What is light rail vs metro?

Rail transport system with moderate capacity

Toronto subway's former Line 3 Scarborough was fully integrated with the rest of the heavy rail network, despite using light metro technology.

A medium-capacity system (MCS), also known as light rapid transit or light metro, is a rail transport system with a capacity greater than light rail, but less than typical heavy-rail rapid transit.[1] MCS's trains are usually 1–4 cars. Most medium-capacity rail systems are automated or use light rail type vehicles.

Since ridership determines the scale of a rapid transit system, statistical modeling allows planners to size the rail system for the needs of the area. When the predicted ridership falls between the service requirements of a light rail and heavy rail or metro system, an MCS project is indicated. An MCS may also result when a rapid transit service fails to achieve the requisite ridership due to network inadequacies (e.g. single-tracking) or changing demographics.

In contrast with most light rail systems, an MCS usually runs on a fully grade separated exclusive right-of-way. In some cases, the distance between stations is much longer than typically found on heavy rail networks. An MCS may also be suitable for branch line connections to another mode of a heavy-capacity transport system, such as an airport or a main route of a metro network.

Definition

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The definition of a medium-capacity system varies due to its non-standardisation. Inconsistencies in international definitions are even reflected within individual countries. For example, the Taiwan Ministry of Transportation and Communications states that each MCS system can board around 6,000–20,000 passengers per hour per direction (p/h/d or PPHPD),[2] while the Taiwan Department of Rapid Transit Systems (TCG) suggests an MCS has a capability of boarding around 20,000–30,000 p/h/d,[3] and a report from the World Bank places the capacity of an MCS at 15,000–30,000 p/h/d.[4] For comparison, ridership capacity of more than 30,000 p/h/d has been quoted as the standard for metro or "heavy rail" standards rapid transit systems,[5] while light rail systems have passenger capacity volumes of around 10,000–12,000 p/h/d[4] or 12,000–18,000 p/h/d.[5] VAL (Véhicule Automatique Léger) systems are categorised in the medium-capacity rail systems because their manufacturer defines their passenger capacities as being up to 30,000 p/h/d.[6] In Hong Kong, MTR's Ma On Shan line could, in some contexts, are classified as a medium-capacity system (as it used shorter four-car SP1950 trains, compared to 7 to 12 car trains on other heavy rail lines) but can attain up to 32,000 p/h/d which is comparable to the passenger capacity of some full metro transit networks.[7] However, it was built to the full heavy rail standard as it was designed to be extended. Full-length, 8-car trains were deployed on the line in advance of its extension and the line was extended into the Tuen Ma line in June 2021. Two other lines, the Disneyland Resort line shuttle service to Hong Kong Disneyland Resort since 2005 and the South Island line since December 2016, are also classified as MCS because of their shorter trains and smaller capacity, however they use the same technology as the full-capacity rapid transit lines.

Generally speaking, medium capacity designation is created from relative lower capacity and/or train configuration comparisons to other heavy rail systems in the same area. For example, the train in an MCS may have a shorter configuration than the standard metro system, usually three (though, in some cases, just two) to six traincars, allowing for shorter platforms to be built and used. Rather than using steel wheels, rubber-tyred metro technology, such as the VAL system used on the Taipei Metro, is sometimes recommended, due to its low running noise, as well as the ability to climb steeper grades and turn tighter curves, thus allowing more flexible alignments.

Fully heavy rail or metro systems generally have train headways of 10 minutes or better during peak hours.[8] Some systems that qualify as heavy rail/metro in every other way (e.g. are fully grade separated), but which have network inadequacies (e.g. a section of single track rail) can only achieve lesser headways (e.g. every 15 minutes) which result in lower passenger volume capacities, and thus would be more accurately defined as "light metro" or "medium-capacity" systems as a result. An example is the LA Metro B/D line during the COVID-19 pandemic, as headways were reduced to every 12-20 minutes on each line.

Terminology

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Train on the Copenhagen Metro

In addition to MCS, light metro is a common alternative word in European countries, India,[9][10] and South Korea.[11]

Ui-Sinseol Line train leaving Solbat Park station in Seoul, South Korea

In some countries, however, light metro systems are conflated with light rail. In South Korea, light rail is used as the translation for the original Korean term, "경전철" – its literal translation is "light metro", but it actually means "Any railway transit other than heavy rail, which has capacity between heavy rail and bus transit".[12][13][14][15] For example, the U Line in Uijeongbu utilises VAL system, a variant of medium-capacity rail transport, and is therefore categorised "light metro" by LRTA and others,[11] though the operator itself and South Korean sources refer to the U Line as "light rail".[16] Busan–Gimhae Light Rail Transit is also akin to a light metro in its appearance and features, thought the operator refers it as a "light rail".[17] Likewise, Malaysian officials and media commonly refer to the Kelana Jaya, Ampang and Sri Petaling lines as "light rail transit" systems;[18][19][20] when originally opened, the original Malay abbreviations for the lines, PUTRA-LRT (Projek Usahasama Transit Ringan Automatik/Automatic Light Transit Joint Venture Project) and STAR-LRT (Sistem Transit Aliran Ringan/Light Flow Transit System) did not clearly distinguish between light rail and light rapid transit. Some articles in India also refer to some "light metro"-type systems as "light rail".[21] The Light Rail Transit Association (LRTA), a nonprofit organisation, also categorises several public transport systems as "light metro".[22][† 1]

Advantages and disadvantages

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The main reason to build a light metro instead of a regular metro is to reduce costs, mainly because this system employs shorter vehicles and shorter stations.

Light metros may operate faster than heavy-rail rapid transit systems due to shorter dwell times at stations, and the faster acceleration and deceleration of lighter trains.[citation needed] For example, express trains on the New York City Subway are about as fast as the Vancouver SkyTrain, but these express trains skip most stops on lines where they operate.

Medium-capacity systems have restricted growth capacities as ridership increases. For example, it is difficult to extend station platforms once a system is in operation, especially for underground railway systems, since this work must be done without interfering with traffic. Some railway systems, like Hong Kong and Wuhan, may make advance provisions for longer platforms, for example, so that they will be able to accommodate trains with more, or longer cars, in the future. Taipei Metro, for example, constructed extra space for two extra cars in all its Wenhu Line stations.

List of medium-capacity rail systems

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The following is the list of currently-operating MCSs which are categorised as light metros by the Light Rail Transit Association (LRTA) as of March 2018 ,[23] unless otherwise indicated.

The list does not include, for example, monorails and urban maglev, despite most of them also being "medium-capacity rail system".

Former examples

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The following is the list of former-MCSs that either developed into a full rapid transit system, or which are no longer in operation:

See also

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Notes

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1. ^

   The French term Métro léger , a literal translation of "light metro", means light rail.

References

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Bibliography

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Portland streetcar by the author.

This article was first published on October 21, 2009. It's still useful information, so we're sharing it again, with a few minor updates.

Despite wide variety in transit systems around the world, here in the United States we only have a few words to describe transit modes, such as commuter rail, heavy rail, and light rail.

In my recent counterpoint post on the Silver Line and the viability of a Dulles Express Line using the Washington and Old Dominion Trail, I touched briefly upon the differences between American and European transit concepts. Because we don’t have many words to describe a variety of systems, it can be difficult to compare and constrast different types of transit, especially those in other countries. With so few words, things get lost in translation.

As far as the Federal Transit Administration is concerned we have only a few words to describe our modes. There are certainly more variations on modes than those found in the National Transit Database’s glossary. Instead of a fixed set of modes, transit systems really fall on more of a continuum.

In this graphic, more local modes serving shorter trips, like guideways and streetcars, appear above more regional modes used for longer trips. Even within a group, some systems have a more regional flavor than others. For instance, BART, while still heavy rail, is closer to a regional rail system than is Washington’s Metro. And Los Angeles’ Red and Purple Lines with far less suburban-serving segments are closer to the subways of the pre-auto era.

Spencer Lepler correctly called Metro a hybrid between subways and commuter rail. Since it is a hybrid, it can’t be considered purely a subway or a commuter rail system. But the FTA doesn’t consider the Washington Metro any different (as a mode) from the Boston T or the New York City Subway.

Metro is a modern heavy rail system, while Boston and New York have pre-auto age heavy rail systems. Chicago’s Green Line is quite different from Washington’s Green Line. The root of these differences comes from the market for which each was built. Chicago’s Green Line was built mainly with walk-to-transit riders in mind, while Washington sought to cater to drivers bound for the central business district from the suburbs.

Chicago by the author.

Washington by the author.

In the comment threads which have sprouted from the various Silver Line posts from last week and this week, many comparisons have been drawn to European systems and systems in other American cities. These other systems are good places to look, because we can gain insight from the variation between modes. Europe is a particularly good place to look to add a little perspective.

Stadtbahn Stuttgart by the author.

Baltimore Light Rail by the author.

Because the distinctions are important, let’s look a little more deeply at nomenclature.

• Streetcars: Streetcars often operate as single units in traffic with curb-side stops. Sometimes they have a semi-exclusive right-of-way, like a median (New Orleans) or private ROW (Mattapan). They often act as feeders to the regional system and mainly serve closer in nieghborhoods. Streetcars are sometimes older systems dating back many years (as with Philadelphia), while modern streetcars are quite in vogue today (as in Portland and Seattle). Other cities have (re)created vintage (San Francisco) or faux-vintage (Charlotte) streetcar lines.
• Light Rail: This mode began appearing in North America in the late 1970s. Light rail offered a cheaper method to create a regional system and have become popular as substitutes to heavy rail. They serve corridors where heavy rail investment is not practical. In some cities, light rail systems take on many of the attributes of heavy rail, including downtown subways (San Francisco, Seattle) and level boarding (Charlotte, St. Louis). Some of these systems were built from scratch and serve as a regional-scale system (Dallas, Portland) while others are direct descendents from streetcar systems that have been upgraded (Pittsburgh).
• Light Metro: I didn't discuss this in the original version of this post, but there are a few Light Metro type systems that are essentially hybrids between Light Rail and Rapid Rail. These systems are entirely grade separated, like Subways and Rapid Rail, but use shorter trains and smaller stations, so have a lower carrying capacity, which is sometimes made up for with higher frequencies. The most well-known example of this is probably Vancouver's SkyTrain. Honolulu is also currently building a Light Metro line.
• Subways: Systems like the New York Subway and the Chicago L are a type of heavy rail. While these types of service are certainly regional in nature, they often serve only the central municipality and not surrounding jurisdictions. Stop spacing is fairly close and speeds are slower than more regional-type services. The defining characteristic of this subset of heavy rail is that ridership is based on walk-to riders rather than drive-to riders.
• Rapid Rail: The modern heavy rail systems constructed in the 1970s, 80s, and 90s were often known as Rapid Rail. In fact, the Rs in BART and MARTA both stand for ‘Rapid’. However the distinction gets a little blurry here. Rapid Rail systems typically serve the metropolitan area as a whole. Like the Washington Metro, surrounding jurisdictions have high levels of service as well. Speeds are faster than on subways and the distance between stops is higher.
• Regional Rail: Regional rail is a subset of FTA’s commuter rail mode. I think of regional rail as different from commuter rail mainly based on service patterns. Regional rail trains, as their name suggests, serve whole regions. They also offer bi-directional and off-peak service in the region. One of the best examples of regional rail is the SEPTA Regional Rail network in Philadelphia. With a center city tunnel based on the S-bahn tunnels in several German cities, the network serves the central city and the suburbs with quick trips. Service frequencies are lower than one would find on Rapid Rail.
• Commuter Rail: Commuter rail, as I pointed out above, typically only offers peak-period, peak-direction service. In the Washington region, VRE and MARC‘s Brunswick Line offer good examples. MARC’s Penn Line, on the other hand, acts more like regional rail.
• Other Modes: The FTA also considers Cable Cars, Inclines, Monorails, and Automated Guideways as rail modes. These tend to serve specialized and smaller markets. Cable cars, for instance, can easily be grouped with streetcars, as they serve similar markets and have similar attributes. Inclines have very limited use, but often serve as vital links within transit systems. Monorails and Automated Guideway systems also tend to serve very localized markets or act as distribution systems. It is possible to build entire systems with these technologies, as is the case with Vancouver’s SkyTrain, but in the United States, they tend to be limited to moving people around central business districts, as is the case in Miami and Detroit.

When comparing American transit modes to those found in Europe, things don’t always translate directly. For instance, while systems like Washington’s Metro or San Francisco’s BART might be thought of as German U-bahns because of their heavy rail designation, they’re actually closer to the S-bahn systems in Berlin and Hamburg and Paris’ RER. Of course, the S-bahn systems in smaller German cities, like Stuttgart and Munich, resemble regional rail.

Looking across the pond can create confusion as well. In London, for instance, the Docklands Light Railway has dramatically improved service to East London. But the system is not light rail in the sense that most American’s think of it. It would be more accurately be described as a Light Metro. FTA would consider it Automated Guideway Transit. The Docklands system, unlike most American light rail systems, is entirely grade separated.

And contributing to the idea that America and Britian are two countries separated by a common language, heavy rail in Britian denotes regional and inter-city trains - not urban subway and rapid rail systems, which is what it means in the United States. Even Dr. Gridlock managed to get that one confused, telling a reader that MARC and VRE are heavy rail. In fact, according to FTA, MARC and VRE are both commuter rail.

MARC train at Greenbelt by the author.

Heavy Rail in Philadelphia by the author.

But looking across the globe for good examples of transit generally yields greater understanding of the continuum, even if it makes it harder to quantify. Karlsruhe in Germany has a unique system known as the Stadtbahn. The Stadtbahn name in Germany usually denotes light rail-type trains, but in Karlsruhe the transit system is a unique hybrid of light rail and regional rail. In the city center, trains run in street. However, some services merge onto the conventional rail network for direct, rapid services to suburban destinations.

Munich and Stuttgart both have large regional rail (S-bahn) networks which feed into a central tunnel in the urban core. These tunnels have high platforms and essentially act as a central subway bolstered by the high frequencies resulting from the combined lines.

S-bahn Munich by the author.

Expanding on this continuum concept, I added short-haul inter-city services, although perhaps a better name for the concept is needed. Amtrak services like the Capitol Corridor in California or Keystone Services in the Mid-Atlantic cater to longer-distance commuters as well as inter-city and inter-region travelers. Additionally, even high-speed services like the Acela offer a quick trip from far-flung suburbs. Joe Biden, for instance, commuted from Wilmington, Delaware daily on the Acela as a Senator.

People often like to put our transit systems in silos, and sometimes people disagree about which silo a particular transit system belongs in (especially in our comment threads). A good example can be to look at four American cities who have upgraded their streetcar systems over the years and one modern system.

In about 1907, Philadelphia opened a subway tunnel for trolleys stretching from City Hall to 40th 22nd Street. The streetcars operated as single cars and required passengers to climb steps to board. Outside of the center city, the cars ran in streets, shared with other traffic. Boston had a nearly identical setup for their trolley subway, which opened in 1897. Over on the west coast, San Francisco's remaining streetcar lines all converged on Market Street and ran at street level through the Financial District until 1980, when the Market Street Subway's upper level opened.

In Philadelphia, the PCC streetcars that had been operating through the trolley subway were replaced by modern vehicles in 1981. These modern vehicles still operate as single cars, and are essentially the same length as a PCC streetcar. and require patrons to climb steps. Even at some of the subway stations, fares are collected on board, rather than via faregates. In Boston, the trolley subway is now known as the Green Line.

In 1976, modern vehicles began to replace the PCC streetcars. These vehicles were longer and articulated, though they still required stepwells for boarding. Fare payment in the subway takes place at faregates in the station allowing for all-door boarding, but riders pay the driver when boarding on the surface portions. The Green Line operates with trains coupled together in sets of up to two cars.

In San Francisco, on the other hand, the opening of the Market Street Subway coincided with the introduction of modern vehicles, replacing the PCC cars. These trains can operate in sets of up to 3 cars and have level boarding in the subway, and at some other stations on the surface, and with proof-of-payment, all-door boarding takes place throughout the system.

So, these three cities went in different directions. Are they all the same mode? Or are two light rail while the other is a streetcar? Or vice-versa? If we take the continuum view, Philadelphia's Subway-Surface lines are definitely the most like a streetcar, while the Muni Metro is the most like a light rail?

What about St. Louis's Metrolink and Pittsburgh's T? They both use the same vehicles, and both operate them in trains of up to 2 cars. Both have a downtown subway. In St. Louis, Metrolink was built from scratch, opening in 1993. In Pittsburgh, the T was converted from a streetcar system in the 1980s, with modern vehicles running starting in 1984 and the subway opening in 1985. Pittsburgh still uses a mix of level, all-door boarding at some stations, and front-door-only stepwell boarding at others. St. Louis is entirely all-door, level boarding. How do these systems compare with each other? How do they compare with the Philadelphia, Boston, and San Francisco examples?

We need to focus less on a rigid structure for naming rail modes. Individual systems possess a richer set attributes beyond just their FTA mode. Thinking of transit systems as lying somewhere on a continuum may help us find better ways of comparing systems across regions and nations.

Matt Johnson has lived in the Washington area since 2007. He has a Master’s in Planning from the University of Maryland and a BS in Public Policy from Georgia Tech. He lives in Dupont Circle. He’s a member of the American Institute of Certified Planners, and is an employee of the Montgomery County Department of Transportation. His views are his own and do not represent those of his employer.