The Bangkok Mass Transit System, commonly known as the BTS or the Skytrain, is an elevated rapid transit system in Bangkok, Thailand. It is operated by Bangkok Mass Transit System PCL, a subsidiary of BTS Group Holdings, under a concession granted by the Bangkok Metropolitan Administration. The system consists of 52 stations along two lines: the Sukhumvit Line running northwards and south-eastwards, terminating at Wat Phra Sri Mahathat and Kheha respectively. The Silom Line which serves Silom and Sathon Roads, the central business district of Bangkok, terminates at National Stadium and Bang Wa. The lines interchange at Siam station and have a combined route length of 53.5 kilometers. The system is formally known as “the Elevated Train in Commemoration of HM the King’s 6th Cycle Birthday”. Besides the BTS, Bangkok’s rapid transit system includes the underground and elevated Mass Rapid Transit railway lines, the Bus Rapid Transit System, and the elevated Airport Rail Link, serving several stations in the city before reaching Suvarnabhumi Airport.