Chennai Metro is a rapid-transit system serving the city and was partially commenced on 29 June 2015. To improve the city's public transportation system and prepare the city for the future commuting needs, the Chennai Metro was planned and approved by the state cabinet during 2007 for which construction began on 2009. Phase I of the Chennai Metro network consists of the Blue Line and the Green Line covering a length of 45.1 kilometres (28.0 mi) consisting of 40 stations with Alandur and Chennai Central serving as interchanges. 55% of the corridors in Phase I are underground and the rest are elevated. The first stretch of Phase I, covering seven stations from Koyambedu to Alandur over a distance of , began operation on 29 June 2015. As of March 2023, the entire Phase 1 stretching from Chennai Central to Alandur on the Green line and Wimco Nagar to Chennai International Airport on Blue line are operational, bringing the total operational network over 45 km. With this, the entirety of Phase I is operational. In December 2016, the Chennai Metro Rail Limited (CMRL) announced the Phase-2 of Chennai Metro for a length of 104 km consisting of 104 stations, subject to approval from the State and Central governments. The Phase 2 was subsequently approved in late 2018, with certain provisos, and soil testing for various stations, which are now under construction since 2019. As of April 2019, ridership has risen considerably to around 100,000 daily commuters, post the inaugural of the entire Phase I. Phase I-A, which is an extension of the Blue line from Washermanpet to Thiruvottiyur was inaugurated in 2021.
