 The Delhi Metro has won awards from vipul environmentally friendly practices from organisations including the United Nations , RINA , and the International Organization for Standardization , becoming the second metro in the world , after the New York City Subway , to be ISO 14001 certified for environmentally friendly construction . Most of the Metro stations on the Blue Line conduct rainwater harvesting as an environmental protection measure . It is also the first railway project in the world to earn carbon credits after being registered with the United Nations under the Clean Development Mechanism , and has so far earned 400 @,@ 000 carbon credits by saving energy through the use of regenerative braking systems on its trains . To reduce its dependence on non @-@ renewable sources of energy , DMRC is looking forward to harness solar energy and install solar panels at the Karkardooma , Noida Sector @-@ 21 , Anand Vihar and Pragati Maidan Metro stations and DMRC 's residential complex at Pushp Vihar . 
