General Information os rails

Rail transport is an energy-efficient and capital-intensive means of mechanised land transport and is a component of logistics. Along with various engineered components, rails constitute a large part of the permanent way. They provide smooth and hard surfaces on which the wheels of the train can roll with a minimum of friction. As an example, a typical modern wagon can hold up to 125 tons of freight on two four-wheel bogies/trucks (100 tons in UK). The contact area between each wheel and the rail is tiny, a strip no more than a few millimetres wide, which minimizes friction. In addition, the track distributes the weight of the train evenly, allowing significantly greater loads per axle / wheel than in road transport, leading to less wear and tear on the permanent way. This can save energy compared with other forms of transportation, such as road transport, which depends on the friction between rubber tires and the road. Trains also have a small frontal area in relation to the load they are carrying, which cuts down on forward air resistance and thus energy usage, although this does not necessarily reduce the effects of side winds.

Due to these various benefits, rail transport is a major form of public transport in many countries. In Asia, for example, many millions use trains as regular transport in India, China, South Korea and Japan. It is also widespread in European countries. By comparison, intercity rail transport in the United States is relatively scarce outside the Northeast Corridor, although a number of major U.S. cities have heavily-used, local rail-based passenger transport systems or light rail or commuter rail operations.

The vehicles travelling on the rails, collectively known as rolling stock, are arranged in a linked series of vehicles called a train, which can include a locomotive if the vehicles are not individually powered. A locomotive (or "engine") is a powered vehicle used to haul a train of unpowered vehicles. In the USA, individual unpowered vehicles are known generically as cars. These may be passenger carrying or used for freight purposes. For passenger-carrying vehicles, the term carriage or coach is used, while a freight-carrying vehicle is known as a freight car in the United States and a wagon or truck in Great Britain. An individually-powered passenger vehicle is known as a railcar or a power car; when one or more as these are coupled to one or more unpowered trailer cars as an inseparable unit, this is called a railcar set or multiple unit.