Bharat stage emission standards (BSES) are emission standards instituted by the Government of India to regulate the output of air pollutants from compression ignition engines and Spark-ignition engines equipment, including motor vehicles. The standards and the timeline for implementation are set by the Central Pollution Control Board under the Ministry of Environment, Forest and Climate Change.^[1]

The standards, based on European regulations were first introduced in 2000. Progressively stringent norms have been rolled out since then. All new vehicles manufactured after the implementation of the norms have to be compliant with the regulations.^[2] Since October 2010, Bharat Stage (BS) III norms have been enforced across the country. In 13 major cities, Bharat Stage IV emission norms have been in place since April 2010^[3] and it has been enforced for entire country since April 2017. In 2016, the Indian government announced that the country would skip the BS V norms altogether and adopt BS VI norms by 2020.^[4] In its recent judgment, the Supreme Court has banned the sale and registration of motor vehicles conforming to the emission standard Bharat Stage IV in the entire country from 1 April 2020.^[5]

On 15 November 2017, the Petroleum Ministry of India, in consultation with public oil marketing companies, decided to bring forward the date of BS VI grade auto fuels in NCT of Delhi with effect from 1 April 2018 instead of 1 April 2020. In fact, Petroleum Ministry OMCs were asked to examine the possibility of introduction of BS VI auto fuels in the whole of NCR area from 1 April 2019. This huge step was taken due to the heavy problem of air pollution faced by Delhi which became worse around 2019. The decision was met with disarray by the automobile companies as they had planned the development according to roadmap for 2020.

The phasing out of 2-stroke engine for two wheelers, the cessation of production of the Maruti 800, and the introduction of electronic controls have been due to the regulations related to vehicular emissions.^[6]

While the norms help in bringing down pollution levels, it invariably results in increased vehicle cost due to the improved technology and higher fuel prices. However, this increase in private cost is offset by savings in health costs for the public, as there is a lesser amount of disease-causing particulate matter and pollution in the air. Exposure to air pollution can lead to respiratory and cardiovascular diseases, which is estimated to be the cause for 6,20,000 early deaths in 2010, and the health cost of air pollution in India has been assessed at 3% of its GDP.^{[citation needed]}

To regulate the pollution emitted by cars and two-wheelers, the Government of India has placed forth regulations known as Bharat Stage Emission Standards (BSES). The Central Government has mandated that every vehicle manufacturer, both two-wheels and four-wheels, ought to manufacture, sell and register solely BS6 (BSVI) vehicles from 1 April 2020.

Both BSIV and BSVI area unit emission norms that set the most permissible levels for pollutants emitting from an automotive or a two-wheeler exhaust. Compared to the BS4, BS6 emission standards area unit stricter, whereas makers use this variation to update their vehicles with new options and safety standards, the largest or the numerous modification comes within the type of stricter permissible emission norms.^[7]

The below table offers Associate in Nursing insight into the modification within the permissible emission levels of BS6 vehicles compared to BS4 vehicles:

These area unit emission standards set by Bharat Safety Emission commonplace (BSEB) to manage the output of pollutants from vehicles plying on the road. The Central Pollution Control Board, under the Ministry of Environment, Forest and Climate Change (Mo.E.F.C.C.), sets the permissible pollution levels and timeline to implement an equivalent by vehicle makers.

The abbreviation of Bharat Stage is 'BS' suffixed with the iteration of the stage of emission norms, similar to how European emissions standards are named. The initial BSI (BS1) standard was first introduced in mid 1999, with the second and third iteration first introduced in mid 2000 and 2005 named BSII (BS2) and BSIII (BS3), respectively.

The fourth iteration BSIV or BS4 was introduced in 2017, and therefore the delay between the introduction of BS3 and BS4 resulted in the fast-tracking of the BSVI or BS6 standards by skipping the BSV (BS5) norms. Each of the regulations have stricter emission standards compared to its predecessors.

The first emission norms were introduced in India in 1991 for petroleum distillate, and 1992 for diesel vehicles. These were followed by making the Catalytic converter mandatory for petrol vehicles and the introduction of unleaded petrol in the market.^[8]

On 29 April 1999, the Supreme Court of India ruled that all vehicles in India have to meet Euro I or India 2000 norms by 1 June 1999 and Euro II will be imperative in the NCR by 1 April 2000. Car makers were not prepared for this transition and in a subsequent judgement the implementation date for Euro II was not enforced.^[9][10]

In 2002, the Indian Government accepted the report submitted by the Mashelkar committee. The committee proposed a road map for the roll-out of Euro based emission norms for India. It also recommended a phased implementation of future norms with the regulations being implemented in major cities first and extended to the rest of the country after a few years.^[11]

Based on the recommendations of the committee, the National Auto Fuel policy was announced officially in 2003. The roadmap for implementation of the Bharat stage norms were laid out until 2010. The policy also created guidelines for auto fuels, reduction of pollution from older vehicles and R&D for air quality data creation and health administration.^[12]

The above standards apply to all new 4-wheeled vehicles sold and registered in the respective regions. In addition, the National Auto Fuel Policy introduces certain emission requirements for interstate buses with routes originating or terminating in Delhi or the other 10 cities.

Progress of emission standards for 2-and 3-wheeled vehicles:^[14]

In order to comply with the BSIV norms, 2- and 3-wheeler manufacturers will have to fit an evaporative emission control unit, which should lower the amount of fuel that is evaporated when the motorcycle is parked.

Emission standards for new heavy-duty diesel engines—applicable to vehicles of GVW > 3,500 kg—are listed in Table 3.

More details on Euro I–III regulations can be found in the EU heavy-duty engine standards.

Emission standards for light-duty diesel vehicles (GVW ≤ 3,500 kg) are summarised in Table 4. Ranges of emission limits refer to different classes (by reference mass) of light commercial vehicles; comparable to EU light-duty vehicle emission standards. The lowest limit in each range applies to passenger cars (GVW ≤ 2,500 kg; up to 6 seats).

The test cycle has been the ECE + EUDC for low power vehicles (with maximum speed limited to 90 km/h). Before 2000, emissions were measured over an Indian test cycle.

Engines for use in light-duty vehicles can be also emission tested using an engine dynamo-meter. The respective emission standards are listed in Table 5.

Emissions standards for petrol vehicles (GVW ≤ 3,500 kg) are summarised in Table 6. Ranges of emission limits refer to different classes of light commercial vehicles (comparable to EU light-duty vehicle emission standards). The lowest limit in each range applies to passenger cars (GVW ≤ 2,500 kg; up to 6 seats).

Petrol vehicles must also meet an evaporative (SHED) limit of 2 g/test (effective 2000).

Emission standards for 2- and 3-wheeled petrol vehicles are listed in the following tables.^[16]

• 1991 – Idle CO limits for petrol vehicles and free acceleration smoke for diesel vehicles, mass emission norms for petrol vehicles.
• 1992 – Mass emission norms for diesel vehicles.
• 1996 – Revision of mass emission norms for petrol and diesel vehicles, mandatory fitment of catalytic converter for cars in metros on unleaded petrol.
• 1998 – Cold start norms introduced.
• 2000 – India 2000 (equivalent to Euro I) norms, modified IDC (Indian driving cycle), Bharat Stage II norms for Delhi.
• 2001 – Bharat Stage II (equivalent to Euro II) norms for all metros, emission norms for CNG and LPG vehicles.
• 2003 – Bharat Stage II (equivalent to Euro II) norms for 13 major cities.
• 2005 – From 1 April, Bharat Stage IV (equivalent to Euro IV^{[citation needed]}) norms for 13 major cities.
• 2010 – Bharat Stage IV emission norms for 2-wheelers, 3-wheelers and 4-wheelers for the entire country, whereas Bharat Stage IV (equivalent to Euro IV) for 13 major cities for only 4-wheelers. Bharat Stage IV also has norms on OBD (similar to Euro III but diluted).
• 2017 – Bharat Stage IV norms for all vehicles.
• 2018 - Bharat Stage VI fuel norms from 1 April 2018 in Delhi instead of 2020.^[17]
• 2020 – Bharat Stage VI fuel norms from 1 April 2020 nationwide switching India to world's cleanest diesel and petrol.^[18]
• 2023 - Bharat Stage VI Second Phase Fuel norms from 1 April 2023 have only Petrol also called RDE norms with e20 fuels.

India's auto sector accounts for about 18% of the total CO₂ emissions in the country. Relative CO₂ emissions from transport have risen rapidly in recent years, but like the EU, currently there are no standards for CO₂ emission limits for pollution from vehicles.

As per Bharat Stage-6 norms, the emission of carbon monoxide is to be reduced by 30% and NO_x by 80%. The BS-6 norms also sets limits for Hydrocarbon and particulate emissions, which were not specified in earlier norms. To meet the emission requirements of Bharat Stage-6, the carburetors in petrol engines need to be replaced by the programmed fuel injectors. To further reduce tail pipe emissions, the exhaust system would be fitted with three way catalytic converters. The norms also mandates On-Board Diagnostic System (OBD) for all BS-6 compliant vehicles.^[19]

As per the Bharat Stage-6 norms, the NO_x emissions from a diesel engines are to be reduced by 70% and particulates by 80%. To achieve this, the engines need to be equipped with Euro-6 compliant technologies. The major technical changes to associated with this are:

1. Fitting diesel particulate filters in exhaust system.
2. Using Selective Catalytic Reduction (SCR) or Exhaust Gas Recirculation techniques to reduce NO_x in emissions.
3. An on-board diagnostic system required to monitor the malfunctioning of parts related to emissions^[20]

There is also no provision to make the CO₂ emissions labelling mandatory on cars in the country. A system exists in the EU to ensure that information relating to the fuel economy and CO₂ emissions of new passenger cars offered for sale or lease in the Community is made available to consumers to enable consumers to make an informed choice.

Emission standards for diesel construction machinery were adopted on 21 September 2006. The standards are structured into two tiers:

• Bharat (CEV) Stage II—These standards are based on the EU Stage I requirements, but also cover smaller engines that were not regulated under the EU Stage I.
• Bharat (CEV) Stage III—These standards are based on US Tier 2/3 requirements.

The standards are summarised in the following table:

The limit values apply for both type approval (TA) and conformity of production (COP) testing. Testing is performed on an engine dynamo-meter over the ISO 8178 C1 (8-mode) and D2 (5-mode) test cycles. The Bharat Stage III standards must be met over the useful life periods shown in Table 11. Alternatively, manufacturers may use fixed emission deterioration factors of 1.1 for CO, 1.05 for HC, 1.05 for NO_x, and 1.1 for PM.

Emission standards for diesel agricultural tractors are summarised in Table 12.

Emissions are tested over the ISO 8178 C1 (8-mode) cycle. For Bharat (Trem) Stage III A, the useful life periods and deterioration factors are the same as for Bharat (CEV) Stage III, Table 11.

Emissions from new diesel engines used in generator sets have been regulated by the Ministry of Environment and Forests, Government of India [GSR 371 (E), 17 May 2002]. The regulations impose type approval certification, production conformity testing and labelling requirements. Certification agencies include the Automotive Research Association of India (ARAI) and the Vehicle Research and Development Establishment (VRDE). The emission standards are listed below.

Engines are tested over the 5-mode ISO 8178 D2 test cycle. Smoke opacity is measured at full load.

Concentrations are corrected to dry exhaust conditions with 15% residual O₂.

The emission standards for thermal power plants in India are being enforced based on Environment (Protection) Act, 1986 of Government of India and its amendments from time to time.^[21] A summary of emission norms for coal- and gas-based thermal power plants is given in Tables 15 and 16.

The norm for 500 MW and above coal-based power plant being practised is 40 to 50 mg/N⋅m and space is provided in the plant layout for super thermal power stations for installation of flue gas desulfurisation (FGD) system. But FGD is not installed, as it is not required for low sulphur Indian coals while considering SO_x emission from individual chimney.

In addition to the above emission standards, the selection of a site for a new power plant has to maintain the local ambient air quality as given in Table 17.

However the norms for SO_x are even stricter for selection of sites for World Bank funded projects (refer Table 18). For example, if SO_x level is higher than 100 μg/m³, no project with further SO_x emission can be set up; if SO_x level is 100 μg/m³, it is called polluted area and maximum emission from a project should not exceed 100 t/day; and if SO_x is less than 50 μg/m³, it is called unpolluted area, but the SO_x emission from a project should not exceed 500 t/day. The stipulation for NO_x emission is that its emission should not exceed 260 g of NO_x/GJ of heat input.

In view of the above, it may be seen that improved environment norms are linked to financing and are being enforced by international financial institutions and not by the policies/laws of land.

Fuel quality plays a very important role in meeting the stringent emission regulation.

The fuel specifications of petrol and diesel have been aligned with the Corresponding European Fuel Specifications for meeting the Euro II, Euro III and Euro IV emission norms.

The BS IV grade fuel was introduced in 2010 and is available in 39 cities, as reported in 2016. The rest of the country has to make do with BS III fuel.^[22]

The use of alternative fuels has been promoted in India both for energy security and emission reduction. Delhi and Mumbai have more than 100,000 commercial vehicles running on CNG fuel. Delhi has the largest number of CNG commercial vehicles running anywhere in the World. India is planning to introduce Bio-diesel, ethanol petrol blends in a phased manner and has drawn up a road map for the same. The Indian auto industry is working with the authorities to facilitate for introduction of the alternative fuels. India has also set up a task force for preparing the Hydrogen road map. The use of LPG has also been introduced as an auto fuel and the oil industry has drawn up plans for setting up of auto LPG dispensing stations in major cities.

Presently, all vehicles need to undergo a periodic emission check (3 months/ 6 months/ 1 year) at PUC centres, fuel stations and private garages which are authorized to check the vehicles. In addition, transport vehicles need to undergo an annual fitness check carried out by RTOs for emissions, safety and road-worthiness.

The objective of reducing pollution is not achieved to a large extent by the present system. Some reasons for this are:

• Independent centers do not follow rigorous procedures due to inadequate training
• Equipment not subjected to periodic calibration by independent authority
• Lack of professionalism has led to malpractice
• Tracking system of vehicles failing to meet norms non-existent
• The Parivahan website (under MoRTH) for testing petrol/LPG/CNG vehicles does not have the CO-corrected formula specified by ARAI. Due to this deliberate omission by MoRTH, many vehicles with high CO emissions pass the pollution check

The Bharat stage norms have been styled to suit specific needs and demands of Indian conditions. The differences lie essentially in environmental and geographical needs, even though the emission standards are exactly the same.

For instance, Euro III is tested at sub-zero temperatures in European countries. In India, where the average annual temperature ranges between 24 and 28 °C, the test is done away with.

Another major distinction is in the maximum speed at which the vehicle is tested. A speed of 90 km/h is stipulated for BS III, whereas it is 120 km/h for Euro III, keeping emission limits the same in both cases

In addition to limits, test procedure has certain finer points too. For instance, the mass emission test measurements done in g/km on a chassis dynamometer requires a loading of 100 kg weight in addition to unloaded car weight in Europe. In India, BS III norms require an extra loading of 150 kg weight to achieve the desired inertia weight mainly due to road conditions here.^[23]

Various groups and agencies have criticized the government and urged the government of India to draft mandatory fuel efficiency standards for cars in the country, or at least to make the CO₂ emissions labelling mandatory on all new cars in the country. The auto companies should inform the customers about a vehicle's emissions.^[24]

For the emission standards to deliver real emission reductions it is crucial that the test cycles under which the emissions have to comply as much as possible reflect normal driving situations. It was discovered that manufacturers of engine would engage in what was called 'cycle beating' to optimize emission performance to the test cycle, while emissions from typical driving conditions would be much higher than expected, undermining the standards and public health. In one particular instance, research from two German technology institutes found that for diesel cars no 'real' NO_x reductions have been achieved after 13 years of stricter standards.^[25]

In India, the rules and regulations related to driving licenses, registration of motor vehicles, control of traffic, construction and maintenance of motor vehicles, etc. are governed by the Motor Vehicles Act 1988 (MVA) and the Central Motor Vehicles rules 1989 (CMVR). The Ministry of Shipping, Road Transport & Highways (MoSRT&H) acts as a nodal agency for formulation and implementation of various provisions of the Motor Vehicle Act and CMVR.^[26]

To involve all stake holders in regulation formulation, MoSRT&H has constituted two Committees to deliberate and advise Ministry on issues relating to Safety and Emission Regulations, namely –

• CMVR- Technical Standing Committee (CMVR-TSC)
• Standing Committee on Implementation of Emission Legislation (SCOE)

This Committee advises MoSRT&H on various technical aspects related to CMVR. This committee has representatives from various organisations namely; Ministry of Heavy Industries & Public Enterprises (MoHI&PE)), MoSRT&H, Bureau Indian Standards (BIS), Testing Agencies such as Automotive Research Association of India (ARAI), International Centre for Automotive Technology (ICAT - www.icat.in), Vehicle Research Development & Establishment (VRDE), Central Institute of Road Transport (CIRT), industry representatives from Society of Indian Automobile Manufacturers (SIAM), Automotive Component Manufacturers Association (ACMA) and Tractor Manufacturers Association (TMA) and representatives from State Transport Departments. Major functions the committee are:

• To provide technical clarification and interpretation of the Central Motor Vehicles Rules having technical bearing, to MoRT&H, as and when so desired.
• To recommend to the Government the International/ foreign standards which can be used in lieu of standard notified under the CMVR permit use of components/parts/assemblies complying with such standards.
• To make recommendations on any other technical issues which have direct relevance in implementation of the Central Motor Vehicles Rules.
• To make recommendations on the new safety standards of various components for notification and implementation under Central Motor Vehicles Rules.
• To make recommendations on lead time for implementation of such safety standards.
• To recommend amendment of Central Motor Vehicles Rules having technical bearing keeping in view of Changes in automobile technologies.

CMVR-TSC is assisted by another Committee called the Automobile Industry Standards Committee (AISC) having members from various stakeholders in drafting the technical standards related to Safety. The major functions of the committee are as follows:

• Preparation of new standards for automotive items related to safety.
• To review and recommend amendments to the existing standards.
• Recommend adoption of such standards to CMVR Technical Standing Committee
• Recommend commissioning of testing facilities at appropriate stages.
• Recommend the necessary funding of such facilities to the CMVR Technical Standing Committee, and
• Advise CMVR Technical Standing Committee on any other issues referred to it

The National Standards for Automotive Industry are prepared by Bureau of Indian Standards (BIS). The standards formulated by AISC are also converted into Indian Standards by BIS. The standards formulated by both BIS and AISC are considered by CMVR-TSC for implementation.

This Committee deliberates the issues related to implementation of emission regulation. Major functions of this committee are –

• To discuss the future emission norms
• To recommend norms for in-use vehicles to MoSRT&H
• To finalise the test procedures and the implementation strategy for emission norms
• Advise MoSRT&H on any issue relating to implementation of emission regulations.

Based on the recommendations from CMVR-TSC and SCOE, MoSRT&H issues notification for necessary amendments / modifications to the Central Motor Vehicle Rules.

In addition, the other Ministries like Ministry of Environment & Forest (MoEF), Ministry of Petroleum & Natural Gas (MoPNG) and Ministry of Non-conventional Energy Sources are also involved in formulation of regulations relating to Emissions, Noise, Fuels and Alternative Fuel vehicles.

• Air pollution in India
• Automotive Industry Standards
• Regulation on non-exhaust emissions
• Bharat NCAP

• Bansal, Gaurav; Bandivadekar, Anup (2013). "Overview Of India's Vehicle Emissions Control Program - Past Successes And Future Prospects" (PDF). The International Council on Clean Transportation. Retrieved 22 July 2014.