Locomotive

A locomotive also known as an engine, is a type of rail transport vehicle with the purpose of providing the main moving power for a train. Many locomotives today are capable of multiple working, meaning more than one can be on a train, sharing power and be controlled by a single operator. The way in which a locomotive is able to push or pull a train determines the type of locomotive.

## Types of Locomotives

### Steam

Steam Locomotives work, by heating water in a boiler causing it to evaporate into steam, and then using the steam to propel a piston(s), which then turns the wheels. This type of locomotive was the first type to be developed and was in widespread usage until the mid-1950s in the Eastern United States. Today, while they are still sometimes used for excursion trips, they are not used in regularly-scheduled passenger service.

### Diesel

A diesel locomotive, is a type of locomotive in which the prime mover runs using a diesel fuel-powered engine. Several types of diesel locomotives have been designed, developed, and used with the main variations occurring in how mechanical power is used to turn the wheels of the locomotive. The most common transmission type of diesel locomotive, frequently used around the world is the diesel-electric locomotive. In this type of diesel locomotive, diesel fuel is directly used as the power source for an electrical generator. The generator then uses the electricity produced to turn the wheels of the locomotive, thus making the locomotive technically diesel and electric powered.

Diesel locomotives are almost always exclusively used on areas of track that lack electrification in the Northeastern United States, however it is not uncommon to see diesel engines running on electrified lines that soon later on, have a termination point of electrification. One of the main drawbacks to operating diesel locomotives, are the emissions bans sometimes put into place on them. Busy rail stations, that are usually underground or run through long tunnels, usually prohibit such locomotives, with some examples being Penn and Grand Central Stations both being located in New York City. While they may have more freedom of location usage, they often lack the top-speeds and efficiency of many electric locomotives.

### Electric

Electric locomotives work similarly to diesel-electric locomotives, in the sense that they use an electrical generator that generates electricity, which then turns the wheels, but the power source for the generator is instead derived directly from an electrical power source. The type of electrical power source varies but the two most-common and only in the northeast are overhead catenary- where wires lie directly above the train providing it with electricity or third-rail where a third rail either to the right or left sides of the two wheel-rails, makes contact with a part of the train and provides it with electricity.

Electric locomotives are generally confined to the Northeast United States, where many lines have catenary or third-rail, although there are a hand full of lines outside the Northeast that do operate with electricity. However, because of their efficiency and high top speeds, many railroads are working on incorporating a source of electricity onto their rail lines. On many busy routes such as the Northeast Corridor, the Philadelphia to Harrisburg section of the Keystone Corridor, and many other frequently used commuter rail lines, it is usually common to see electrification of the route in question. Although electric locomotives have great benefits over diesel and steam, they are severely hampered in the event that there is a power source disruption.

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