off with the reliability of the MRT lines improving by almost ten-fold by 2019. Urban rail transit Mass Rapid Transit (MRT) The Mass Rapid Transit, which opened in 1987, is a heavy rail metro system that serves as the major backbone of Singapore's public transport system along with public buses; as of 2022, the network has a length of and 134 stations. The Land Transport Authority plans to provide a more comprehensive rail transport system by expanding the rail system to a total of by the year 2030, with eight in ten households living within a 10-minute walking distance of an MRT station. The current MRT network consists of six main lines: the North South Line, East West Line, Circle Line and Thomson–East Coast Line operated by SMRT Trains (SMRT Corporation) and the North East Line and Downtown Line operated by SBS Transit. Two more lines, the Jurong Region Line and the Cross Island Line, will open in stages from 2027 and 2030 respectively. Light Rail Transit (LRT) In several new towns, automated rubber-tyred light rail transit systems function as feeders to the main MRT network in lieu of feeder buses. The first LRT line, which is operated by SMRT Light Rail, opened in Bukit Panjang in 1999 to provide a connection to Choa Chu Kang in neighbouring Choa Chu Kang New Town. Although subsequently hit by over 50 incidents, some of which resulted in several days of system suspension, similar systems albeit from a different company were introduced in Sengkang and Punggol in 2003 and 2005 respectively, both operated by SBS Transit. Trams Trams twice operated in Singapore: a steam tram from 1886 to 1894 and an electric tram from 1905 to 1927. Both attempts were unsuccessful and the second attempt was replaced with trolley buses. Airport people mover Changi Airport, the main international airport of Singapore, is served by an automated rubber-tyred Skytrain system which first opened in 1990 to connect both the landside and airside of Terminals 1 and 2 when the latter terminal opened the same year. From 2004 to 2007, the original Adtranz C-100 system was replaced with the Mitsubishi Crystal Mover when the system was upgraded and expanded to Terminal 3. In 2019, six more vehicles were phased in and three-car services between Terminals 2 and 3 were introduced to expand the capacity of the system. An underground airport people mover system will also