A train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and transport people or freight. Trains are typically pulled or pushed by locomotives (often known simply as "engines"), though some are self-propelled, such as multiple units or railcars. Passengers and cargo are carried in railroad cars, also known as wagons or carriages. Trains are designed to a certain gauge, or distance between rails. Most trains operate on steel tracks with steel wheels, the low friction of which makes them more efficient than other forms of transport. Many countries use rail transport.
Trains have their roots in wagonways, which used railway tracks and were powered by horses or pulled by cables. Following the invention of the steam locomotive in the United Kingdom in 1802, trains rapidly spread around the world, allowing freight and passengers to travel over land faster and more cheaply than ever before. Rapid transit and tram systems were first built in the late 1800s to transport large numbers of people in and around cities. Beginning in the 1920s, and accelerating following World War II, diesel and electric locomotives replaced steam as the means of motive power. Following the development of cars, trucks, and extensive networks of highways which offered greater mobility, as well as faster airplanes, trains declined in importance and market share, and many rail lines were abandoned. The spread of buses led to the closure of many rapid transit and tram systems during this time as well.
Since the 1970s, governments, environmentalists, and train advocates have promoted increased use of trains due to their greater fuel efficiency and lower greenhouse gas emissions compared to other modes of land transport. High-speed rail, first built in the 1960s, has proven competitive with cars and planes for short- to medium-distance travel. Commuter rail has grown in importance since the 1970s as an alternative to congested highways and a means to promote development, as has light rail in the 21st century. Freight trains remain important for the transport of bulk commodities such as coal and grain, as well as for reducing road traffic congestion caused by freight trucks.
While conventional trains operate on relatively flat tracks with two rails, many specialized trains operate in significantly different ways. Monorails operate on a single rail, while funiculars and rack railways are uniquely designed to traverse steep slopes. Experimental trains such as high-speed maglevs, which use magnetic levitation to float above a guideway, have been under development since the 1970s and can reach speeds higher than even the fastest conventional trains. Trains that use alternative fuels such as natural gas and hydrogen are a 21st-century development.
Types and terminology
Trains can be sorted into types based on whether they haul passengers or freight (though mixed trains which haul both exist), by their weight (heavy rail for regular trains, light rail for lighter transit systems), by their speed (low speed and high speed), by their distance (short haul, long distance, transcontinental), and by what form of track they use. Conventional trains operate on two rails, but several other types of track systems are also in use around the world, such as monorail.
Terminology The railway terminology that is used to describe a train varies between countries. The International Union of Railways seeks to provide standardized terminology across languages. The Association of American Railroads provides terminology for North America. Terms include:
Train (Britain): a light locomotive, self-propelled rail vehicle or road–rail vehicle in rail mode. Train (United States): a connected line of railroad cars with or without a locomotive. Rolling stock (many jurisdictions): any railway vehicle. Rake (Britain): a collection of passenger or freight vehicles connected (not necessarily with a locomotive). Consist (North America and Australia): a train, locomotive(s), cut of cars, or any single car not coupled to another car or locomotive. Trainset (many jurisdictions): a set of vehicles that are permanently coupled together (such as the TGV, ICE or Pioneer Zephyr).
History
Early history
Trains are an evolution of wheeled wagons running on stone wagonways, the earliest of which were built by Babylon circa 2,200 BCE. Starting in the 1500s, wagonways were introduced to haul material from mines; from the 1790s, stronger iron rails were introduced. Following early developments in the second half of the 1700s, in 1804 a steam locomotive built by British inventor Richard Trevithick powered the first ever steam train. Outside of coal mines, where fuel was readily available, steam locomotives remained untried until the opening of the Stockton and Darlington Railway in 1825. British engineer George Stephenson ran a steam locomotive named Locomotion No. 1 on this long line, hauling over 400 passengers at up to . The success of this locomotive and Stephenson's Rocket in 1829 convinced many of the value of steam locomotives, and within a decade, the stock market bubble known as "Railway Mania" spread across the United Kingdom.
News of the success of steam locomotives quickly reached the United States, where the first steam railroad opened in 1829. Railroad pioneers in the United States soon started manufacturing their own locomotives, designed to handle the sharper curves and rougher track typical of the country's railroads. The other nations of Europe also took note of British railroad developments, and most countries on the continent constructed and opened their first railroads in the 1830s and 1840s, following the first run of a steam train in France in late 1829. In the 1850s, trains continued to expand across Europe, with many influenced by or purchases of locomotive designs from the United States. Other European countries pursued their own distinct designs. Around the world, steam locomotives grew larger and more powerful throughout the rest of the century as technology advanced.
Trains first entered service in South America, Africa, and Asia through construction by imperial powers, which starting in the 1840s built railroads to solidify control of their colonies and transport cargo for export. In Japan, which was never colonized, railroads first arrived in the early 1870s. By 1900, railroads were operating on every continent besides uninhabited Antarctica.
New technologies
Even as steam locomotive technology continued to improve, inventors in Germany began developing alternative methods for powering trains. Werner von Siemens built the first train powered by electricity in 1879, and went on to pioneer electric trams. Another German inventor, Rudolf Diesel, constructed the first diesel engine in the 1890s, though the potential of his invention to power trains was not realized until decades later. Between 1897 and 1903, tests of experimental electric locomotives on the Royal Prussian Military Railway in Germany demonstrated they were viable, setting speed records in excess of .Early gas powered "doodlebug" self-propelled railcars entered service on railroads in the first decade of the 1900s. Experimentation with diesel and gas power continued, culminating in the German "Flying Hamburger" in 1933, and the influential American EMD FT in 1939. These successful diesel locomotives showed that diesel power was superior to steam, due to lower costs, ease of maintenance, and better reliability. Meanwhile, Italy developed an extensive network of electric trains during the first decades of the 20th century, driven by that country's lack of significant coal reserves.
Dieselization and increased competition World War II caused widespread destruction of existing railroads across Europe, Asia, and Africa. Following the war's conclusion in 1945, nations which had suffered extensive damage to their railroad networks took the opportunity provided by Marshall Plan funds (or economic assistance from the USSR and Comecon, for nations behind the Iron Curtain) and advances in technology to convert their trains to diesel or electric power. France, Russia, Switzerland, and Japan were leaders in adopting widespread electrified railroads, while other nations focused primarily on dieselization. By 1980, the majority of the world's steam locomotives had been retired, though they continued to be used in parts of Africa and Asia, along with a few holdouts in Europe and South America. China was the last country to dieselize fully, due to its abundant coal reserves; steam locomotives were used to haul mainline trains as late as 2005 in Inner Mongolia.
Trains began to face strong competition from automobiles and freight trucks in the 1930s, and this competition intensified greatly following World War II. After the war, air transport also became a significant competitor for passenger trains. Large amounts of traffic shifted to these new forms of transportation, resulting in a widespread decline in train service, both freight and passenger. A new development in the 1960s was high-speed rail, which runs on dedicated rights of way and travels at speeds of or greater. The first high-speed rail service was the Japanese Shinkansen, which entered service in 1964. In the following decades, high-speed rail networks were developed across much of Europe and Eastern Asia, providing fast and reliable service competitive with automobiles and airplanes. The first high-speed train in the Americas was Amtrak's Acela in the United States, which entered service in 2000.
To the present day Towards the end of the 20th century, increased awareness of the benefits of trains for transport led to a revival in their use and importance. Freight trains are significantly more efficient than trucks and emit far fewer greenhouse gas emissions per ton-mile; passenger trains are also far more energy-efficient than other modes of transport. According to the International Energy Agency, "On average, rail requires 12 times less energy and emits 7–11 times less GHGs per passenger-km traveled than private vehicles and airplanes, making it the most efficient mode of motorized passenger transport. Aside from shipping, freight rail is the most energy-efficient and least carbon-intensive way to transport goods." As such, rail transport is considered an important part of achieving sustainable energy. Intermodal freight trains, carrying double-stack shipping containers, have since the 1970s generated significant business for railroads and gained market share from trucks. Increased use of commuter rail has also been promoted as a means of fighting traffic congestion on highways in urban areas.
Components
Bogies
Bogies, also known in North America as trucks, support the wheels and axles of trains. Trucks range from just one axle to as many as four or more. Two-axle bogies are the most common worldwide, as they decrease the impact of track irregularities, improve curve negotiation, and distribute heavy loads more effectively than single-axle bogies.
Couplers
Train vehicles are linked to one another by various coupling systems. In much of Europe, India, and South America, trains primarily use buffers and chain couplers. In the rest of the world, knuckle couplers are the most popular, with a few local variations persisting (such as Wilson couplers in the former Soviet Union). On multiple units all over the world, Scharfenberg couplers are common.
Brakes