In rail transport, a medium capacity system (MCS) is a non-universal term coined to differentiate an intermediate system between light rail and heavy rail. The concept is similar to Light Metro, seen in European countries (see section Variants of term.) A medium capacity system is proposed when an area requires a rapid transit service but the predicted ridership falls between the gap of the other two rail tiers. In contrast with light rail, a medium capacity system is usually running on an exclusive right-of-way. Furthermore, the distance between stations is much longer. An MCS may also be a branch connection to another mode of a heavy-capacity transportation system, such as an airport or the main route of a metro network.
The definition of a medium capacity system varies due to its non-standardization
. This can exist even within a relatively small country. For example, the Taiwan Ministry of Transportation and Communication
states that each train can board 6,000 ~ 20,000 passengers per hour per direction (p/h/d
). However, the Taiwan Department Rapid Transit Systems
suggests an MCS has a capability of boarding 20,000 ~ 30,000 p/h/d
The train may have a shorter configuration than the standard metro system, usually 3 to 6 cars, allowing shorter platforms to be built. Rather than using steel wheels, rubber-tyred metro technology is 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.
Variants of term
The term may vary in different countries. In Russia
, the "Light Metro" (Лёгкое метро) Л1 - Butovskaya Line
has been built to serve the residents of outer Moscow
. This line connects the passengers with the main routes of Moscow Metro
, the French
rubber-tyred fully automated metro system, also applies the term "Light Metro" to define its capacity (up to 30,000 p/h/d.) These can thus also be categorized into the medium capacity system family.
Medium capacity systems have a latent weakness in that as the service district's population increases, the increased transportation demand might create bottlenecks
. But it is hard to extend the platforms once in operation, since it must be done without interfering with traffic, especially for the underground railway systems. Some railway planners may make provisions such as longer platforms than necessary so that they will be capable of accommodating trains with more or longer carriages. The Ma On Shan Line
in Hong Kong
has even applied the metro standard (with less car configuration) for a possible link
with the other existing heavy rail route without reconstructing the current system.