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.