It's not just ease of commuting that Delhi Metro is offering. According to the Delhi Metro chief, Metro is also contributing to the environment by reducing carbon dioxide emissions.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/metro-steps-solar-power-push-reducing-carbon-footprints
[2] http://admin.indiaenvironmentportal.org.in/category/author/rumu-banerjee
[3] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-new-delhi
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/solar-energy
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi-metro-rail-corporation-dmrc
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/carbon-dioxide
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/renewable-energy
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/energy