The Tamil Nadu government is reviewing the Chennai Metro's extension plans after two detailed project reports were submitted in February 2025. The first report is for the new 21.8 km line 5b, which would run from Koyambedu to Ambattur, Avadia and Pattabiram along the Outer Ring Road. This line would include 19 overground stations, and the cost is estimated at €1.03 billion (INR 97.44 billion). The second report refers to a 15.5 km extension of line 1 from the airport to Kilambakkam, which would serve 13 overground stations and run parallel to Indian State Railway IR's existing line. The estimated cost of this extension is €98 million.
