According to data available over 96 lakh vehicles are registered in the state up to April, of which 50 lakh were in Hyderabad.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/hyderabad-bharat-stage-4-yet-make-its-mark
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/deccan-chronicle-telangana
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/telangana
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/hyderabad-t
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/vehicular-pollution
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/bharat-stage-iv
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/vehicle-technology-and-fuel
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution