The MRT (Mass Rapid Transit), sometimes referred to as the Bangkok Metro, is Bangkok's underground metro system. It was constructed under a concession concept. Most civil infrastructure were provided by the government sector, Mass Rapid Transit Authority of Thailand (MRTA), and handed over to their concessionaire under a 25-year concession agreement. Bangkok Metro Company Limited (BMCL) is the only private sector company that won a bid in MRTA's concession contract for the blue line. As MRTA's concessionaire, BMCL provides M&E equipment, including electrical trains, signalling systems, SCADA, communication, PSD, etc. for the subway project and fully operates the system. To maintain the system, BMCL has subcontracted in 10 years to Siemens which was the M&E system supplier since system opeing and 7 years maintenance contract to two local maintenance services for north and south line. The MRT line is officially known in Thai as rotfaifah mahanakhon (รถไฟฟ้ามหานคร) or "metropolitan electric train", but it is more commonly called rotfai taidin (รถไฟใต้ดิน), literally, "underground train". The metro has a fleet of 19 trains; the 19th train entered service in October, 2007 after a major accident.

The Blue Line was opened for a limited public trial period of several weeks starting on 13 April 2004. On 3 July 2004 the line was officially opened at 19:19 local time by HM King Bhumibo and Queen Sirikit, who were accompanied by other members of the royal family. Within 30 minutes of its opening, sightseers filled the system to its maximum capacity, but after the initial rush ridership has settled down to around 180,000 riders daily — considerably lower than projections of over 400,000, despite fares being slashed in half from 12-38 baht to 10-15 baht per trip. From 2006 until 2008, fares ranged between 14-36 baht per trip. The fare was raised to 16-41 Baht on 1 January 2009. (Wikipedia): http://en.wikipedia.org/wiki/MRT_(Bangkok)