For the average Metro rider, the non-Metro part of the commute -getting to the station and to the final destination after the ride -is just 20% of the total journey distance.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/getting-metro-station-can-cost-more-ride
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/council-scientific-and-industrial-research-csir
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/metro
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/public-transport
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/centre-science-and-environment-cse
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution-control