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Vehicle type and Pollutant Emission

Vehicle pollution is the introduction of harmful material into the environment by motor vehicles and has become a major source of pollution in many areas.

The health risks of air pollution are extremely serious. Poor air quality increases respiratory ailments like asthma and bronchitis, heightens the risk of life-threatening conditions like cancer, and burdens our health care system with substantial medical costs. Particulate matter is singlehandedly responsible for up to 30,000 premature deaths each year.

The ingredients of air pollution

Cars and trucks produce air pollution throughout their life, including pollution emitted during vehicle operation, refueling, manufacturing, and disposal. Additional emissions are associated with the refining and distribution of vehicle fuel.

These materials, known as pollutants, have several bad effects on human health and the ecosystem.Traffic pollution causes a significant increase in carbon monoxide (CO), carbon dioxide (CO2), volatile organic compounds (VOCs) or hydrocarbons (HCs), nitrogen oxides (NOx), and particulate matter (PM).

Increasing duration of road congestion is leading to an increase in the emission levels, which in turn increases pollution and degrade the air quality.

Introduction to the study

In the present analysis, we have used COPERT model (Computation Of Pollutant Emission from Road Transport) to determine the contribution to emission by vehicle type (2W: Two-Wheelers, HDV: Heavy Duty Vehicles, LDV: Light Duty Vehicles, PC: Passenger Cars) in different running conditions.

The following analyses were done for CO (Carbon monoxide), the most hazardous pollutant.

Two stroke Engine vs Four Stroke Engine Emission level

First, let’s have a look at the difference in the emission levels of a two-stroke engine vehicle and a four-stroke vehicle. Below is the plot of Emission in gram/vehicle/km for two-stroke vs four-stroke two-wheelers, at several speeds.

At lower speed, vehicle emissions are higher which is an established fact. The four-stroke engine emits 50% less pollutant which further decreases to 20% as compared to the two-stroke engine. For both the kind of engines, the emission decreases with an increase in speed in the given range, but the emissions are overall more in case of the two-stroke engine. 

In India, 78% of all registered vehicles are two-wheelers which are all two-stroke engines.

Comparison of emission by different vehicle type

Using COPERT model, we estimated the emission levels of different vehicle types at different speeds: HDV (slope 0, load 100%), IDV (diesel), PC (gasoline 4 stroke), 2W (gasoline 2 stroke)

The biggest culprits in spreading pollutions are the heavy-duty vehicles and two-wheelers. Given the fact that 78% of all registered vehicle in India are two-wheelers,  they are the major source of pollutant emissions.

Emission from Vehicle compliance with Euro -3 and Euro – 4

Next, we calculated emission level by vehicles compliance with euro -3 and euro – 4 at various speeds.

For Heavy Duty Vehicle (HDV), expected emission reduction is 50% by moving from euro-3 to euro-4 standard. For light-duty vehicle (LDV) similar reduction is not so significant but almost 70% reduction is expected in the personal vehicle (PC) segment.


  • This analysis had been done for different vehicle type and their pollution impact. As mentioned above as well, congestion can increase the pollution levels as high congestion level cause reduce traffic flow.
  • All vehicle types emit 2X more pollutant at a lower speed than the higher speed. Two wheelers are a major source of emission and some kind of regulation  is certainly required to curb pollution via them
  • Euro – 4 compliant vehicles emit 50% less pollutant compared to euro-3 compliant vehicles.
  • An initiative should be taken by the authorities to reduce euro – 3 compliant vehicles and move all the vehicles to euro-4 complaints or higher will further help reduce air pollution in the urban area.

The above basic analysis of vehicle type and the emission standards can give us an idea and lay the foundation for building sophisticated pollution models for the upcoming cities.



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