Strong correlation of car’s age, mileage on emissions: Study
The analysis found that age and mileage have a higher correlation with increased CO, HC and air-fuel ratio (AFR). In comparison, no direct correlation was seen with older vehicles and the O2 and CO2 emissions the vehicle was releasing.
Emissions from a relatively new car that guzzles fuel will be as high as those from an older car that is more efficient, found a study published in the American Society of Civil Engineering (ACSE)’s Journal of Environmental Engineering, underlining that while a vehicle’s age is a key determinant of its pollution levels, other factors like mileage also play a crucial role.
The study, titled ‘Investigating Exhaust Emissions from In-Use Passenger Cars: Exploratory Analysis and Policy Outlook’, was carried out by researchers from Delhi Technological University (DTU) on 1,580 in-use petrol vehicles over an 18-month span.
It also found that age and mileage have the highest impact on carbon monoxide (CO) concentration and hydrocarbons (HC) in emissions. Authors of the study, as a result, recommend that pollution-under control certifications give more weightage a vehicle’s CO levels.
The analysis found that age and mileage have a higher correlation with increased CO, HC and air-fuel ratio (AFR). In comparison, no direct correlation was seen with older vehicles and the O2 and CO2 emissions the vehicle was releasing.
“While age has been determined as one of the key factors affecting tailpipe parameters, high mileage is the second and emissions are worst at a high combination of both. However, this shows that even if the vehicle is three or four years old, has extremely high mileage and the vehicle is being used to travel several kilometres daily, then emissions can still be as high as an older vehicle that is used less,” said Rajeev Kumar Mishra, the lead author of the study and assistant professor at DTU’s environmental engineering department .
The parameters of the study, he said, assessed the age of the vehicle, mileage, maintenance category, application emission norms and some engine-related parameters. All cars were tested in a laboratory-based environment and not during road-use.
“Out of the 1,580 cars tested, only three were older than 15-years-old,” he said.
Abhinav Pandey, one of the co-authors of the study, said a vehicle’s emissions start to worsen once it is seven to eight-years-old and crosses a mileage of over 100,000km.
“This implies that such cars have more chances of becoming non-compliant to the applicable ‘in-use’ emission norms,” he said, adding that well-maintained cars that were regularly serviced were able to stay within the existing BS IV norms.
Vehicles were split into four groups based on the quality of their upkeep, Pandey said — ‘Very good’, good’, ‘poor’ and ‘unsatisfactory’.
“‘Very good’ or ‘good’ category vehicles easily met the limits, while ‘poor’ maintenance category ones were on the threshold. Vehicles with ‘unsatisfactory’ maintenance had a more apparent effect on tailpipe emissions,” he added.
The study also states the findings should help car manufacturers adopt a suitable strategy for tuning the engine or vehicle before they become non-compliant to emission norms.
“As an essential policy measure, the study recommends that governments and policymakers in developing countries investigate phasing out the old and more polluting cars from the roads, rather than tightening emission norms alone,” the research adds.
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