Line 4 (Chennai Metro)

The Orange Line or Line 4 is one of the planned lines of Chennai Metro. It is part of the second phase of the project and the under construction line stretches from to. The line will consist of 27 stations, out of which nine will be underground and 18 will be at grade or elevated.

Phase II
The construction of the first phase of Chennai Metro started in June 2009. Commercial operations started on the green line in June 2015. On 10 February 2019, the extension of blue line was opened, completing the first phase of the metro.

In July 2016, Government of Tamil Nadu announced that the second phase would have three lines totaling 104 km in length with 104 stations. Two corridors would extend from Madhavaram connecting with Siruseri and Sholinganallur respectively with the third corridor connecting Koyambedu with Lighthouse. In July 2017, the state government announced an extension in Phase II, involving an extension of line four from Lighthouse up to Poonamallee with an intersection with the Madhavaram–Sholinganallur line at Alwarthirunagar. The line will extend to 26.1 km with 16 km elevated and 10.1 km underground. It will consist of 30 stations including 12 undergrounds stations. The stations for the second phase were designed to be smaller than the existing stations operational in the first phase.

On 20 November 2020, foundation stone for the second phase was laid and construction commenced. In November 2022, Alstom was awarded the contract to supply metro coaches for the phase II expansion. In May 2023, CMRL announced a revised plan for the second phase revising the station count on the fourth line to 27. As per the final plan, the fourth line will extend for 26.1 km.

The second phase is estimated to cost inr 632460000000 of which initially inr 47100000000 was loaned by JICA. On 14 February 2021, Prime Minister of India announced that the government has set aside inr 630000000000 for the construction of phase II and further extension.

Phase II extension
In 2022, the state government proposed an extension plan for the fourth line from Poonamalee to Parandur, covering an approximate 43.6 km. In early 2024, feasibility report was submitted by CMRL for the proposed expansion of the line, green lighting the same.

Stations
under construction