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Dinesh Mohan, distinguished professor, Shiv Nadar University, and guest professor, Transportation Research and Injury Prevention Programme,discusses the “lack of reliable data in Delhi to calculate sources pollution and its effect.” He argues that “policy makers are announcing “drastic” measures to control pollution without real facts.”

He writes, “…Consider the following: Anyone who attempts to estimate vehicular pollution in Delhi has to rely on assumptions. This is because no one has ever taken a random sampling of various vehicles and measured their emissions while they are on road. So no one knows what CNG buses, taxis or three-wheelers of different ages actually emit while operating at different speeds. All of us are forced to estimate these numbers from new vehicle test results or data from abroad. For example, every chemist knows that NOx is not produced by the fuel used but by Nitrogen and Oxygen in air combining when any fuel burns in an engine. The amount produced increases with increase in temperature of combustion. Diesel engines produce more NOx than petrol engines because diesel burns at a higher temperature than petrol. But, CNG also burns at a much higher temperature than petrol and therefore it is possible that all CNG vehicles produce more NOx, creating more Ozone than petrol cars. But there is no discussion on this issue.”

Mohan believes, “…It is necessary to get studies done for better data on the situation in Delhi. For a start we must have on-road, real-driving emissions tests done using portable emission measurement systems….The best decision taken yet is the move to introduce Bharat VI emission and fuel norms as soon as possible. This will be a major improvement over the present situation. In the meantime, we must start working more seriously on detailed cost-effective studies to ensure various options are available to draw up time-bound programmes with measurable milestones. At this juncture, it is very important to remember M.K. Gandhi’s time-honoured advice: “Action in the absence of knowledge can be dangerous and worse than no action at all”. The Indian Express. Read it on

Delhi’s data deficit