Arches have proven to be efficient load bearing structures for centuries. Today structural designers utilize long-span arches to support bridges for their stability, efficiency, high load capacity and their architectural and urban form-making potential. The efficiency of the arch structure is strongly related to its shape: it is difficult to find another type of structure where the connection between geometry and internal loading is so pronounced. The selection of the best arch geometry is key in reducing the structural volume because a good arch shape allows for the predominance of axial internal actions with low or no eccentricity under a wide range of loading combinations.