Delhi Metro’s popularity has increased since it started running the first stretch between Shahdara and Tis Hazari in December 2002.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/carriage-convenience-0
[2] http://admin.indiaenvironmentportal.org.in/category/author/ankur-paliwal
[3] http://admin.indiaenvironmentportal.org.in/category/author/nidhi-jamwal
[4] http://admin.indiaenvironmentportal.org.in/category/newspaper/down-earth
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi-metro-rail-corporation-dmrc