This paper depicts the deployment of Ground-Based Interferometer Synthetic Aperture Radars for obtaining displacements and accelerations of El Tajo and Almonte Viaducts during their routine load tests. These Viaducts belong to the Highspeed Railway Network between Madrid and Badajoz, which represents a strategic infrastructure in Spain. Both Viaducts are concrete arches whose size as well as whose height over the reservoir posed a tremendous challenge for obtaining proper field data using traditional devices. The paper shows the gathered experience on the use of this technique for subsequent routine load tests.