|Central Underground Station|
|Owner||Singakangia Transport Authority|
|Transit type||Mass Transit|
|Daily ridership||3.879 million|
|Headway||2 to 10 minutes|
|First departure||4 am|
|Last arrival||11.59 pm|
|Track gauge||1,435 mm (4 ft 8 1⁄2 in)|
The Singkangian Underground, or the SU for short, is a rapid transit system forming the major component of the railway system in Singkangia, spanning the entire city-state. The lines are built by the Land Transport Authority, a statutory board of the Government of Singkangia, which allocates operating concessions to the profit-based corporations, SMRT Corporation and SBS Transit.
The plans to build up the Singkangian Metro was laid out by the Communist Transportation Minister Kan Buowei. Due to traffic congestion, and to impress foreigners when visiting Communist Singkangia, the Underground was decided as the best mode of transportation.
The first line was built from Changkee Airport to Central (Odessa), and was completed by 1951. Soviet workers did the labor and the art work, but the main engineering designs, routes, and construction plans were handled by specialists recruited from the Mergan Bahn. The Mergans called for tunneling instead of the "cut-and-cover" technique, the use of escalators instead of lifts, the routes, and the design of the rolling stock.
Subsequent lines were built further underground, so that they double as Nuclear shelters. The second line from Marnata to Central, called the Aspen Line, was completed in 1954. The next one, then called the Keppong Line, stretching from Central to Keppong.