The Mumbai Metro is a metro system serving in the Indian city of Mumbai. The system is designed to reduce traffic congestion in the city, and supplement the existing, but severely overcrowded Mumbai Suburban Railway network. It will be built in three phases over a 15-year period, with overall completion expected in 2021. When complete, the core system will comprise three high-capacity metro railway lines, spanning a total of 63 kilometres (39 mi). Line 1 of the Mumbai Metro is operated by Mumbai Metro One Pvt Ltd (MMOPL), a joint venture company formed by Reliance Infrastructure, Veolia Transport and the Mumbai Metropolitan Region Development Authority (MMRDA).