[2] In December 2007, Chennai Metro Rail Limited (CMRL) was incorporated and the Government of India gave approval for the project in January 2009.

[8][9][10] After approvals from RDSO and the Commissioner of Metro Rail Safety, commercial operations started between Alandur and Koyambedu stations on the green line in June 2015.

[16] A 9 kilometres (5.59 mi) northern extension of the blue line running from Washermanpet to Wimco Nagar consisting of nine stations.

[19][20] The line opened for passenger traffic on 14 February 2021, increasing the length of the operational metro system to 54.1 km (33.62 mi).

[27] The trains are air-conditioned with electrically operated automatic sliding doors and have a first-class compartment with a dedicated section reserved for women.

In the underground sections, a walkway runs along the length with cross passages every 250 metres (820 ft 3 in) for the maintenance and emergency evacuation.

[42][43] The main operational control center (OCC) is located in Koyambedu where the movement of trains and real-time CCTV footage obtained is monitored.

[44] In 2022, an elevated depot at Wimco Nagar covering an area of 3.5 ha (8.6 acres) commenced operations with facilities for inspection, emergency repair and a washing plant.