Phase I The
Delhi Metro Rail Corporation was tasked to prepare a project report for the implementation of a metro rail system in Chennai. The first phase was planned with two lines covering with being underground. The first corridor would connect
Washermanpet with
Chennai International Airport extending for with being underground and the second corridor would connect
St.Thomas Mount with
Chennai Central extending for with being underground. The estimated base cost of the first phase was of which 59% was loaned by
Japan International Cooperation Agency (JICA). The Government of India contributed 15% of the cost and the Government of Tamil Nadu financed the remaining 21% of the project. In March 2009, a US$30 million contract was awarded to a consortium of five companies headed by French company
Egis for technical consultancy on the project. In August 2010, the contract for supplying
rolling stock was awarded to
Alstom for US$243 million. In January 2011, a joint venture between
Larsen & Toubro (L&T) and
Alstom was awarded the a contract for design and construction of tracks and a depot at Koyambedu. Contracts for the construction of underground sections of the first phase were awarded to
Gammon India and
Mosmetrostroy in February 2011. In June 2011, the contract for the construction of the ten elevated stations of the first phase was awarded to Consolidated Construction Consortium. The contract for the supply of lifts and escalators was awarded to a joint venture of
Johnson Lifts and SJEC Corporation. The contract for power supply and overhead electrification was awarded to
Siemens for and contracts for automatic fare collection, tunnel ventilation, and air conditioning were awarded to Nippon Signal,
Emirates Trading Agency, and
Voltas respectively. In July 2012, the first
tunnel boring machine was launched and by October that year, eleven machines were operated by three consortia–
Afcons-Transtonnelstroy, L&T and SUCG. In August 2012, a construction worker was killed and six others were seriously injured after a crane failed and crashed at an under construction site near
Pachaiyappa's College and on 10 January 2013, a 22-year-old construction worker was killed and three others were injured at a construction site between
Alandur and
St. Thomas Mount. On 6 November 2013, a test run was conducted along a stretch of track. The project faced several delays and missed deadlines due to problems with land acquisition and cancellation of construction contracts. On 11 January 2014, a crane toppled over, killing a 20-year-old construction worker and seriously injuring another at
Saidapet. On 14 February 2014, the maiden trial run was conducted between
Koyambedu and
Ashok Nagar stations. The metro received the statutory speed certification clearance from the
Research Design and Standards Organisation in August that year. In January 2015, a report was submitted to the Commissioner of Metro Rail Safety (CMRS) for mandatory safety approvals. After inspecting the infrastructure, the CMRS submitted the report to the
Railway Board in April 2015. Operations on the
Green Line between the
Alandur and Koyambedu stations commenced on 29 June 2015. The Blue Line segment from the
Airport and
Little Mount stations commenced operations on 21 September 2016. The first underground section between
Thirumangalam to
Nehru Park on the Green Line opened on 14 May 2017, and the extension to
Chennai central was completed on 25 May 2018 along with the section from the
Saidapet and
AG-DMS stations on the blue line. On 10 February 2019, the underground stretch from AG-DMS to
Washermanpet of Blue Line was opened, marking the completion of the first phase of the metro.
Phase I Extension In 2014, a northern extension of the Blue Line was announced by the Government of Tamil Nadu. The extension would run from Washermanpet to
Wimco Nagar and consist of nine stations. Construction started in July 2016 with the first trial runs conducted in December 2020. The line opened for passenger traffic on 14 February 2021, increasing the length of the operational metro system to . The expansion costed of which 57% was loaned by JICA.
Phase II In July 2016, the Government of Tamil Nadu announced that the second phase would have three lines spanning with 104 stations. Two corridors would extend from connecting with
Siruseri SIPCOT and respectively with the third corridor connecting Koyambedu with on the
Marina beach. In July 2017, the state government announced an extension of Phase II, involving a section from Lighthouse up to with an intersection with the Madhavaram–Sholinganallur line at
Alwarthirunagar. The second phase would span with 128 stations. The stations for the second phase were designed to be smaller than the stations of the first phase to reduce the cost and time of construction. In 2019, the
Madras High Court questioned the state government on the construction method of the tunnels and its impact on the water bodies. The second phase was estimated to cost of which was loaned by JICA. On 20 November 2020, foundation stone for the second phase was laid and construction commenced. On 14 February 2021,
Prime Minister of India announced that the government has set aside for the construction of the second phase and its further extension. In May 2021, the CMRL awarded contracts to
Tata Group, L&T and
HCC-
KEC for the construction of various sections of the second phase. In November 2022, Alstom was awarded a contract to supply rolling stock for the second phase. The contract included a provision for the supply of 78 train sets including 36 driver-less trains. In December 2022, a contract for the installation of tracks was given to KEC–VNC and
Hitachi bagged the contract for the installation of signalling systems. In January 2023,
Rail Vikas Nigam Limited was awarded a contract for the constructions of underground stations and Linxon was given the contract for the installation of
electric traction. In May 2023, the CMRL announced minor changes to the lines' alignment and that nine stations would be scrapped in the revised plan. Hence, the total length of the second phase was reduced to . L&T was contracted for the installation of overhead equipment and control and monitoring systems. Tata Projects was awarded the contract to construct select stations in October. In December, the CMRL awarded the contract to
ST Engineering for the installation of
platform screen doors in the elevated stations of the second phase. In the same month, Shellinfo was awarded a contract for the installation of
automated fare collection systems. In addition to the previously ordered Alstom train-sets, the CMRL invited bids in March 2024 for the supply of 96 train-sets for the second phase. , about of the second phase had been completed. In March 2025, the first trial run on the Phase II network was conducted on a stretch between
Poonamallee and
Mullaithottam on the proposed Yellow Line. In April 2025, trial runs began on a stretch between Poonamallee and stations on the same line. The RDSO conducted inspection on the same stretch in August 2025, and the Railway Board provided approval for the operation of signals on the line in December 2025. After the conclusion of safety checks by the CMRS in February 2026, the operations on to stretch on the Yellow Line is expected to begin in March 2026, with no intermediate stoppages at stations from Alapakkam to Saligramam.
Phase II Extension In 2022, the state government proposed an extension plan spanning for the three under construction lines of the second phase. The proposal involved extension of
Purple Line from Siruseri SIPCOT to Kilambakkam,
Yellow Line from Poonamallee to
Parandur and
Red Line from Koyambedu to
Avadi. The proposed extension of second phase lines from Siruseri to Kilambakkam, Poonamallee to Parandur, and Koyambedu to Avadi were projected to cost , , and respectively. In May 2024, the state government proposed a new extension from Madhavaram to
Ennore. In May 2024, the
Government of Tamil Nadu approved both the extensions of the Red Line from Koyambedu to Pattabiram and Yellow Line from Poonamallee to Parandur at an estimated cost of and respectively, forwarding to
Government of India for final approval.
Integration of MRTS is proposed to be handed over to Chennai Metro In 2017, the state government proposed to integrate the
Chennai Mass Rapid Transit System (MRTS) into the Chennai Metro. In July 2018,
PwC said that the merger would cost around to convert the rolling stock and install other facilities for the merger. On 11 May 2022,
Southern Railway of the Indian Railways granted an in-principle approval for the integration of the MRTS into the metro. As per the plan, the railway would handover the MRTS to the CMRL once the expansion of the MRTS is completed. However, the extended second phase of the MRTS project, connecting Velachery with St. Thomas Mount experienced delays, and was completed in March 2026. Once the takeover is completed, CMRL will upgrade the MRTS system including tracks, security, ticketing system and rolling stock.
Metrolite In 2020, a
light rail was proposed to connect
Tambaram railway station of the existing suburban rail network with Velachery on the MRTS, as part of plans to link the different
urban transit lines in the city. Feasibility studies for the project was commissioned in February 2023 by the
Chennai Unified Metropolitan Transport Authority (CUMTA). In 2025, the government decided to develop the stretch as a regular metro corridor. The CMRL is also involved in the feasibility studies for the development of metro rail transport in the cities of
Coimbatore,
Madurai and
Tiruchirapalli. CMRL developed the
Kathipara Urban Square as a multi-modal transport hub with parking and recreational areas. In 2023, the CMRL proposed the development of
Central Square around its headquarters with commercial complexes and multi-storied buildings. In April 2025, CMRL announced that it has identified public spaces in
Adyar and
Velachery which can be transformed into public spaces similar to Kathipara Urban Square. == Infrastructure ==