IIT Bombay Researchers Found One Fifth Of The Heavy Vehicles As Super-emitters

Vehicular emission is one of the major contributors to urban air pollution in India. Rapid urbanization leads to increased congestion on the roads thus resulting in more pollution due to an increase in time spent on the road. Some vehicles release higher amounts of pollutants. A recent study by the IIT Bombay researchers looks into the factors determining the polluting characteristics of such high-emitting vehicles or Super-emitters.

Super-emitters are vehicles that are either old, poorly maintained, or overloaded heavy-duty vehicles. They release a significant amount of pollutants compared to the other vehicles. According to the IIT Bombay study, light-duty vehicles weigh less than 3,500 kg including cars, two-wheelers, three-wheelers, and light commercial goods vehicles. The age of the vehicles and the maintenance of the engine potentially determine whether the vehicle is a super-emitter or not.

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IIT researcher Sohana Debbarma said that no such study was conducted in India earlier. The study aims to reduce uncertainty in the emission estimation of real-world vehicular fleets.

For this study, researchers set up their pollutant-measuring equipment at the entry and exit of the Kamshet-I tunnel located on the Mumbai-Pune Expressway. Both the exhaust emissions and non-exhaust emissions were collected. The traffic data was collected for two weeks, using high-definition video cameras and the vehicle registration number data.

Vehicles were identified as super-emitters through manual inspection based on video surveillance records. Those that emitted a visible plume of smoke were identified as super emitters which were validated using the information about the age of the vehicle, type of emission technology- Bharat Stages (BS) – II, III, and IV and the type of fuel.

The pollutant levels at the exit of the tunnel were significantly higher than those at the entry. While the traffic flow was the major determinant of pollutants at the exit, other surrounding factors influenced the pollutant levels at the entry. As per the researchers, the difference in pollutant levels between the entry and exit helped to effectively capture the impact of the traffic flow.

The IIT Bombay researchers found that super-emitters constituted an average of 21% of the total vehicle fleet in the Kamshet-I tunnel, where 10% of the fleet had a visible plume of smoke and 11% were overloaded vehicles. The team developed a mathematical model to predict the share of super emitters in real-world traffic in India.

Old vehicles with engines that don’t comply with emission technologies and are poorly maintained become potential super-emitters. The vehicle scrapping policy in India aims to scrap private and commercial petrol vehicles 15 years old and diesel vehicles more than 10 years old. Sometimes new vehicles but poorly managed can lead to disproportionate pollution from a significant portion of India.

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The IIT Bombay research highlighted the importance of enforcing strict regulations and inspection and maintenance programs on India’s vehicle fleet for super emitters.  According to the Voluntary Vehicle Fleet Modernisation Program (VVMP) that was published by the Ministry of Road Transport and Highways, vehicles replaced at the end of their lives will reduce vehicular pollution by 15-20%.

“While the exhaust emissions can be controlled with the introduction of EVs, the non-exhaust emissions will still be of concern. There are still no emission standards for non-exhaust emissions in India,” concluded Ms Debbarma.