Elevated railway

An elevated railway (also known in Europe as overhead railway) is a rapid transit railway with the tracks above street level on a viaduct or other steel, concrete or brick structure. The railway may be standard gauge, narrow gauge, light rail, monorail or a suspension railway. Elevated railways are usually used in urban areas where there would otherwise be a large number of level crossings. Most of the time, the tracks of elevated railways that run on steel viaducts can be seen from street level.

History

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 on a viaduct. During the 1840s there were other schemes for elevated railways in London which did not come to fruition.

From the late 1860s elevated railways became popular in US cities. The New York West Side and Yonkers Patent Railway operated with cable cars from 1868 to 1870, thereafter locomotive-hauled. This was followed by the Manhattan Railway in 1875, the Boston Elevated Railway (1887–), and the South Side Elevated Railroad, Chicago (1892–). The Chicago transit system itself is known as "L", short for "elevated". The Berlin Stadtbahn (1882) is also mainly elevated.

Rapid transit

Rapid transit, also known as metro, subway or underground is a type of high-capacity public transport generally found in urban areas. Unlike buses or trams, rapid transit systems are electric railways that operate on an exclusive right-of-way, which cannot be accessed by pedestrians or other vehicles of any sort, and which is often grade separated in tunnels or on elevated railways.

Modern services on rapid transit systems are provided on designated lines between stations typically using electric multiple units on rail tracks, although some systems use guided rubber tyres, magnetic levitation, or monorail. The stations typically have high platforms, without steps inside the trains, requiring custom-made trains in order to avoid gaps. They are typically integrated with other public transport and often operated by the same public transport authorities. However, some rapid transit systems have at-grade intersections between a rapid transit line and a road or between two rapid transit lines. It is unchallenged in its ability to transport large numbers of people quickly over short distances with little use of land. Variations of rapid transit include people movers, small-scale light metro, and the commuter rail hybrid S-Bahn.