Thomas Telford's cast-iron bridges

Thomas Telford's innovations using cast iron included a landmark lightweight type of arch bridge with spans of 32–52 m, longer than then practicable in stone and exhibiting an unparalleled combination of strength, economy and intuitive design. This development influenced cast-iron bridge building until the 1830s and the adoption of elegant and effective lozenge-lattice bracing in bridge spandrels until the 1870s. This paper identifies and examines Telford's mastery in cast-iron bridge design, exemplified by a legacy of six bridges which are still operational in varying degrees after nearly two centuries.