NEW DELHI: An international study, testing on-road emissions of passenger cars in India, says a diesel SUV may be emitting 25 to 65 times more oxides of nitrogen (NOx) than a small petrol car. On-road emissions of diesel cars may also be far higher than their emissions under lab certification conditions, it adds.

The study, conducted by International Centre for Automotive Technology (ICAT), an Indian vehicle-testing agency, and International Council on Clean Transportation (ICCT) that had exposed Volkswagen in the US, has tested a BS-IV-compliant 2015 model of Hyndai i20, its diesel variant, and a diesel Mahindra XUV 500.

Centre for Science and Environment (CSE) drew attention on Saturday to 'Laboratory and On-Road Emission Testing of In-use Passenger Vehicles in India' that says NOx emissions from a small Hyundai i20 diesel car is three to six times the BS-IV standard and as much as nine to 12 times its petrol variant's emissions. The petrol variant itself is violating the standard by 0.5-0.7 times.

The on-road emissions from Mahindra XUV is also found to be four-six times higher than the standard. "NOx emissions from Mahindra's XUV diesel SUV are 25 to 65 times higher than the i20 petrol NOx emissions. This means that in terms of NOx emissions, adding one XUV diesel SUV to the city's car fleet is equal to adding 25 to 65 small petrol cars," said a CSE statement, highlighting major public health implications. Diesel exhaust has been graded as class 1 carcinogen by WHO.

The cars were tested first in laboratories and then with portable emission monitoring equipment while being driven in and around Delhi. It has also been found that BS-IV diesel cars emit at least 1,000 times more ultrafine particles than a BS-VI vehicle.

"This study has confirmed what we already know from 'Dieselgate' in Europe. Diesel cars, particularly large diesel SUVs, are much more polluting on road than petrol cars. With BS-VI, controlling on-road emissions from diesel vehicles will be more complex and expensive than petrol vehicles," said Anumita Roychowdhury, head of Centre for Science and Environment's Right to Clean Air Campaign.

"As seen in Europe, it is vulnerable to poor performance on road and to emission cheating. India must adopt tighter test procedures for vehicle certification and implement direct monitoring of actual emissions. Europe has already implemented this system," she added.

The study also finds that the onboard diagnostic system (OBD) in these cars can't detect certain anomalies. For example, in BS-IV vehicles in India, in-cylinder NOx emissions are controlled by cooled exhaust gas recirculation (EGR) system. "The test has found a mechanical failure in EGR in diesel cars that has resulted in three times more emissions than the fixed limit. But OBD couldn't diagnose it," a CSE researcher said.

CSE recommended that India implement testing of real-world driving emissions with portable emission monitors, and control diesel car growth with pricing and taxation policy.

According to Mahindra and Mahindra, its XUV 500 meets the emission requirements set by regulatory authorities. "Indian authorities are defining a real driving emission cycle, monitoring of which will come into effect from April 2020 along with BS-VI norms. Mahindra will comply with legislative norms," said Rajan Wadhera, president of automotive sector business. On steps taken to meet the current standards, Wadhera said, "We already comply with emission norms."

According to Hyundai, its cars adhere to the norms set by Indian regulatory authorities.

- http://timesofindia.indiatimes.com