Light rail
Light rail is a form of passenger urban rail transit that uses rolling stock derived from tram technology while also having some features from heavy rapid transit.
The term was coined in 1972 in the United States as an English equivalent for the German word Stadtbahn, meaning "city railroad". Different definitions exist in some countries, but in the United States, light rail operates primarily along exclusive rights-of-way and uses either individual tramcars or multiple units coupled together, with a lower capacity and speed than a long heavy rail passenger train or rapid transit system.
Narrowly defined, light rail transit uses rolling stock that is similar to that of a traditional tram, while operating at a higher capacity and speed, often on an exclusive right-of-way. In broader usage, light rail transit can include tram-like operations mostly on streets. Some light rail networks have characteristics closer to rapid transit. When these systems are fully grade-separated, they are referred to as light metros or light rail rapid transit.
Terminology
The term light rail was introduced in 1972 by the U.S. Urban Mass Transportation Administration to describe modernized streetcar systems in Europe and North America.In Germany, the concept was known as Stadtbahn, but UMTA adopted the term light rail instead. The word light refers to lighter infrastructure and capacity requirements compared with heavy rail, rather than to physical weight. Mode classification is usually based on the type of right-of-way.
The American Public Transportation Association defines light rail as:
...a mode of transit service operating single cars or short trains on fixed rails, often partly separated from traffic. Vehicles are typically electric, powered from overhead lines via trolley pole or pantograph, operated by an onboard driver, and may feature either high-platform or low-floor boarding.
In international usage, light rail generally denotes newer tram or streetcar systems, ranging from street-running lines to partly grade-separated networks. People movers are typically lower in capacity, while monorail and automated guideway transit are separate technologies with more specialized applications.
Light rail is distinct from the British English term light railway, which refers to lightly regulated, low-speed mainline railways.
Varieties of English
The term light rail helps avoid regional differences in terminology. In the UK, Australia, Ireland and New Zealand tram refers to a street-running rail vehicle, while in North America it can also mean an aerial tramway or, in amusement parks, a land train. Similarly, trolley means streetcar in North America.In North America, streetcar commonly refers to older vehicles operating in mixed traffic, while light rail is used for newer systems that operate mostly on reserved track. The American term street railway emerged in the 19th century, influenced by the German word Straßenbahn. While Britain abandoned most tramways after World War II, several North American cities—including Toronto, Boston, Philadelphia, San Francisco, Pittsburgh, Newark, Cleveland, and New Orleans—retained theirs. These cities later adopted the term light rail when introducing modern systems alongside older streetcars. Since the 1980s, Portland, Oregon has developed all three types: light rail, streetcar, and aerial tram.
Heavy rail refers to higher-capacity, higher-speed systems such as the London Underground or New York City Subway. Conventional passenger and freight railways are also classified as heavy rail. The main distinction is that light rail vehicles can, where necessary, operate in mixed street traffic.
History
Precursors
By the late 19th century, some cities began placing tramways underground to reduce congestion. Early examples include the Murray Hill Tunnel in New York, adapted for streetcars in 1870, Marseille's Noailles station in 1893, and Boston's Tremont Street subway in 1897, the first purpose-built tram subway in North America and a precursor to today's MBTA Green Line. London's Kingsway tramway subway opened in 1906 to connect tram networks and operated until 1952.Early systems
The "Shaker Heights Rapid Transit" in Cleveland provided an early model of a suburban rail line upgraded for tram-like operation and is now part of the RTA Rapid Transit. In Europe, a suburban railway in The Hague was converted to tram operation in 1927, while in Boston the Highland branch was converted in 1959 to create what became the Green Line D branch, boosting ridership with modern PCC cars. In 1964 Chicago's experimental Skokie Swift demonstrated features later adopted by many U.S. light rail systems.Post-war emergence
Many traditional tram and streetcar systems in the United Kingdom, United States, and elsewhere were closed after the 1950s as investment shifted to cars and buses. Leeds and Glasgow briefly built modernized tram lines during the 1940s, but by 1962 Britain had abandoned all tramways, except for in Blackpool. Modern light rail developed largely in postwar West Germany, where many tram networks were upgraded rather than abandoned. These Stadtbahn systems introduced features such as high-capacity vehicles, dedicated alignments, and underground city-center tunnels. With the exception of Hamburg, nearly all large and most medium-sized German cities retained trams and modernized them into light rail. Similar modernization took place in Zurich, Rotterdam, The Hague, Gothenburg, Brussels, and in Central and Eastern Europe, notably Ostrava.In the United States, American planner H. Dean Quinby defined the concept of a "limited tramway" in 1962, distinguishing it from traditional streetcars by features such as articulated vehicles, multiple doors, and higher capacity.
The term light rail transit was introduced in North America in 1972 to describe these upgraded systems. The first of the new generation opened in 1978 in Edmonton, Alberta, using German Siemens-Duewag U2 vehicles, followed by Calgary and San Diego. These proved successful and inspired many more U.S., Canadian, and Mexican light rail systems.
Global expansion
From the 1980s onward, light rail and modern tramways experienced a renewed expansion worldwide. In Europe, new networks were built in cities that had abandoned trams, such as Nantes, which reopened its tramway in 1985, as well as Grenoble, Paris, Strasbourg, Bordeaux, Dublin, Barcelona, and Bergen. In Britain, modern light rail returned with the Tyne and Wear Metro, Manchester Metrolink, South Yorkshire Supertram and Edinburgh Trams.In North America, the San Diego Trolley became a model for later projects, and the number of U.S. systems roughly doubled between the 1990s and 2010s with expansions in Portland, Los Angeles, Denver, Dallas, Minneapolis and Seattle. Canada added the Ion in Waterloo and the Confederation Line in Ottawa, while Australia introduced the Sydney Light Rail in 1997.
In Asia, the Toyama Light Rail opened in 2006 as Japan's first new tramway in decades. Light rail systems also opened in several Chinese cities, such as Shenyang, Nanjing, Guangzhou, Beijing and Shanghai.
In Africa and the Middle East, new light rail was introduced in Tunis, Rabat, Algiers, Jerusalem, Casablanca, Dubai, Addis Ababa and Lusail.
In South America, projects included the Ayacucho Tram in Medellín and the VLT Carioca in Rio de Janeiro.
Types
It can be hard to distinguish light rail from other forms of urban and commuter rail. A system termed light rail in one city may be considered a streetcar or tram system in another. Conversely, some lines that are called light rail are very close to rapid transit. In recent years, new terms such as light metro have been used to describe medium-capacity systems. Some diesel light rail systems, such as Sprinter, bear little similarity to urban rail, and could alternatively be classified as commuter rail with lightweight trains.There is a history of what would now be considered light rail vehicles operating on heavy rail rapid transit tracks in the US, especially in the case of interurban streetcars. Notable examples are Lehigh Valley Transit trains running on the Philadelphia and Western Railroad high-speed third rail line.
Flexibility
Light rail corridors may constitute a fully segregated corridor, a dedicated right-of-way on a street, an on-street corridor shared with other traffic, a corridor shared with other public transport, or a corridor shared with pedestrians, resulting in a much higher flexibility than heavy rail.Many systems have mixed characteristics. Indeed, with proper engineering, a rail line could run along a street, then go underground, and then run along an elevated viaduct. For example, the Los Angeles Metro Rail's A Line has sections that could alternatively be described as a tramway, a light metro, and, in a narrow sense, rapid transit. This is especially common in the United States, where there is not a popularly perceived distinction between these different types of urban rail systems.