The survey was carried out on 407 stations
Visakhapatnam railway station is the cleanest, followed by the one in Secunderabad, among the 75 busiest stations.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/visakhapatnam-railway-station-cleanest-darbhanga-dirtiest-survey
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/business-standard-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rail-transport
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/vishakhapatnam-t
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sanitation
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/darbhanga-t
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/toilets
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/bihar