The Process of Rating

Vehicular Air Pollutants and Greenhouse Gases: From Origin to Impact

Vehicles engines combust fuel (petrol, diesel, CNG) to generate energy for operating. Upon fuel combustion, the engine partially converts this energy to power the vehicle, and the tailpipes release air pollutants – Carbon Monoxide CO, Hydrocarbons HC, Nitrogen Oxides NOx, Particulate Matter PM – and Greenhouse Gases (GHG) – Carbon Dioxide CO2, Methane CH4, Nitrogen Dioxide N2O. While these emissions and gases are a natural by-product of fuel combustion in vehicles, but inefficiencies in engines and drivetrains, poor driving conditions, type of fuel used and other factors play a decisive role in determining the quantity of each pollutant and GHG released, and whether they are within the safe limits.

These negative impacts impose damages in the form of the acceleration of climate warming, extreme weather impacts, low agricultural yield, depletion of air quality, thick smog, respiratory and heart diseases, and other health impairments that decrease the number of years from a person’s life and increase medical expenditures. GVR considers the human health and environmental (climate change, damage to crops, decline in visibility) damages from vehicle tail pipe releases.

Damage Costs Methodology: Translating Vehicular Impacts in Monetary terms

The Green Vehicle Rating (GVR) uses a ‘Damage costs’ methodology to estimate the costs of negative impacts on the health and environment from tail pipe pollutants and GHGs. These costs are in ₹ per km terms. This methodology follows the principles of the field of environmental economics.

For every unit km that a vehicle moves, it combusts fuel and releases a unit mass of pollutants and GHGs from its tail pipe, which negatively contributes to the environment and human health. The negative impacts from each unit mass of pollutant and GHG released carry a monetary cost that varies by pollutant type, source (transport sector – cars/bikes, trucks) and geographical + demographical features of the city/country (such as population density, value of statistical life, ambient conditions, topography of the region to name a few). These are known as social costs, written in ₹/gm terms. In other words, the social costs for each pollutant and GHG represent the money that will be needed to undo the damages caused by every gram of pollutant released.

For each of the 22 vehicle models: the mass of each pollutant/GHG (gm/km) is multiplied with the social cost for that pollutant/GHG (₹/gm). This gives the damage cost from each pollutant/GHG, all of which are added to find out the total damage cost due to the ail pipe emissions and GHGs of a vehicle. Higher the cost, lower is the rating. Further, the damage cost from each vehicle is added to its commonly understood ‘Total Cost of Ownership’ to calculate the Real-World Cost of Ownership of a vehicle.

Damage cost methods are frequently used in other countries such as Europe and the US for cost and benefit evaluation of environmental regulations. Governments and academic researchers in other countries have estimated the marginal social costs. For GVR, an extensive survey of literature was conducted and a benefit-transfer method was used to find the marginal social costs of pollutants and GHGs from vehicles in India.

For GVR, the unit mass of pollutants and GHGs are sourced from the following sources:

  • Pollutants – mass released gm/km is sourced from Form 22
  • GHG – mass released gm/km is derived from the fuel efficiency as reported by auto dealers /online market places

Five Steps of Rating


  • Mass of air pollutants: Form 22 (NOx, CO, HC, PM)
  • Mass of greenhouse gases: Processed from fuel efficiency nos. (CO2) in gm/km
  • Marginal social costs: of health damage from pollutants, and CO2 impacts in ₹/gm
  • Tech specs and price for 22 vehicles


  • Social Impacts = Health + Environmental Impacts
  • Human Health: diseases (NCDs) and early deaths
  • Environmental: climate change, visibility and damage to crops


  • Impacts of each pollutant and GHG are monetised
  • Eg. Vehicle AB → Health cost of NOx from AB (₹/km) = (Mass of NOx from AB) X (Marginal social costs of NOx)
  • This is done for each vehicle
  • Total negative impact cost = Health cost + Environmental cost → OUTPUT 2 of GVR


  • Normalisation against a ‘Reference Vehicle’
  • Reference vehicle for 2-wheelers – BS VI norms, 100 km/L mileage
  • Reference vehicle for 3-wheelers – BS VI compliant, 40 km/ L
  • This produces dimensionless rating for each vehicle


  • In line with regional priorities, weightage:
  • Health costs = 60%
  • Environmental costs = 40%
  • Vehicle rating score (1 to 10)→ OUTPUT 1 of GVR