Elevated railway

An elevated railway or elevated train (also known as an el train or el for short) is a railway with the tracks above street level on a viaduct or other elevated structure (usually constructed from steel, cast iron, concrete, or bricks). The railway may be a broad-gauge, standard-gauge or narrow-gauge railway, light rail, monorail, or a suspension railway. Elevated railways are normally found in urban areas where there would otherwise be multiple level crossings. Usually, the tracks of elevated railways that run on steel viaducts can be seen from street level.
The earliest elevated railway was the London and Greenwich Railway on a brick viaduct of 878 arches, built between 1836 and 1838. The first 2.5 miles (4.0 km) of the London and Blackwall Railway (1840) was also built on a viaduct. During the 1840s there were other plans for elevated railways in London that never came to fruition.
From the late 1860s onward, elevated railways became popular in US cities. New York's West Side and Yonkers Patent Railway opened in 1868 as a cable-hauled elevated railway and was operated using locomotives after 1871, when it was renamed the New York Elevated Railroad. This was followed in 1875 by the Manhattan Railway Company, which took over the New York Elevated Railroad. Other early elevated systems in the US included the Chicago "L", which was built by multiple competing companies beginning in 1892, as well as the Boston Elevated Railway in 1901 and the Market–Frankford Line in Philadelphia in 1907. Globally, the Berlin Stadtbahn (1882) and the Vienna Stadtbahn (1898) are also mainly elevated.
The first electric elevated railway was the Liverpool Overhead Railway, which operated through Liverpool docks from 1893 until 1956.
In London, the Docklands Light Railway is a modern elevated railway that opened in 1987 and has since expanded. The trains are driverless and automatic. Another modern elevated railway is Tokyo's driverless Yurikamome line, opened in 1995.
Most monorails are elevated railways, such as the Disneyland Monorail System (1959), the Tokyo Monorail (1964), the Sydney Monorail (1988–2013), the KL Monorail, the Las Vegas Monorail, the Seattle Center Monorail and the São Paulo Monorail. Most maglev railways are also elevated.
During the 1890s there was some interest in suspension railways, particularly in Germany, with the Schwebebahn Dresden, (1891–) and the Wuppertal Schwebebahn (1901). H-Bahn suspension railways were built in Dortmund and Düsseldorf airport, 1975. The Memphis Suspension Railway opened in 1982.
Suspension railways are usually monorail; Shonan Monorail and Chiba Urban Monorail in Japan, despite their names, are suspension railways.
People mover or automated people mover (APM) is a type of driverless grade-separated, mass-transit system. The term is generally used only to describe systems that serve as loops or feeder systems, but is sometimes applied to considerably more complex automated systems. Similar to monorails, Bombardier Innovia APM technology uses only one rail to guide the vehicle along the guideway. APMs are common at airports and effective at helping passengers quickly reach their gates. Several elevated APM systems at airports including the PHX Sky Train at Phoenix Sky Harbor International Airport; AeroTrain at Kuala Lumpur International Airport; and the Tracked Shuttle System at London Gatwick Airport, United Kingdom.