The Mumbai Metro is a rapid transit

Rapid transit

A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...

 system being built in Mumbai

Mumbai

Mumbai , formerly known as Bombay in English, is the capital of the Indian state of Maharashtra. It is the most populous city in India, and the fourth most populous city in the world, with a total metropolitan area population of approximately 20.5 million...

, India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

's largest city. The system is designed to reduce the rapidly-growing city's congestion problems, and will be built in three phases over a 15-year period, with overall completion expected in 2021. The Metro's operator is Mumbai Metro One Private Limited (MMOPL), a joint venture company formed by Reliance Energy Limited, Veolia Transport and the Mumbai Metropolitan Region Development Authority

Mumbai Metropolitan Region Development Authority

Mumbai Metropolitan Region Development Authority , commonly abbreviated as MMRDA, is a body of the Government of Maharashtra that is responsible for the infrastructure development of the Mumbai Metropolitan Region...

 (MMRDA).

In June 2006, the Prime Minister of India

Prime Minister of India

The Prime Minister of India , as addressed to in the Constitution of India — Prime Minister for the Union, is the chief of government, head of the Council of Ministers and the leader of the majority party in parliament...

, Dr.