BS VII: India's Chance to Get Transport Emissions Right

India's air quality problems need bold measures

In the 2026 Environmental Performance Index, published by Yale and Columbia universities, India ranked 176th out of 177 countries. The EPI is a composite of many environmental metrics, and its methodology has its critics. But on air quality alone, the picture is no better: India ranks 175th. For anyone familiar with conditions in urban India, the implication is hard to dispute: protecting public health will require substantial and sustained cuts in emissions from every major source, including transport.

For the transport sector, India’s next stage of emission standards, BS VII, is now taking shape, with a final proposal expected in the coming weeks. The technical groundwork is being laid through the Automotive Industry Standards Committee (AISC), which develops the test procedures that underpin India’s Central Motor Vehicle Rules.

On August 19th, the Automotive Research Association of India (ARAI), the Research Institute of the Automotive Industry with the Ministry of Heavy Industries, Govt. of India uploaded the first “D0” draft AIS-215, which defines the test procedures for BS VII. The draft was open for formal comments for a month.

On the topic of evaporative emissions, the leading associations in India and the U.S. have posted an informative technical white paper, and we summarize it here,

A primer on evaporative emissions

Emission debates typically center on tailpipe pollutants – NOx, particulate matter (PM), CO and hydrocarbons – and on how they are measured (laboratory cycles, real-driving emissions, on-board monitoring). Evaporative emissions receive comparatively little attention, even though they are a direct source of volatile organic compounds (VOCs).

Petrol (or gasoline) vapour escapes from a vehicle’s fuel system in several ways: diurnal losses as the fuel tank heats and cools with the daily temperature swing while parked; hot soak losses just after the engine is switched off; running losses during driving; and refuelling losses when vapour is displaced from the tank at the pump.

Modern cars capture most of this vapour in an activated-carbon canister, which is purged back into the engine during driving. If the canister becomes saturated – for example, over several hot days of parking – vapour breaks through to the atmosphere.

These VOCs matter for three reasons: they are precursors to ground-level ozone and secondary PM2.5; they include toxic compounds such as benzene, which IARC classifies as carcinogenic to humans; and every gram lost is fuel the owner has paid for but never uses.

Findings from the MECA–ECMA white paper

In response to the draft proposal, the Manufacturers of Emission Controls Association (MECA) and the Emission Controls Manufacturers Association of India (ECMA) released a white paper, Higher Temperatures, Higher Evaporative Emissions, in September 2026, based on laboratory tests of three petrol cars. Here are the main findings:

Indian summers sit well outside the test window

The current BS6 procedures use a diurnal profile of 20–35 °C that are derived from European regulations. Following European climatic conditions for India hardly makes sense: Indian cities exceed 35 °C on more than 100 days a year, while large EU cities do so on generally less than 5% of days. Ahmedabad, as an example of a populated city, records 53–60 days a year at or above 40 °C. The fuel in the tank can run even hotter than the surrounding air, leading to fuel-tank temperatures to exceed 40 °C.

Emissions rise steeply with temperature

Testing was done on a 2024 BS6 car (1.5 L port-injected engine, 50 L metal tank, 1.0 L canister, E20 certification fuel), preconditioned on the WLTP cycle and tested at ARAI in Pune. Under the certification profile it emitted 1.36 g/test, comfortably within the 2.0 g limit. Under the 25–40 °C profile, however, emissions rose 6.1-fold to 8.35 g; under the 30–45 °C – typical of Indian summers – they rose 39-fold to 53.1 g (Figure 1) – roughly 26 times the 2.0 g limit ! Compare this with tailpipe emissions: a car emitting non-methane hydrocarbons at the BS6 limit of 68 mg/km and driving 33 km a day would emit about 4.5 g over the same two days, making the evaporative emissions at 45 °C about 11 times higher.

Why a 48-hour test? Imagine a vehicle parked for two days, not uncommon in urban households relying on multi-modal transport. The first hot day uses up much of the canister’s capacity, so the second heating cycle produces disproportionately high emissions that a shorter test would miss. As an example, at 25–40 °C, the car was found to emit 0.86 g on the first day and 7.40 g on the second. See the white paper for more details at other temperatures.

Can the problem be solved? Yes, and with existing technology

The Indian car was compared with a 2026 Euro 6e mild hybrid and a 2026 U.S. Tier 3/LEV III car (Table 1). All three were tested with the AIS-175 procedure, certification fuel and a 48-hour diurnal. The U.S. car’s standard canister is about twice the size of the others, to meet the stricter U.S. evaporative requirements.

The U.S. vehicle stayed below 1.0 g/test even at 30–45 °C, equating to a reduction of more than 97% versus the Indian car under the same conditions. The Euro 6e car, with a canister of similar size to the Indian one, emitted far less than the BS6 car (2.05 g versus 8.35 g at 25–40 °C) but still slightly exceeded the 2.0 g limit; it was not tested at 30–45 °C.

Costs, fuel savings and refuelling

According to the analysis cited in the paper, improved evaporative control can be achieved for less than ₹1,400 per light-duty vehicle. And that is more than recovered in savings: the recovered fuel is estimated to save about 4.2 litres of fuel per year, or ₹4,200 over a 10-year life at ₹100/L – enough to offset the hardware cost.

Moreover, the same technology can also address refuelling emissions. India currently relies on station-based vapour recovery systems (VRS), which the Supreme Court has directed at major fuel outlets. The efficiency of these VRS depends on installation, inspection and maintenance and can fall to about 50%, versus about 98% for on-board refuelling vapour recovery (ORVR), which is mandatory on new petrol vehicles in the U.S., China and Brazil.

Recommendation

Certification which does not reflect in-use conditions risks a gap between certified and real-world emissions (remember Dieselgate?). The central recommendation here is that the final BS VII standards should adopt a 48-hour, 25–40 °C diurnal profile for all vehicles running on petrol or petrol blends. The change would not require new test procedures or facilities, reduce harmful emissions, and even lead to fuel savings for consumers which offsets any increased cost of added technology.

What about two-wheelers? After all, India sells about 20 million bikes and scooters each year, far outpacing the sale of cars. Yes, the recommendations also apply to two-wheelers. Two wheelers have smaller fuel tanks, but are much larger in number, and have exposed fuel tanks which lead to higher emissions. A similar study is sorely needed, that can quantify the magnitude of the problem for two wheelers.

Additional reading

·        The D0 BS VII AIS-215 draft proposal

·        MECA–ECMA (2026) – Higher Temperatures, Higher Evaporative Emissions: Why India’s Climate Warrants India-Relevant Evaporative-Emissions Test Conditions

·        Wendling, Z. A., Emerson, J. W., Esty, D. C., de Sherbinin, A., Block, S., et al. (2026). 2026 Environmental Performance Index.  New Haven, CT: Yale Center for Environmental Law & Policy.  epi.yale.edu