While high levels of pollution due to increasing number of vehicles is one problem, poor Pollution under Control (PUC) test centres worsen the air.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/puc-test-centres-worsen-air-quality
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/statesman-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/diesel
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/cars
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/pollution-under-control-certification
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/centre-science-and-environment-cse
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-pollution-control-board-cpcb
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/oxides-nitrogen-nox
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/vehicular-pollution
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution