The original medieval structure was a five-span structure with three river arches built of voussoirs and smaller flood arches on each bank (the water covered them only during the raised level of the river). Sterlings had straight, pointed shapes. The two visible arches span 13.7 meters on the western side and 6.9 meters on the eastern side of the bridge.
Salter M., Medieval Bridges, Malvern 2015.
Website wikipedia.org, Old Bridge, Bridgend.