The Ma On Shan line () was a rapid transit line that formed part of the Mass Transit Railway (MTR) system in Hong Kong. Coloured brown on the MTR map, the line acted as a branch of the East Rail line that connects the new towns of Sha Tin and Ma On Shan in the northeastern New Territories. The railway was one of three built by the Kowloon-Canton Railway Corporation (KCRC), which named it as Ma On Shan Rail (, abbreviated as ). Since KCRC's merger of operations with the MTR Corporation on 2 December 2007, the line has been operated as part of the MTR network. The line was integrated into the Tuen Ma line Phase 1 on 14 February 2020 following the partial opening of the Sha Tin to Central Link. Overview and current status Construction of the Ma On Shan line began on 12 February 2001 and it fully opened for service on 21 December 2004, 3 days earlier than the proposed opening date. KCRC estimated the construction costs to be HK$10 billion. Over a thousand passengers took the first train from Tai Wai on the first day of service. Since then, the usage of buses and taxis in the area decreased by as much as 50%. It was reported that some bus routes operated by KMB saw a decrease of ridership by one-third in just a few days. Since the early planning stages, the Ma On Shan line was designed to be capable of joining with the West Rail line. Under Phase 1 the Sha Tin to Central Link project, the Ma On Shan line would be extended from Tai Wai station to Hung Hom station via East Kowloon, with six new intermediate stations, including interchanges with the Kwun Tong line at Diamond Hill and Ho Man Tin, an additional interchange with the East Rail line at Hung Hom, and a new station, Hin Keng, serving Sha Tin. The extension will connect to the West Rail line at Hung Hom and continue on to Tuen Mun station in the northwest New Territories via the current West Rail line and its 2009 extension to Hung Hom). Due to various delays, the new line opened only as far as Kai Tak on 14 February 2020, with the remaining section to Hung Hom to begin service on 27 June 2021. After the opening of the Tuen Ma line Phase