing and to develop calculation tools is explained. First, the behavior of the different bituminous constituent materials is investigated. A linear viscoelastic modeling is proposed with a rheological model, previously developed at the Civil Engineering and Buildings Dept. (“DGCB”) of the University of Lyon/ENTPE. This model is implemented in a Finite Elements code, which enables the simulation of any orthotropic structures. To validate the proposed numerical tool, the highest bridge in the world, the Millau Viaduct (France) is studied. In situ measurements were especially carried out on the Millau Viaduct. Focus is made on comparisons between experimental data and simulations results. Influence of vehicle speed on bridge response is also analyzed.