High Quality Content by WIKIPEDIA articles! The Mumbai Metro is a rapid transit system under construction in the Indian city of Mumbai. The system is designed to reduce traffic congestion in the city, and will be built in three phases over a 15-year period, with overall completion expected in 2021. When complete, the system will comprise three high-capacity metro railway lines, spanning a total of 63 kilometres (39 mi). The Mumbai Metro`s operator is Mumbai Metro One Pvt Ltd (MMOPL), a joint venture company formed by Reliance Infrastructure, Veolia Transport and the Mumbai Metropolitan Region Development Authority (MMRDA).