Abstract: A structure for supporting a road along a road axis over an underpass space spanned by the structure. The structure includes two footings underlying the road with each support assembly being securely mounted to the earth. The structure also includes an arcuate support assembly supported by the footings. The support assembly extends at least the width of the road and traverses the underpass space for supporting the road across the underpass space spanned by the structure. The support assembly includes a substantially continuous inner shell, a plurality of spatially disposed, rigid, resilient beams supported by the footings, an insulating material disposed in the cavities formed in between the rigid, resilient beams, and an outer shell encasing the rigid, resilient beams and the insulating material. A substantially fluid impermeable material substantially encases the support assembly and a fill material extends from the substantially fluid impermeable material to support the road.