Bridges are classified into five categories based on their structure and architecture. A distinction is, therefore, made between vaulted bridges whose deck rests on several pillars like the one visible in this photo, arch bridges with a single arch, beam bridges, suspension bridges, and cable-stayed bridges. The line of the lower part - also called intrados - of the vaulted bridges can take different arch shapes. The semicircular arch made up of a complete semicircle of this Norman bridge is the most frequently encountered type of vault. It is actually present in about 67% of the masonry railway bridges of the French network and was almost exclusively used by the Romans.