Passenger rail terminology
Various terms are used for passenger rail lines and equipment. Unfortunately the usage of these terms differs substantially between areas.
Table of contents
Originally, the term rapid transit was used beginning in the 1800s to describe new forms of quick urban public transportation that separated the right-of-way from street traffic. This set rapid transit apart from horsecars, trams, streetcars, omnibuses, and other forms of public transport.
Though the term was almost always used to describe rail transportation, other forms of transit were sometimes described by their proponents as rapid transit, even including local ferries in some cases.
Subway, where it is used in a transit sense, always refers to either a rapid transit system or rarely a light rail/streetcar system that goes underground. The term may refer only to the underground parts of the system, or to the full system.
Subway is most commonly used in the United States and some parts of Canada, though the term is also used elsewhere, such as to describe the subway line in Glasgow, Scotland and in translation of system names or descriptions in some Asian cities into English.
Some lines described as subway use light rail equipment. Notably, the Newark City Subway and Boston's Green Line, each about half underground, originated from fully surface streetcar lines. Sometimes the term is qualified, such as in Philadelphia, where trolleys operate in an actual subway for part of their route and on city streets for the remainder. This is locally styled subway-surface.
In some cities where subway is used, it refers to the entire system; in others, only to the portions that actually are underground. Naming practices often select one type of placement in a system where several are used; there are many subways with above-ground components, and on the other hand, the Vancouver SkyTrain and Chicago El include underground sections.
Bus subways are uncommon but do exist, though in these cases the non-underground portions of route are not called subways. Seattle, Washington has a bus subway downtown, in which dual-fuel buses can operate on overhead wires when in the subway and via internal combustion when outdoors. Bus subways are sometimes built to provide an exclusive right-of-way for bus rapid transit lines, such as the MBTA Silver Line in Boston. These are usually called by the term bus rapid transit.
Underground and metro
Many Germanic languages use names meaning underground railway, while many others use metro. In London, the word metro most commonly refers not to the London Underground and Docklands Light Railway, but to frequent suburban National Rail train services.
The Brussels Metro has three traditional rapid transit lines and two premetro lines which run trolleys but have enough width to be eventually converted to the bigger metro standards if the traffic warrants it.
Elevated is a shortened form of elevated railway, a railway built on supports over other rights of way, generally city streets. They are also called els. In the United States, only the Chicago 'L' is known by that name ('L' is short for elevated).
At-grade urban rail transit
The term streetcar is generic to most forms of common carrier rail transit that runs or has run on streets, providing a local service and picking up and discharging passengers at any street corner, unless otherwise marked.
In the Tennessee Williams play, A Streetcar Named Desire, the term streetcar is used allegorically to refer to Blanche duBois' promiscuousness and inability to form permanent relationships, as in the sarcastic phrase: "Men (or women) are like streetcars. There'll be another one along any minute." There was actually a streetcar line in New Orleans named Desire Street and simply signed Desire. It is mentioned in the book and an actual New Orleans streetcar with that signage is seen at the beginning of the Marlon Brando-Vivien Leigh film.
The name tram is from Low German traam, meaning the "beam (of a wheelbarrow)", although some sources claim that it is derived from the name of engineer Benjamin Outram. It is typically used in Europe to describe any [whatever we decide to call stuff below rapid transit] system.
In the U.S. a tram is a tourist bus in the appearance of a heritage streetcar, a suspended cable car (aerial tramway), or a rubber-tired people-mover used for parking lot shuttles at theme parks and major events.
In the U.S., interurban refers to a higher-speed rural streetcar line. Interurbans are all but gone, with the few remaining (Norristown High Speed Line, IRT Dyre Avenue Line) having been upgraded to rapid transit specifications.
Interurbans sometimes used freight railways rather than building their own track.
In Australia, interurban refers to long distance commuter trains such as the routes between Newcastle and Sydney, or between Brisbane and the Gold Coast. These do not have the features of "intercity trains" in other parts of the world, such as booked seats and meal services, but are bare commuter trains. They are properly called interurban rather than intercity, although CityRail refers to its interurban services as "intercity" trains.
Light rail is a term coined in the 1970s during the reemergence of streetcars/trams. In general, it refers to a streetcar/tram system with certain rapid transit-style features. It is named to distinugish it from heavy rail, which refers to rapid transit systems as well as heavier regional rail/intercity rail.
A few systems such as people movers and personal rapid transit could be considered as even "lighter", at least in terms of how many passengers are moved per vehicle and the speed at which they travel. Monorails are also considered to be a separate technology.
Light rail systems can typically handle steeper inclines than heavy rail, and curves sharp enough to fit within street intersections (though this is hardly true for all light-rail lines). They are typically built in urban areas, providing frequent service with small, light multiple-unit trains or single cars.
The most difficult distinction to draw is that between light rail and streetcar/tram systems. There is a significant amount of overlap between the technologies, and it is common to classify streetcars/trams as a subtype of light rail rather than as a distinct type of transportation. The two general versions are:
- The traditional type, where the tracks and trains run along the streets and share space with road traffic. Stops tend to be very frequent, but little effort is made to set up special stations. Because space is shared, the tracks are usually visually unobtrusive.
- A more modern variation, where the trains tend to run along their own right-of-way and are often separated from road traffic. Stops are generally less frequent, and the vehicles are often boarded from a platform. Tracks are highly visible, and in some cases significant effort is expended to keep traffic away through the use of special signaling and even grade crossings with gate arms.
- At the highest degree of separation, it can be difficult or impossible to draw the line between light rail and rapid transit, as in the case of London's Docklands Light Railway, which would likely not be called light rail were it not for the contrast between it and the London Underground.
Many light rail systems — even fairly old ones — have a combination of the two, with both on-road and off-road sections. In some countries, only the latter is described as light rail. In those places, trams running on mixed right of way are not regarded as light rail, but considered distinctly as streetcars or trams. However, the requirement for saying that a rail line is "separated" can be quite minimal — sometimes just with concrete "buttons" to discourage automobile drivers from getting onto the tracks.
There is a significant difference in cost between these different classes of light rail transit. The traditional style is often less expensive by a factor of two or more. Despite the increased cost, the more modern variation (which can be considered as "heavier" than old streetcar systems, even though it's called light rail) is the dominant form of new urban rail transit in the United States. The Federal Transit Administration helps to fund many projects, but as of 2004, the rules to determine which projects will be funded are biased against the simpler streetcar systems (partly because the vehicles tend to be somewhat slower). Some places in the country have set about building the less expensive streetcar lines themselves or with only minimal federal support. Most of these lines have been "heritage" railways, using refurbished or replica streetcars harkening back to the first half of the 20th century. However, a few, such as the Portland Streetcar, use modern vehicles. There is a growing desire to push the Federal Transit Administartion to help fund these startup lines as well.
Light rail is generally powered by electricity, usually by means of overhead wires, but sometimes by a live rail, also called third rail (a high voltage bar alongside the track), requiring safety measures and warnings to the public not to touch it. In some cases, particularly when initial funds are limited, diesel-powered versions have been used, but it is not a preferred option. Some systems, such as the JFK Airtrain in New York City, are automatic, dispensing with the need for a driver; however, such systems are not what is generally thought of as light rail, crossing over into rapid transit. Automatic operation is more common in smaller people mover systems than in light rail systems, where the possibility of grade crossings and street running make driverless operation of the latter inappropriate.
Regional rail and Commuter rail
See Regional rail.