General

Rail transport is an energy efficient means of mechanised land transport. The rail tracks provide very smooth and hard surfaces on which the wheels of the train may roll with a minimum of friction. As an example, a typical rail car can hold up to 125 tons of freight with this and the weight of the car on two four-wheel bogies. Fully loaded, the contact between each wheel and the rail is the space of about one U.S. ten-cent piece. This can save energy compared with other forms of transportation, such as road transport which depends on rubber wheels on pavement. Trains also have a small frontal area in relation to the load they are carrying, which cuts down on air resistance and thus energy usage. In all, under the right circumstances, a train needs 50-70% less energy to transport a given tonnage of freight (or given number of passengers), than does road transport. Furthermore, the rails and sleepers distribute 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 right of way.

Rail transport makes highly efficient use of space: a double-tracked rail line can carry more passengers or freight in a given amount of time than a four-laned road.

As a result, rail transport is often the major form of public transport in many countries. In Asia, for example, many millions use trains as regular transport in India, South Korea, Japan, China, and elsewhere.

Commercially, rail transport has had a mixed record. Most rail systems, including urban metro/subway systems, are highly subsidised and have never or rarely been profitable; however, their indirect benefits are often great. For example, despite a well-developed network consisting of four grades of trains and a widespread urban rail network in Seoul and Pusan, Korean National Rail is a nationalized organization that has never come close to having receipts equal costs (see Transportation in South Korea). Similarly, passenger rail in the US and many other countries is dependent on government subsidies. As a result levels of rail transport have in some times and places been reduced in order to save money (see Beeching Axe). Conversely, US freight railways have consolidated and become more efficient in their progress toward profitability. The East Japan Railway Company has taken an innovative and creative marketing stance and have achieved profitability as a result.

Like other forms of public transport, many railways are having to make considerable investment in order to meet new requirements for security in the face of recent terrorism incidents, for instance the Madrid train bombings of 11 March 2004. Securing railways is often more difficult than other modes of transport because stations are designed with easy access and high capacity as their primary goals rather than security; because most trains make many stops, rendering any sort of passenger screening difficult; and because securing the tracks as they run through cities and the countryside is impractical.

Operations

Main article: Rail transport operations

A rail transport system consists of several necessary elements, and should be viewed from a system-wide perspective when planning, constructing and maintaining it. Some locomotives may be wonderfully aesthetic constructions, but they will not work unless they are given an appropriate system on which to run. This system includes infrastructure such as tracks, railroad switches or points, signals, classification yards, etc.

Firstly there is the geography onto which the permanent way is built. Next are the requirements of the system – what was it built for? For carrying cargo, commuters, medium or long-distance travellers? Has that requirement changed over time and left the system to adapt?

As a result of this, what is the type of system? Is it light rail or rapid transit, high-speed or industrial rail? To what gauge is it built? In a broader sense, rail transport includes monorail, rubber-tyred metros and maglev, since the cars also run in a guided path. (The term "guideway" describes the non-traditional modes better.)

Trains require a propulsion mechanism: horses, or steam, diesel or electric locomotives. The last of these options, the most energy-efficient, requires electrification of the system. To be electrified, a means of supplying electricity to the train is needed. This can be done with overhead wires or with a third-rail system. The former is the more common method.

Depending on how much traffic they carry, railways can be built with a varying number of tracks. Rail lines that carry little traffic are often built with a single track used by trains in both directions; on rail lines like these, "crossovers", "passing loops" or "passing sidings", which consist of short stretches of double track, are provided along the line to allow trains to pass each other, and travel in opposite directions. Alternatively, there may be longer sections of the line that are double track - effective timetabling can allow train travel up and down a partially double-track line equivalent to travel on full double tracks. Conversely, double tram track is sometimes interlaced at narrow passages (see tram tracks). Single-track lines are cheaper to build, but can handle only a limited amount of traffic and are consequently mainly used on branch lines.

On busier lines two or more tracks are provided, one or more for each direction of travel. On very busy lines as many as eight tracks (four tracks in each direction) are used to handle large amounts of traffic.

With the advent of containerized freight in the 1960s, rail and ship transportation have become an integrated network that moves bulk goods very efficiently with a very low labor cost. An example is that goods from east Asia that are bound for Europe will often be shipped across the Pacific and transferred to trains to cross North America and be transferred back to a ship for the Atlantic crossing.

Major cities often have metro and/or light rail/tram systems. For a tram on the road the terms streetcar track, tram track or tramway are used, rather than railway or railroad.