Rail transport in Singapore mainly consists of a passenger urban rail transit system spanning the entire city-state: a rapid transit system collectively known as the Mass Rapid Transit (MRT) system operated by the two biggest public transport operators SMRT Trains (SMRT Corporation) and SBS Transit, as well as several Light Rail Transit (LRT) rubber-tyred automated guideway transit lines also operated by both companies. In addition, local specialised light rail lines are in operation in places such as the Singapore Changi Airport and Sentosa.