Emissions of nitrogen oxides (NOx) from adding one diesel SUV to the city’s fleet is equal to emissions from adding 25-65 small petrol cars, a study conducted in the Delhi-NCR region has found. NOx is a harmful gas that adds to the deadly levels of ozone in the air.
“Lab tests of petrol and diesel cars, and SUVs — done in the way similar to vehicle certification — shows NOx emissions from petrol cars are well below the emission standards of BS-IV. However, the NOx emissions are much higher from a diesel car,” the study states.
Further, BS-IV diesel cars emit at least 1,000 times more ultrafine particles than BS-VI vehicles, according to the study. The findings are important given that SUVs are among the fastest growing segments in the passenger vehicle category. Recently, reports claimed that the sale of utility vehicles grew by over 35% in July, after prices were reduced owing to the implementation of GST.
The study, ‘Laboratory and On-Road Emission Testing of in-use Passenger Vehicles in India’, done by the Indian vehicle testing agency, International Centre for Automotive Technology and International Council on Clean Transportation, is one of the first to test for actual emissions from vehicles while being driven on roads.
The study found that real-world NOx emissions from diesel SUVs are 4-6 times higher than its already weak NOx standard, which in turn is five times higher than the petrol NOx standard.
The study also found that the on-board diagnostic (OBD) systems in cars designed to detect a whole range of emission anomalies are not effective. The study notes that OBD in BS-IV diesel cars is unable to detect problems with several aspects of emission control system.
“The main point is that investments are made to improve new emission standards, but if this technology cannot be made to work on roads, it negates the purpose from a public health point of view,” said Centre for Science and Environment’s executive director Anumita Roychowdhury.
“Diesel cars, and particularly large diesel SUVs, are much more polluting on road than petrol cars… India must adopt tighter test procedures for vehicle certification as well as implement direct monitoring of actual emissions while vehicles are being driven on road,” she said.