Urban rail transit
Many systems in East, Southeast and South Asia like Taipei, Chennai and Singapore, are called "MRT", which stands for "mass rapid transit".
Other less common names include "T-bane", which stands for "tunnelbana" (in Scandinavia, literally tunnel track) and "MTR" (mass transit railway).
Though many European and East Asian commuter rail systems operate with frequencies and rolling stock similar to that of rapid transit, they do not qualify as such because they share tracks with intercity/freight trains, or they have at grade crossings.
Generally, S-trains share tracks with mainline passenger and freight trains, but the distances between stations and the service headway resemble metro systems.
Larger systems span a variety of conceptual designs, from subway-like advanced rapid transit (ART) systems to smaller (typically two to six passengers) vehicles known as personal rapid transit (PRT) which offer direct point-to-point travel along a switched network.
Conversely, the Docklands Light Railway in London, C Line in Los Angeles, and some metro lines in China are referred to as "Light Rail" but qualify as rapid transit because they are fully grade-separated and provide a high frequency of service.
Many cities use names such as subway and elevated railway to describe their entire systems, even if they combine both methods of operation.
The New York City Subway also combines elevated and subterranean stations, and the Chicago "L" and the Vancouver SkyTrain use tunnels to run through central areas.
Some cities experimenting with guided bus technologies, such as Nancy, have chosen to refer to them as 'trams on tires' (rubber-tired trams) and given them tram-like appearances.
In a 2006 article, the political scientist Ted Balaker and the urban planner Cecilia Juong Kim stated that public rail transit provides certain benefits for a community but also that the goals of policymakers are not often met.
They also note some American economists claim that contrary to popular belief, rail transit has failed to improve the environment, serve the poor, or reduce highway congestion in the United States.
