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India will move up to the toughest emission standards of BS-VI from the current BS-IV from 2020, skipping an intermediate level, BS V.

BS-VI standards prescribe emission norms that are “fuel-neutral”. At BS-VI levels, the gap between emissions from diesel and petrol vehicles narrows. At that level, emissions will become nearly fuel-neutral.

The Auto Fuel Policy had earlier recommended implementation of BS-VI norms by 2024. Now the Ministry of Road Transport and Highways (MoRTH) has advanced the date to 1 April 2020. Thus, the implementation of the BS-VI is to take place from 2020 itself.

Considering the environmental impact, rising pollution levels and health hazards due to vehicular pollution, the Ministry took the view that the country should switch over directly from BS-IV to BS-VI fuel standards.

What are BS norms?

In vehicles, emissions depend on fuel and emission control technology that are regulated through emission standards.

The BS — or Bharat Stage — emission standards are norms instituted by the government to regulate the output of air pollutants from internal combustion engine equipment, including motor vehicles. India has been following the European (Euro) emission norms, though with a time lag of five years. BS-IV norms are currently applicable in 50 cities in which the required grade of fuel is available; the rest of India still conforms to BS-III standards. From April 01, 2017, the entire nation will move to BS-IV emission norms.

A brief history

  • India introduced emission norms first in 1991, and tightened them in 1996, when most vehicle manufacturers had to incorporate technology upgrades like catalytic converters to cut exhaust emissions.
  • Following the landmark Supreme Court order of April 1999, the Centre, in the year 2000, notified Bharat Stage-I Stage-II norms, broadly equivalent to Euro I and Euro II respectively. BS-II was for the NCR and other metros; BS-I for the rest of India.
  • In April 2010, Bharat Stage IV emission standards were put in place in 13 major cities.
  • India currently follows Bharat Stage-IV norms, but only across 50 major cities. The whole country is scheduled to switch to BS-IV by April 01, 2017.

Emission norms for passenger cars
Norms CO( g/km) HC+ NOx(g/km)
1991 Norms 14.3-27.1 2.0(Only HC)
1996 Norms 8.68-12.40 3.00-4.36
1998 Norms 4.34-6.20 1.50-2.18
India stage 2000 norms 2.72 0.97
Bharat stage-II 2.2 0.5
Bharat Stage-III 2.3 0.35 (combined)
Bharat Stage-IV 1.0 0.18 (combined)


  • CO emissions are Carbon Monoxide emissions are more evident in Petrol engines. Long Term exposure can prevent oxygen transfer and increase headaches/nausea.
  • HC emissions are Hydrocarbons which are again more prevalent in Petrol engines. Short term exposure can cause headaches, vomiting and disorientation.
  • NOx emissions are Nitrogen Oxide emissions which are more prevalent in Diesel engines. Long Term exposure can cause Nose and eye irritation and damage lung tissue.
  • PM is Particulate matter, again more prevalent in a Diesel engine. Long Term exposure can harm the respiratory tract and reduce lung function.
Diesel fuel and vehicular pollution

For years, India subsidized the price of diesel. As the price difference between diesel and petrol widened, many customers started opting for cars with diesel engines. Companies invested in diesel engine capacities. In 2012-13, diesel cars and SUVs accounted for 47% of all vehicles sold.

The government eventually stopped subsidizing diesel. In the year ended 31 March, only 37% of cars and SUVs sold ran on diesel.

That number is likely to see a further decline as concerns over vehicular pollution increase. The Supreme Court recently said no new diesel vehicle with an engine capacity of 2000cc or above could be registered in Delhi, where the air quality has become the worst in the world.

What needs to be done for switching to BS-VI

Benefits of the decision of switching to BS-VI
  1. By switching to BS-VI, India will join the league of the US, Japan and the European Union, which follow Euro Stage VI emission norms. BS-VI is the Indian equivalent of Euro Stage VI.
  2. The jump will make a huge impact and significantly bring down share of vehicular pollution in the overall air pollution of the country. According to a study released by CSE, air pollution claims at least 10,000-30,000 lives a year in Delhi. It is one of the top 10 killers in the world and the fifth leading cause of death in India, said the study titled Body Burden 2015: State of India’s Health.
  3. At the BS-VI level, the gap maintained between emissions from diesel and petrol, wherein diesel cars are allowed to emit more particulate matter and nitrogen oxide, narrows. For instance, in diesel cars, the jump to BS-VI norms will result in reduction of nitrogen oxide emission by 68% and particulate matter, which has a damaging effect on air quality and human health, by 82%. Similarly, in heavy-duty vehicles like trucks, the shift to BS-VI norms would result in reduction of nitrogen oxide emissions by 87% and particulate matter by 67%.
Problems associated with the decision
  1. The decision will make cars, sports utility vehicles (SUVs), trucks and buses more expensive. Moving to BS-VI directly will require significant technological upgrades and auto companies may have to invest Rs.40,000-60,000 crore to do so. The move will increase the price of cars in India substantially.
  2. Automakers have clearly said that going to BS-VI directly would leave them with not enough time to design changes in their vehicles, considering that two critical components — diesel particulate filter and selective catalytic reduction module — would have to be adapted to India’s peculiar conditions, where running speeds are much lower than in Europe or the US.
  3. For this upgrade, vehicles must be fitted with DPF (diesel particulate filter), a cylindrical object mounted vertically inside the engine compartment. In India, where small cars are preferred, fitting DPF in the limited bonnet space would involve major design and re-engineering work. Bonnet length may have to be increased, which would make vehicles longer than 4 metres, and attract more excise duty under existing norms.
  4. DPF would have to be optimised for Indian conditions. The technology available in Europe cannot be used in plug-and-play mode. Low driving speeds in India would make it difficult to achieve temperatures of 600 degrees Celsius required to burn the soot in DPF, and equipment manufacturers would have to work with temperatures of 400 degrees in sight.
  5. Motorcycle and scooter makers—they outnumber cars 6 to 1 —have been spared. Most follow BS-III emission standards.
  6. There is a supply issue and it is unlikely that BS-VI fuel will be available across the country. Currently, only 50 cities in India get BS-IV fuel, while the rest still use BS-III fuel. The government has been unable to move completely to BS-IV because refiners have been unable to produce the superior fuel in the required quantities. BS-IV petrol and diesel essentially contains less sulphur, a major air pollutant. Sulphur also lowers the efficiency of catalytic converters, which control emissions.
  7. Bosch Ltd, the world’s largest manufacturer of fuel injection systems and engine technologies, has warned the government that such a move can lead to safety and quality problems. Bosch wrote in a letter dated 5 June, 2015 that it would take as much as four-and-a-half years of lead time for design, application and validation of new engine technologies to move from BS-IV to BS-V, and a similar time to graduate to BS-VI. In this technology, usually, diesel is injected to increase temperatures so that temperature of 600 degrees Celsius is obtained to burn the soot. But the accumulation of excess fuel in the compartment can cause a fire. The injection rate has to be optimised and vehicles re-engineered for safety. The integrity of the vehicle too has to be considered. This would require validation tests over 600,000-700,000 km — a process that may take up to four years.
  8. At every stage, the technology is getting more complex. To attain the specified super low emissions, all reactions have to be precise, and controlled by microprocessors. If BS-V were to be skipped entirely, then both DPF and SCR would need to be fitted together for testing, which, auto firms say, would make it extremely difficult to detect which of the technologies is at fault in case of errors in the system. Ideally, the technologies must be introduced in series, and then synergised.