India: Heavy-duty: Emissions

India: Heavy-duty: Emissions


Bharat Stage (BS) VI standards (based on Euro VI) standards applied to all new vehicles nationwide in April 2020. This transition to BS VI standards also sets the precedent for in-use emissions standards and monitoring in the form of OBD standards and requirements in heavy duty vehicles. 

Standard type
Conventional pollutant emission limits

Regulatory Body
The body primarily responsible for setting emissions and efficiency standards is the Ministry of Road Transport and Highways (MoRTH). Further detail regarding India’s regulatory bodies can be found on the India Regulatory Background page. Other regulatory agencies responsible for fuel and environmental regulations are:

Vehicles with Gross Vehicle Weight (GVW) > 3,500 kg including commercial trucks, buses, and on-road vocational vehicles such as refuse haulers and cement mixers


Starting with court rulings in the late 1980s and 1990s, India began to lower its permissible vehicular pollution emission limits for four-wheelers. Beginning in 2000, India followed the ‘Euro’ pathway, adopting parallel ‘Bharat’ standards (i.e., Bharat III standards are equivalent to Euro III standards).

Important legislative milestones include:

The Auto Fuel Policy of 2003 also laid out two different sets of standards, one for advanced cities and one for the rest of the country. In the case of heavy-duty vehicles, this incongruity resulted in few trucks meeting the tougher emissions standards of advanced cities, since they were sold and registered in outside areas.

Bharat Stage VI

In April 2020, BS VI emissions standards went into effect nationwide for all light- and heavy-duty vehicles and two- and three-wheelers. Reductions to mass emissions standards, type approval requirements, and on-board diagnostic (OBD) system requirements and durability levels for each vehicle category were implemented. OBD standards were implemented in two phases: Phase-I went into effect in April 2020 and Phase-II is scheduled to go into effect for vehicles manufactured starting in April 2023 and beyond. Testing for real-world emissions in the form for in-service conformity tests (ISC) are also included in the current BS VI scope and are set to go into effect in April 2023. Other provisions for type approval under BS VI standards include the adoption of more stringent WHSC and WHTC test cycles, and off-cycle emissions testing requirements.

Technical Standards

Emission Standards

Prior to 2010, emissions were tested using the ECE R49 test cycle. After 2010, for Bharat III and IV, the ESC and ETC test cycles were used. BS VI requires the application of WHSC and WHTC test cycles. Standards for new heavy-duty engines are listed below.

Emission standards for heavy-duty vehicles and engines
Year Reference Test CO HC CH4 NOx PM PN
g/kWh #/kWh
1992 ECE R49 17.3-32.6 2.7-3.7
1996 ECE R49 11.20 2.40 14.4
2000 Bharat Stage I ECE R49 4.5 1.1 8.0 0.36a
2005b Bharat Stage IIc ECE R49 4.0 1.1 7.0 0.15
2010 Bharat Stage IIId ESC 2.1 0.66 5.0 0.10/0.13f
ETC 5.45 0.78 5.0 0.16/0.221f
2010 Bharat Stage IVe ESC 1.5 0.46 3.5 0.02
ETC 4.0 0.55 3.5 0.03
2020 Bharat Stage VI WHSC(CI) 1.5 0.13 0.40 0.01 8×1011
WHTC(CI) 4.0 0.16 0.46 0.01 6×1011
WHTC(PI) 4.0 0.16g 0.5 0.46 0.01 6×1011
a 0.612 for engines below 85 kW.
b Test cycle changes from ECE R49 to ESC & ETC.
c From 2001 in Delhi, Mumbai, Kolkata and Chennai; 2003 in Bangalore, Hyderabad, Ahmedabad, Pune, Surat, Kanpur and Agra; and 2005 in the rest of the country.
d From 2005 in Delhi, Mumbai, Kolkata, Chennai, Bangalore, Hyderabad, Ahmedabad, Pune, Surat, Kanpur, Solapur, Lucknow, and Agra; and 2010 in the rest of the country.
e From 2010 in Delhi, Mumbai, Kolkata, Chennai, Bangalore, Hyderabad, Ahmedabad, Pune, Surat, Kanpur, Solapur, Lucknow, and Agra. From 2016, applicable in 10 states, different districts & cities in the states of Rajasthan, Maharashtra, Gujarat and Uttar Pradesh and in 4 Union Territories. Nationwide implementation in 2017.
f For engines with swept vol. < 0.75 liter per cylinder and rated power speed > 3000 rpm.
g NMHC for PI engines.

The BS VI standard also includes a limit for ammonia emissions, which should not exceed 10 ppm for compression ignition as well as positive ignition engines.


Heavy-duty vehicle emissions are certified in two phases. First, the engine (including the emission control system) is tested on an engine dynamometer. The vehicle impacts are then incorporated by reference, which requires using other test data and engineering judgment to establish how the remainder of the vehicle’s components would impact engine emissions. Engine emission limits are specified in grams per kilowatt-hour.

BS VI regulations replaced the European Stationary Cycle (ESC) and the European Transient Cycle (ETC) with World Harmonized Steady-State Cycle (WHSC), World Harmonized Transient Cycle (WHTC), respectively. In addition to that, off-cycle emissions limits were set and are tested using World Harmonized Not-to-Exceed (WNTE) cycle. Specifications for PEMS demonstration testing at type approval are also included in the BS VI regulation. Specific procedures regarding these requirements are defined in the AIS 137 standard. Applicability of standards and testing requirements under BS VI regulations can be found here.

OBD Requirements

OBD requirements went into effect under BS VI regulations in April 2020 for all major on-road vehicle categories in India. For heavy-duty vehicles, OBD standards has two stages: BS VI-1 and BS VI-2. BS VI-1 OBD applied to type approvals starting in April 2020, and BS VI-2 OBD applies to all sales and registrations beginning in April 2023. Threshold values for BS VI-1 OBD and BS VI-2 OBD follow preliminary and final Euro VI threshold limits, respectively.

OBD threshold limits, g/kWh
Stage Implementation date Engine category CO NOx PM
BS VI-1 1 Apr 2020 (type approvals)
1 Apr 2021 (all sales)
Compression ignition 1.5 Performance monitoringa
Positive ignition 1.5
BS VI-2 1 Apr 2023 (all sales) Compression ignition 1.2 0.025
Positive ignition 7.5 1.2
a Performance monitoring as per AIS-137 (for wall-flow Diesel Particulate Filter)


BS VI follows Euro VI specifications for the durability of pollution control devices. Manufacturers may either use deterioration factors specified in the standard or evaluate deterioration factors by service accumulation. Minimum service accumulation mileages for different vehicle categories are listed in the following table.

Minimum service accumulation mileages
Vehicle category mileage
N1 and M2 160,000 km
N3 (GVW≤ 16 ton)
M3 (GVW≤ 7.5 ton)
188,000 km
N3 (GVW> 16 ton)
M3 (GVW> 7.5 ton)
233,000 km

Test Fuels

Under Bharat III and IV specifications, fuel used to test emissions from vehicles was cleaner than commercially available fuel. Bharat IV test diesel had a maximum sulfur content of 10 ppm, while commercial diesel contained up to 50 ppm and 350 ppm sulfur in Bharat IV cities and the rest of the country, respectively. The lower sulfur content in test fuel means emissions measurements during testing are lower than real-world emissions on the road, particularly for particulate matter (PM). In an effort to close this gap between real-world emissions and emissions during testing, The Ministry of Petroleum and Natural Gas (MoPNG) announced nationwide supply of BS VI fuel in conjunction with the proposed BS VI emission standard implementation date of 1 April 2020. The BS VI fuel standard has maximum of 10 ppm sulfur in addition to other changes to fuel specifications. For details on fuel specifications for BS VI, see India: Fuels: Diesel and Gasoline. As of April 2020, all commercial fuel supplied nationwide has to compliant with BS VI fuel specification limits which can be found in the ARAI Indian Emission Regulation Booklet, which also includes full diesel and petrol specifications for test fuels.

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