Following is the chronology of events in which the National Green Tribunal refused to lift the ban on ten-year-old diesel vehicles in Delhi-NCR:
*November 26, 2014: NGT bans all vehicles - diesel or petrol - over 15-years old from plying in Delhi-NCR.
*April 7, 2015: NGT bans 10-year old diesel vehicles.
*April 27: Government moves NGT seeking stay of its ban orders in Delhi-NCR.
*January 6, 2016: NGT expands ambit of air pollution case to metropolises like Mumbai, Kolkata and Chennai.
*July 18: NGT directs Delhi RTO to ban all diesel vehicles over 10 years old.
*July 20: Deregistration of 15 to 10 years old diesel vehicles in the national capital would be carried out in a phased manner, says NGT.
*October 7: NGT warns of halting state transport in four northern states if they do not introduce CNG.
*August 3, 2017: 'No objection certificate' would not be granted to diesel cars de-registered in Delhi-NCR for plying in other areas if the states concerned do not identify "no-pollution" zones: NGT orders.
*September 14: NGT dismisses Centre's plea seeking modification of its order banning ten-year-old diesel vehicles in Delhi-NCR.
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