Rail transport

Rail transport is the conveyance of passengers and goods by means of wheeled vehicles specially designed to run along railways or railroads. Rail transport is part of the logistics chain, which facilitates international trade and economic growth in most countries.

Typical railway tracks consist of two parallel rails, normally made of steel, secured to crossbeams, termed sleepers (UK and Australia) or ties (US). The sleepers maintain a constant distance between the two rails; a measurement known as the "gauge" of the track. To maintain the alignment of the track it is either laid on a bed of ballast or else secured to a solid concrete foundation. The whole is referred to as permanent way (UK and Australia usage) or right-of-way (North American usage).

Railway rolling stock, which is fitted with metal wheels, moves with low frictional resistance when compared to road vehicles. On the other hand, locomotives and powered cars normally rely on the point of contact of the wheel with the rail for traction and adhesion (the part of the transmitted axle load that makes the wheel "adhere" to the smooth rail). While this is usually sufficient under normal dry rail conditions, adhesion can be reduced or even lost through the presence of unwanted material on the rail surface, such as moisture, grease, ice, or dead leaves.

History

Stone rails

The earliest evidence of a railway found thus far was the 6-kilometre (3.7 mi) Diolkos wagonway, which transported boats across the Corinth isthmus in Greece during the 6th century BC. Trucks pushed by slaves ran in grooves in limestone, which provided the track element, preventing the wagons from leaving the intended route. The Diolkos ran for over 1300 years, until 900 AD.[5] The first horse-drawn wagonways also appeared in ancient Greece, with others to be found on Malta and various parts of the Roman Empire, using cut-stone tracks. An example of stone track still exists on Dartmoor, England, where the Haytor Granite Tramway was built in 1820 using grooved granite blocks.


Wooden rails

Railways began reappearing in Europe after the Dark Ages following the collapse of the Roman Empire. The earliest known record of a railway in Europe from this period is a stained-glass window in the Minster of Freiburg im Breisgau dating from around 1350.[6] By 1550, narrow gauge railways operating with wooden rails were common in mines in Europe.[7] The first railways in Great Britain (also known as wagonways) were constructed in the early 17th century, mainly for transporting coal from mines to canal wharfs where it could be transferred to a boat for onward shipment. The earliest recorded examples are the Wollaton Wagonway in Nottinghamshire and the Bourtreehill - Broomlands Wagonway in Irvine, Ayrshire. Other examples can be found in Broseley in Shropshire, where wooden rails and flanged wheels were utilised, as on a modern railway. However, the rails were prone to wear out under the pressure, and had to be replaced regularly.


Iron plate rail

In 1768, the Coalbrookdale Iron Works laid cast iron plates on top of the wooden rails, providing a more durable load-bearing surface. These were later used by Benjamin Outram at his foundry in Ripley, Derbyshire, the first time standardised components were produced. It was these that led to the name "platelayer" for workers on the permanent way. The advantage was that a considerable variation in wheel spacing (gauge) could be accommodated. However, wheels would bind against the upright part of the plate, and mud and stones would accumulate. On the Little Eaton Gangway in 1799, where Outram used passing loops on the single track, moveable plates were provided, called "pointers", which became shortened to "points".[8]


Edge rail

From the late 18th century, iron "edge rails" began to appear. The British civil engineer William Jessop designed smooth iron edge rails, which were used in conjunction with flanged iron wheels, introducing them on a route between Loughborough and Nanpantan, Leicestershire, as an adjunct to the Charnwood Forest Canal, in 1793-4[9]. In 1803, Jessop opened the Surrey Iron Railway in south London, arguably the world's first horse-drawn public railway.[10] Being of cast iron these rails were short, around three feet long, of a "fish-bellied" design. They had a foot at each end by means of which they were fastened to stone blocks in the ground.


Wrought iron and steel

Cast iron is a brittle material and the short lengths meant that they soon became uneven. However, developments in the process of hot rolling iron meant that longer length rails could be produced. In 1805, the first wrought iron rails were produced at Bedlington Ironworks near Durham. The first steel rails were produced by Robert Forester Mushet and laid at Derby station in 1857[9]. Modern railways still use steel rails, but they are typically welded together to form lengths of continuous welded rail; these remove the additional wear and tear on rolling stock caused by the tiny differences in rail surface height at the joint between adjacent rail sections.