After a court order in 2004, Delhi government managed a huge swing away from polluting fuels to the much less polluting compressed natural gas (CNG), at least in vehicular public transport.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/green-advantage-cng-metro-lost-over-years
[2] http://admin.indiaenvironmentportal.org.in/category/author/subodh-varma
[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/oil-pollution
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/cng-buses
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/vehicular-pollution
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/public-transport
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rspm-pm-10
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/industrial-pollution
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/battery-vehicles
[12] http://admin.indiaenvironmentportal.org.in/thesaurus/bus-rapid-transit-system
[13] http://admin.indiaenvironmentportal.org.in/category/thesaurus/inorganic-pollutants
[14] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution
[15] http://admin.indiaenvironmentportal.org.in/category/thesaurus/yamuna
[16] http://admin.indiaenvironmentportal.org.in/category/thesaurus/river-pollution
[17] http://admin.indiaenvironmentportal.org.in/category/thesaurus/common-effluent-treatment-plant-cetp
[18] http://admin.indiaenvironmentportal.org.in/category/thesaurus/biological-oxygen-demand-bod
[19] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution