Mediæval bridges were constructed from the local stone (granite or slate) in one or more pointed or rounded arches spanning a river, with two low parapet walls either side of the carriageway, topped off with coping stones. The bridges are often quite narrow and the parapets may be offset to provide refuges to allow pedestrians to avoid wheeled traffic. The bridge piers were often set onto triangular ‘cutwaters’ which deflected the flow of the water.