A railway track (British English and UIC terminology) or railroad track (American English), also known as a train track or permanent way, is the structure on a railway or railroad consisting of the , fasteners, railroad ties (sleepers, British English) and ballast (or slab track), plus the underlying subgrade. It enables trains to move by providing a dependable surface for their wheels to roll upon. Early tracks were constructed with wooden or cast iron rails, and wooden or stone sleepers; since the 1870s, rails have almost universally been made from steel. History of the railway track The first railway in Britain was the Wollaton Wagonway, built in 1603 between Wollaton and Strelley in Nottinghamshire. It used wooden rails and was the first of around 50 wooden-railed tramways built over the next 164 years. These early wooden tramways typically used rails of oak or beech, attached to wooden sleepers with iron or wooden nails. Gravel or small stones were packed around the sleepers to hold them in place and provide a walkway for the people or horses that moved wagons along the track. The rails were usually about long and were not joined - instead, adjacent rails were laid on a common sleeper. The straight rails could be angled at these joints to form primitive curved track. The first iron rails laid in Britain were at the Darby Ironworks in Coalbrookdale in 1767. When steam locomotives were introduced, starting in 1804, the track then in use proved too weak to carry the additional weight. Richard Trevithick's pioneering locomotive at Pen-y-darren broke the plateway track and had to be withdrawn. As locomotives became more widespread in the 1810s and 1820s, engineers built rigid track formations, with iron rails mounted on stone sleepers, and cast-iron chairs holding them in place. This proved to be a mistake, and was soon replaced with flexible track structures that allowed a degree of elastic movement as trains passed over them.