Medium capacity rail transport system

Defining characteristics

The definition of a medium-capacity system varies due to its non-standardization. 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), 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, and a report from the World Bank places the capacity of an MCS at 15,000–30,000 p/h/d. 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, while light rail systems have passenger capacity volumes of around 10,000–12,000 p/h/d or 12,000–18,000 p/h/d. However, passenger capacity volume is just one possible criterion used to define a medium-capacity rail transit system.

Another criterion that can be used to define a medium-capacity rail system is vehicle type. 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. 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.

Variants of the term

"Light metro" is a common alternative term used to describe the system worldwide. The term is used in European countries, India, and South Korea. In some countries, however, light metro systems are conflated with light rail. For example, in South Korea, the U Line in Uijeongbu utilizes VAL system, a variant of medium-capacity rail transport, and is therefore categorized "light metro" by LRTA and others, though some sources refer as to the U Line as "light rail". Busan–Gimhae Light Rail Transit is also akin to a light metro in its appearance and features, thought the operator categorizes it a "light rail". In India as well some articles also refer to some "light metro"-type systems as "light rail".

As mentioned above, VAL (Véhicule Automatique Léger) systems are categorized in the medium-capacity rail systems family because their manufacturer defines their passenger capacities as being up to 30,000 p/h/d. A nonprofit organization, the Light Rail Transit Association (LRTA) also categorizes several public transport systems as "light metro".

In Hong Kong, MTR's Ma On Shan Line could, in some contexts, be classified as a MCS (as it has used shorter four-car SP1950 trains) but can attain up to 32,000 p/h/d which is comparable to the passenger capacity of some full metro transit networks. This classification will not last for much longer as full-length, 8-car trains are being deployed on the line in advance of its merger with the West Rail Line to form the East-West Corridor by 2019. 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 built to MCS standards, though the latter can eventually be expanded to full metro if passenger demand increases.

Advantages and disadvantages

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. 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 MCS/light metro systems

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

Former examples

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