By the early 2000s, India's capital New Delhi faced dire traffic congestion and air pollution. When the Delhi Metro opened in 2002, few successful public transit examples existed for a country at India's development level. Today, it is a global model.

In March, a new line completion made Delhi's subway longer than New York City's, for a total cost of roughly $10 billion -- less than New York spent to build a 3.5-mile tunnel. Gerald Ollivier, the World Bank's lead transport specialist for India, stated it proved a complex urban rail project in a low- and middle-income country can be delivered to high standards. The Delhi Metro is the world's first railway project awarded carbon credits by the United Nations.

The system is 33 percent solar-powered, and its train cars capture brake energy in batteries. Last year, trains ran 99.9 percent on time. E.

Sreedharan, the managing director of the Delhi Metro Rail Corporation and joint owner with the Delhi and federal governments, earned the nickname "Metro Man of India" for his fearless leadership and zero tolerance for corruption. He instilled professionalism and discipline by sending deputies to study the world's best subway systems and hiring experienced contractors. Despite early tragedies, including crane collapses in 2008 and 2009 killing seven people, Sreedharan took responsibility.

To orient residents new to subways, the Metro hired drama troupes for street plays and introduced smart cards to replace hoarded tokens, transforming commuter habits.