Light metro

Light metro, light rapid transit (LRT) or a medium-capacity system (MCS), is a rail transport system with a capacity greater than light rail, but less than rapid transit. It typically resembles a rapid transit system in terms of infrastructure, but typically features shorter (2–4 car) trains and smaller stations, and may have a differing network topology.

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 system and a rapid transit system, a light metro project is indicated. A light metro system may also result when a rapid transit system fails to achieve the requisite ridership due to network inadequacies (e.g. single-tracking) or changing demographics.

In contrast with light rail systems, a light metro system runs on an entirely grade separated exclusive right of way, and is therefore completely separated from other traffic. In some cases, the distance between stations is much longer than typically found on rapid transit systems. A light metro system 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. However, despite their smaller trains, some light metro systems can rival rapid transit networks in terms of capacity thanks to automatic train operation allowing extremely high-frequency service.

Definition

Light metro systems typically feature shorter trains and smaller stations than rapid transit; this is typically their defining feature. Automatic train operation is more common on light metro systems than rapid transit systems, which has allowed some systems to achieve extremely high frequency, with headways as close as 90 seconds during peak hours, making them competitive with traditional human-driven metro systems in terms of capacity.

Rubber-tyred metro technology, such as the VAL system used on the Taipei Metro, is sometimes used for light metro systems, due to its low running noise, as well as the ability to climb steeper grades and turn tighter curves, thus allowing more flexible alignments.

Rapid transit systems generally have train headways of 10 minutes or better during peak hours. Some systems that qualify as rapid transit in other technical respects (e.g. are fully grade separated), but which have network inadequacies (e.g. a section of single track rail) which cap headways, resulting in decreased capacity, and thus would be more accurately defined as light metro systems as a result.

Capacity

A report from the World Bank places the capacity of a light metro system at 15,000 to 30,000 p/h/d. For comparison, ridership capacity of more than 30,000 p/h/d has been quoted as the standard for rapid transit systems, while light rail systems have passenger capacity volumes of around 10,000 to 12,000 p/h/d or 12,000 to 18,000 p/h/d. VAL (Véhicule Automatique Léger) systems are categorised as light metro because their manufacturer defines their passenger capacities as being up to 30,000 p/h/d.

However, the capacity boundaries for a line to be categorised as a light metro system varies according to the standard used, sometimes even within a single country. For example, the Taiwan Ministry of Transportation and Communications states that each "medium-capacity system" can board around 6,000 to 20,000 passengers per hour per direction (p/h/d or PPHPD), while the Taiwan Department of Rapid Transit Systems defines a capacity of 20,000 to 30,000 p/h/d, which approaches many rapid transit systems, as "medium-capacity systems".

In Hong Kong, MTR's Ma On Shan line was locally classified as a "medium-capacity system" (as it used shorter 4-car SP1950 trains, compared to 7- to 12-car trains on other MTR lines) but can attain up to 32,000 p/h/d which is comparable to the passenger capacity of some rapid transit systems. However, it was built to the full rapid transit standard as it was designed to be extended. Full-length, 8-car trains were deployed on the line in advance of its extension into the Tuen Ma line in June 2021. Two other lines, the Disneyland Resort line shuttle service since 2005 and the South Island line since December 2016, are also classified as "medium-capacity systems" because of their shorter trains and smaller capacity, however they use the same technology as the other rapid transit lines.

Terminology

"Light metro" is a common term in European countries, India, and 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". For example, the U Line in Uijeongbu utilises the VAL system, categorized as a variant of light metro by the LRTA and other organizations, though the operator itself and South Korean sources refer to the U Line as "light rail". Busan–Gimhae Light Rail Transit is also akin to a light metro system in its appearance and features, thought the operator refers it as a "light rail". Likewise, Malaysian officials and media commonly refer to the Kelana Jaya, Ampang and Sri Petaling lines as "light rail transit" systems; 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". The Light Rail Transit Association (LRTA), a nonprofit organisation, also categorises several public transport systems as "light metro".

Advantages and disadvantages

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

Light metro systems may operate faster than rapid transit systems due to shorter dwell times at stations, and the faster acceleration and braking 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, while the shorter automated SkyTrains make all stops.

Light metro 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 handle more spacious trains when demand warrants them. The Taipei Metro, for example, constructed extra space for two extra cars in all its Wenhu Line stations. Alternatively, automatic train operation may be introduced, or at least provided for, allowing for very tight headways, increasing capacity through frequency rather than vehicle size.

List of light metro systems

The following is the list of currently-operating light metro systems as categorized by the Light Rail Transit Association (LRTA) as of March 2018[update], unless otherwise indicated. The lists do not include monorails and urban maglev, despite most of them also being "medium-capacity" rail systems.

Currently operating light metro systems

Under construction light metro systems

Former light metro systems

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

• Guangzhou, China Line 3 – began with 3-car configuration, changed to 6-car in 2010.
• Komaki, Japan Peachliner – abandoned on 30 September 2006.
• Seoul, South Korea Line 9 – trains lengthened from 4 cars to 6 cars in 2019.
• Sha Tin and Ma On Shan, Hong Kong Ma On Shan Rail – converted from 4- to 8-car configuration and became part of Tuen Ma line.
• Toronto, Ontario Line 3 Scarborough – Categorised by APTA as being "intermediate rail" (i.e. between "heavy rail" and "light rail"), and categorised as a "light metro" system by LRTA. Scheduled to cease operations in November 2023, service was suspended following a derailment in July 2023 and was not resumed, instead being replaced by an express bus service.

See also

• Automated guideway transit
• Maglev
• Metro
• Passenger rail terminology
• People mover
• Rail transport
• Rubber-tyred metro
• Urban rail
• VAL

Notes

Bibliography

• Taplin, Michael. . lrta.org. Light Rail Transit Association. Archived from on 2019-04-06.
• . uitp.org. International Association of Public Transport (French: L'Union internationale des transports publics (UITP)).
• Schwandl, Robert. . UrbanRail.Net.

External links

• by the US Transportation Research Board and the American Public Transportation Association
• 2014-11-29 at the Wayback Machine