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Light rail, light rail transit (LRT), tram or fast tram is a form of tramway or urban rail transit, using rolling stock, that constitutes a form of tram. They operate at a higher capacity, and often on an exclusive right-of-way, than most historical tramways.

There is no standard definition, but in the United States (where the terminology was devised in the 1970s from the engineering term light railway), light rail operates primarily along exclusive rights-of-way and uses either individual tramcars or multiple units coupled to form a train that is lower capacity and lower speed than a long heavy-rail passenger train or metro system.[1][2][3][4][5]

A few light rail networks tend to have characteristics closer to rapid transit or even commuter rail; some of these heavier rapid transit-like systems are referred to as light metros. Other light rail networks are tram-like in nature and partially operate on streets. Light rail systems are found throughout the world, on all inhabited continents. They have been especially popular in recent years due to their lower capital costs and increased reliability compared with heavy rail systems.

History


Many original tram and streetcar systems in the United Kingdom, United States, and elsewhere were decommissioned starting in the 1950s as the popularity of the automobile increased. Britain abandoned its last tram system, except for Blackpool, by 1962.[7] Although some traditional trolley or tram systems exist to this day, the term "light rail" has come to mean a different type of rail system. Modern light rail technology has primarily West German origins, since an attempt by Boeing Vertol to introduce a new American light rail vehicle was a technical failure. After World War II, the Germans retained many of their streetcar networks and evolved them into model light rail systems (Stadtbahnen). Except for Hamburg, all large and most medium-sized German cities maintain light rail networks.[8]

The basic concepts of light rail were put forward by H. Dean Quinby in 1962 in an article in Traffic Quarterly called "Major Urban Corridor Facilities: A New Concept". Quinby distinguished this new concept in rail transportation from historic streetcar or tram systems as:

  • having the capacity to carry more passengers
  • appearing like a train, with more than one car connected together
  • having more doors to facilitate full utilization of the space
  • faster and quieter in operation

The term light rail transit (LRT) was introduced in North America in 1972 to describe this new concept of rail transportation.[9]

The first of the new light rail systems in North America began operation in 1978 when the Canadian city of Edmonton, Alberta, adopted the German Siemens-Duewag U2 system, followed three years later by Calgary, Alberta, and San Diego, California. The concept proved popular, and although Canada has few cities big enough for light rail, there are now at least 30 light rail systems in the United States.

Britain began replacing its run-down local railways with light rail in the 1980s, starting with the Tyne and Wear Metro and followed by the Docklands Light Railway (DLR) in London. The historic term light railway was used because it dated from the British Light Railways Act 1896, although the technology used in the DLR system was at the high end of what Americans considered to be light rail. The trend to light rail in the United Kingdom was firmly established with the success of the Manchester Metrolink system in 1992.

Definition


The term light rail was coined in 1972 by the U.S. Urban Mass Transportation Administration (UMTA; the precursor to the Federal Transit Administration) to describe new streetcar transformations that were taking place in Europe and the United States. In Germany the term Stadtbahn (to be distinguished from S-Bahn, which stands for Stadtschnellbahn) was used to describe the concept, and many in UMTA wanted to adopt the direct translation, which is city rail (the Norwegian term, bybane, means the same). However, UMTA finally adopted the term light rail instead.[10] Light in this context is used in the sense of "intended for light loads and fast movement", rather than referring to physical weight. The infrastructure investment is also usually lighter than would be found for a heavy rail system.

The Transportation Research Board (Transportation Systems Center) defined "light rail" in 1977 as "a mode of urban transportation utilizing predominantly reserved but not necessarily grade-separated rights-of-way. Electrically propelled rail vehicles operate singly or in trains. LRT provides a wide range of passenger capabilities and performance characteristics at moderate costs."

The American Public Transportation Association (APTA), in its Glossary of Transit Terminology, defines light rail as:

However, some diesel-powered transit is designated light rail, such as the O-Train Trillium Line in Ottawa, Ontario, Canada, the River Line in New Jersey, United States, and the Sprinter in California, United States, which use diesel multiple unit (DMU) cars.

Light rail is similar to the British English term light railway, long-used to distinguish railway operations carried out under a less rigorous set of regulation using lighter equipment at lower speeds from mainline railways. Light rail is a generic international English phrase for these types of rail systems, which means more or less the same thing throughout the English-speaking world.

The use of the generic term light rail avoids some serious incompatibilities between British and American English. The word tram, for instance, is generally used in the UK and many former British colonies to refer to what is known in North America as a streetcar, but in North America tram can instead refer to an aerial tramway,[11] or, in the case of the Disney amusement parks, even a land train.[12] (The usual British term for an aerial tramway is cable car, which in the US usually refers to a ground-level car pulled along by subterranean cables.) The word trolley is often used as a synonym for streetcar in the United States, but is usually taken to mean a cart, particularly a shopping cart, in the UK and elsewhere.[13] Many North American transportation planners reserve streetcar for traditional vehicles that operate exclusively in mixed traffic on city streets, while they use light rail to refer to more modern vehicles operating mostly in exclusive rights of way, since they may operate both side-by-side targeted at different passenger groups.[14]

The difference between British English and American English terminology arose in the late 19th century when Americans adopted the term "street railway", rather than "tramway", with the vehicles being called "streetcars" rather than "trams".

The opposite phrase heavy rail, used for higher-capacity, higher-speed systems, also avoids some incompatibilities in terminology between British and American English, as for instance in comparing the London Underground and the New York City Subway. Conventional rail technologies including high-speed, freight, commuter/regional, and metro/subway/elevated urban transit systems are considered "heavy rail". People movers and personal rapid transit are even "lighter," at least in terms of capacity. Monorail is a separate technology that has been more successful in specialized services than in a commuter transit role.

Types


Due to varying definitions, it is hard to distinguish between what is called light rail, and other forms of urban and commuter rail.

There is a significant difference in cost between these different classes of light rail transit.

The most difficult distinction to draw is that between light rail and streetcar or tram systems.

At the highest degree of separation, it can be difficult to draw the line between light rail and metros. The London Docklands Light Railway would likely not be considered as "light rail" were it not for the contrast between it and the rapid transit London Underground. In Europe and Asia, the term light rail is increasingly used to describe any rapid transit system with a fairly low frequency or short trains compared to heavier mass rapid systems such as the London Underground or Singapore's Mass Rapid Transit. However upon closer inspection, these systems are better classified as light metro or people movers. For instance, Line 1 and Line 3 in Manila are often referred to as "light rail", despite being fully segregated, mostly elevated railways. This phenomenon is quite common in East Asian cities, where elevated metro lines in Shanghai, Wuhan, and Dalian in China; and Jakarta and Palembang in Indonesia are called light rail lines. In North America, such systems are not usually considered light rail.

Many systems have mixed characteristics.

It is even possible to have high-floor rapid transit cars run along a street, like a tram; this is known as street running

In some areas, "light rail" may also refer to any rail line with frequent low speeds or many stops in a short distance.

Reference speed from major light rail systems, including station stop time, is shown below.[17]

However, low top speed is not always a differentiating characteristic between light rail and other systems.

Many light rail systems—even fairly old ones—have a combination of both on- and off-road sections.

Some systems, such as the AirTrain JFK in New York City, the DLR in London, and Kelana Jaya Line in Kuala Lumpur, Malaysia, have dispensed with the need for an operator. The Vancouver SkyTrain was an early adopter of driverless vehicles, while the Toronto Scarborough rapid transit operates the same trains as Vancouver, but uses drivers. In most discussions and comparisons, these specialized systems are generally not considered light rail.

Track gauge


Historically, the track gauge has had considerable variations, with narrow gauge common in many early systems. However, most light rail systems are now standard gauge.[8] Older standard-gauge vehicles could not negotiate sharp turns as easily as narrow-gauge ones, but modern light rail systems achieve tighter turning radii by using articulated cars. An important advantage of standard gauge is that standard railway maintenance equipment can be used on it, rather than custom-built machinery. Using standard gauge also allows light rail vehicles to be moved around, conveniently using the same tracks as freight railways. Another factor favoring standard gauge is that accessibility laws are making low-floor trams mandatory, and there is generally insufficient space for wheelchairs to move between the wheels in a narrow-gauge layout. Furthermore, standard-gauge rolling stock can be switched between networks either temporarily or permanently and both newly built and used standard-gauge rolling stock tends to be cheaper to buy, as more companies offer such vehicles.

Capacity


Energy efficiency for light rail may be 120 passenger miles per gallon of fuel (or equivalent), but variation is great, depending on circumstances.[19]

One line of light rail (requires 25' Right of Way) has a theoretical capacity of up to 8 times more than one 12' lane of freeway (not counting buses) during peak times.

By contrast, light rail vehicles can travel in multi-car trains carrying a theoretical ridership up to 20,000 passengers per hour in much narrower rights-of-way, not much more than two car lanes wide for a double track system.[22] They can often be run through existing city streets and parks, or placed in the medians of roads. If run in streets, trains are usually limited by city block lengths to about four 180-passenger vehicles (720 passengers). Operating on two-minute headways using traffic signal progression, a well-designed two-track system can handle up to 30 trains per hour per track, achieving peak rates of over 20,000 passengers per hour in each direction. More advanced systems with separate rights-of-way using moving block signalling can exceed 25,000 passengers per hour per track.[23]

Most light rail systems in the United States are limited by demand rather than capacity (by and large, most American LRT systems carry fewer than 4,000 persons per hour per direction), but Boston's and San Francisco's light rail lines carry 9,600 and 13,100 passengers per hour per track during rush hour.[24] Elsewhere in North America, the Calgary C-Train and Monterrey Metro have higher light rail ridership than Boston or San Francisco. Systems outside North America often have much higher passenger volumes. The Manila Light Rail Transit System is one of the highest capacity ones, having been upgraded in a series of expansions to handle 40,000 passengers per hour per direction, and having carried as many as 582,989 passengers in a single day on its Line 1.[25] It achieves this volume by running four-car trains with a capacity of up to 1,350 passengers each at a frequency of up to 30 trains per hour. However, the Manila light rail system has full grade separation and as a result has many of the operating characteristics of a metro system rather than a light rail system. A capacity of 1,350 passengers per train is more similar to heavy rail than light rail.

A bus rapid transit (BRT) system using dedicated lanes can have a theoretical capacity of 3,600 passengers per hour per direction (30 buses per direction, 120 passengers in articulated buses). BRT is an alternative to LRT, at least if very high capacity is not needed. Using buses, roads can achieve a much higher commuter capacity than is achievable with passenger cars. To have 30 buses per direction an hour, buses must have priority at traffic lights and have their own dedicated lanes. Buses can travel closer to each other than rail vehicles because of better braking capability. However, each bus vehicle requires a single driver, whereas a light rail train may have three to four cars of much larger capacity in one train under the control of one driver, or no driver at all in fully automated systems, increasing the labor costs of high-traffic BRT systems compared to LRT systems.

The peak passenger capacity per lane per hour depends on which types of vehicles are allowed at the roads.

When there is a bus driving on this route, the capacity of the lane will be more and will increase when the traffic level increases.

(Edson & Tennyson, 2003)

Safety


An analysis of data from the 505-page National Transportation Statistics report [27] published by the US Department of Transportation shows that light rail fatalities are higher than all other forms of transportation except motorcycle travel (31.5 fatalities per 100 million miles).[28]

However, the National Transportation Statistics report [27] published by the US Department of Transportation states that "Caution must be exercised in comparing fatalities across modes because significantly different definitions are used.

For Example in Denver, CO, Arvada, CO, and Wheatridge, CO the RTD’s new G line was built adding a connection from Union Station To Wheatridge it was delayed 2 year for a new safety system that still fails very heavily.

Construction and operation costs


The cost of light rail construction varies widely, largely depending on the amount of tunneling and elevated structures required.

By comparison, a freeway lane expansion typically costs $1.0 million to $8.5 million per lane mile for two directions, with an average of $2.3 million.[31] However, freeways are frequently built in suburbs or rural areas, whereas light rail tends to be concentrated in urban areas, where right of way and property acquisition is expensive. Similarly, the most expensive US highway expansion project was the "Big Dig" in Boston, Massachusetts, which cost $200 million per lane mile for a total cost of $14.6 billion. A light rail track can carry up to 20,000 people per hour as compared with 2,000–2,200 vehicles per hour for one freeway lane,[32]. For example, in Boston and San Francisco, light rail lines carry 9,600 and 13,100 passengers per hour, respectively, in the peak direction during rush hour.[24]

Combining highway expansion with LRT construction can save costs by doing both highway improvements and rail construction at the same time.

LRT cost efficiency improves dramatically as ridership increases, as can be seen from the numbers above: the same rail line, with similar capital and operating costs, is far more efficient if it is carrying 20,000 people per hour than if it is carrying 2,400.

However, Calgary's LRT ridership is much higher than any comparable US light rail system, at 300,000 passengers per weekday, and as a result its capital efficiency is also much higher.

Compared to buses, costs can be lower due to lower labor costs per passenger mile, higher ridership (observations show that light rail attracts more ridership than a comparable bus service) and faster average speed (reducing the number of vehicles needed for the same service frequency).

Health impact


Integration with bicycles


Light rail lines have various policies on bicycles.[37] Some fleets restrict bicycles on trains during peak hours.

Variations


Around Karlsruhe, Kassel, and Saarbrücken in Germany, dual-voltage light rail trains partly use mainline railroad tracks, sharing these tracks with heavy rail trains. In the Netherlands, this concept was first applied on the RijnGouweLijn. This allows commuters to ride directly into the city centre, rather than taking a mainline train only as far as a central station and then having change to a tram. In France, similar tram-trains are planned for Paris, Mulhouse, and Strasbourg; further projects exist. In some cases, tram-trains use previously abandoned or lightly used heavy rail lines in addition to or instead of still in use mainline tracks.

Some of the issues involved in such schemes are:

  • compatibility of the safety systems
  • power supply of the track in relation to the power used by the vehicles (frequently different voltages, rarely third rail vs overhead wires)
  • width of the vehicles in relation to the position of the platforms
  • height of the platforms

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 (now the Norristown High Speed Line). Such arrangements are almost impossible now, due to the Federal Railroad Administration refusing (for crash safety reasons) to allow non-FRA compliant railcars (i.e., subway and light rail vehicles) to run on the same tracks at the same times as compliant railcars, which includes locomotives and standard railroad passenger and freight equipment. Notable exceptions in the US are the NJ Transit River Line from Camden to Trenton and Austin's Capital MetroRail, which have received exemptions to the provision that light rail operations occur only during daytime hours and Conrail freight service only at night, with several hours separating one operation from the other. The O-Train Trillium Line in Ottawa also has freight service at certain hours.

When electric streetcars were introduced in the late 19th century, conduit current collection was one of the first ways of supplying power, but it proved to be much more expensive, complicated, and trouble-prone than overhead wires. When electric street railways became ubiquitous, conduit power was used in those cities that did not permit overhead wires. In Europe, it was used in London, Paris, Berlin, Marseille, Budapest, and Prague. In the United States, it was used in parts of New York City and Washington, D.C.[39] Third rail technology was investigated for use on the Gold Coast of Australia for the G:link light rail,[40] though power from overhead lines was ultimately utilized for that system.

In the French city of Bordeaux, the tramway network is powered by a third rail in the city centre, where the tracks are not always segregated from pedestrians and cars.[41] The third rail (actually two closely spaced rails) is placed in the middle of the track and divided into eight-metre sections, each of which is powered only while it is completely covered by a tram. This minimises the risk of a person or animal coming into contact with a live rail. In outer areas, the trams switch to conventional overhead wires. The Bordeaux power system costs about three times as much as a conventional overhead wire system, and took 24 months to achieve acceptable levels of reliability, requiring replacement of all the main cables and power supplies.[42] Operating and maintenance costs of the innovative power system still remain high. However, despite numerous service outages, the system was a success with the public, gaining up to 190,000 passengers per day.

Comparison to other rail transit modes


With its mix of right-of-way types and train control technologies, LRT offers the widest range of latitude of any rail system in the design, engineering, and operating practices.

The BART railcar in the following chart is not generally considered to be a "light rail" vehicle (it is actually a heavy rail vehicle), and is only included for comparison purposes.

An important factor crucial to LRT is the train operator.

The latest generation of LRVs has the advantage of partially or fully low-floor design, with the floor of the vehicles only 300 to 360 mm (11.8 to 14.2 in) above the top of the rail, a feature not found in either rapid rail transit vehicles or streetcars.

Overhead lines supply electricity to the vast majority of light rail systems. This avoids the danger of passengers stepping on an electrified third rail. The Docklands Light Railway uses an inverted third rail for its electrical power, which allows the electrified rail to be covered and the power drawn from the underside. Trams in Bordeaux, France, use a special third-rail configuration where the power is only switched on beneath the trams, making it safe on city streets. Several systems in Europe and a few recently opened systems in North America use diesel-powered trains.

Tram and other light rail transit systems worldwide


Around the world there are many tram and streetcar systems.

A number of UK cities have substantial light rail networks including Nottingham, Manchester and a line between Birmingham and Wolverhampton, with plans to extend out as far as Coventry.

See also


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