Over the past two decades, Delhi has served as a primary testing ground for vehicle emission interventions in India. Yet, despite major technology upgrades, internal combustion engine (ICE) vehicles continue to dominate local urban air pollution. Addressing toxic exposures and meeting ambient clean air standards requires a policy transition from incremental ICE clean-ups toward zero-tailpipe-emission mandates and targets.
This is evident from the nature of energy transition in the transport sector. An analysis carried out by Delhi-based Centre for Science and Environment based on the VAHAN database for vehicles and energy data from Petroleum Planning and Analysis Cell of the Union Ministry of Petroleum and Natural Gas, Delhi’s transport energy landscape has undergone a dramatic shift, driven by stringent regulatory measures curtailing dieselisation across the capital. Between 2012-13 and 2025-26, overall diesel vehicle registrations in Delhi dropped by 72 per cent, led by sharp declines in diesel cabs (96 per cent), goods carriers (78 per cent), and personal cars (71 per cent).
This policy-driven contraction altered the city’s transport energy portfolio. Diesel’s share of total transport energy plummeted from a peak of 55 per cent in 2016-17 down to just 15 per cent by 2025-26. Cleaner fuels like CNG expanded their dominance—highlighted during 2018-19’s peak overall transport energy consumption when CNG held a 57 per cent share compared to petrol and diesel at 29 per cent each—firmly demoting diesel from its once-dominant position in Delhi’s mobility ecosystem.
Transport energy transition in Delhi: Reduced and avoided use of transport diesel
This change in Delhi was propelled by a comprehensive sequence of legal mandates and judicial directives implemented between 1998 and 2023. A 1998 Supreme Court directive mandated the conversion of all public transport—including buses, autorickshaws, and taxis—to CNG. The city then enforced rapid leapfrogging of fuel and vehicle standards, moving from Bharat Stage (BS) I in 1999 to BS II in 2000, skipping intermediate timelines to reach BS VI nationwide by April 1, 2020, and BS VI Stage 2 Real Driving Emissions regulations by 2023.
This was possible because of economic disincentives for diesel. Environmental Compensation Charges were levied on heavy trucks entering Delhi, alongside Environmental Pollution Charges on large diesel cars and SUVs, while an Air Ambience Charge was added directly to local diesel sales. To further control the fleet, authorities instituted a complete ban on 10-year-old diesel vehicles and 15-year-old petrol vehicles and constructed peripheral expressways to bypass non-destined truck traffic around the capital.
Despite these multi-stage interventions, which reduced per-vehicle particulate matter standards by over 90-95 per cent from BS I to BS VI, ambient air quality targets remain unmet due to fleet volume expansion. Source apportionment studies in Delhi analysed by the Commission for Air Quality Management (CAQM) show that vehicles remain the largest local contributor to PM2.5 in Delhi. Seasonal trends show that vehicles account for 19-24 per cent (averaging 23 per cent) of total PM2.5 in winter and 18-21 per cent (averaging 19 per cent) in summer. A detailed breakdown of local pollution sources within Delhi during peak pollution episodes reveal that Delhi transport contributes half of all local particulate emissions sources, far outstripping all other sectors.
Delhi: Trend in annual PM2.5 levels; Bending of the pollution curve – yet the challenge remains
Thus, Delhi shows that incremental clean-ups of combustion technologies cannot deliver the public health protections required to meet ambient air quality benchmarks.
Against this backdrop, the Delhi Electric Vehicle Policy marks a shift away from earlier fuel-switching approaches toward ambitious, target-driven fleet electrification. By prioritising high-utilisation segments—including public buses, two- and three-wheelers, delivery fleets, and ride-hailing aggregators—the Delhi model focuses directly on eliminating local urban pollution exposure where commuters are most vulnerable.
Delhi’s experience proves that simply upgrading combustion engines—even with advanced pollution controls—cannot fully solve urban air pollution. Across India, adding roughly 3 million new vehicles every year cancels out the gains made by cleaner individual engines. Also, research on short-lived climate pollutants like black carbon shows that while modern BS VI and Euro 6 filters reduce total particle weight, problems like unburnt fuel, cold engine starts, and real-world wear and tear keep pollution at dangerous levels. To prevent toxic exposure in crowded cities that need a 30 to 70 per cent drop in air pollution, we need absolute zero tailpipe emissions—which only battery electric or pure zero-emission engines can deliver.
Making this shift requires clear goals, yet India’s official rules currently differ from global zero-emission benchmarks. The California Air Resources Board and the European Union limit the zero-emission tag to technologies with no internal combustion engine at all, such as battery electric and hydrogen fuel cell vehicles. Similarly, China categorises regular non-plug-in hybrids as fuel-efficient cars rather than zero-emission vehicles.
In contrast, NITI Aayog’s framework groups intermediate technologies based on lifecycle technologies—like flex-fuel vehicles using high ethanol blends, compressed biogas vehicles, and regular hybrids—under the same category as pure battery electric vehicles (EVs).
This mixed definition lets intermediate combustion engines access the subsidies, tax breaks, and fuel efficiency super-credits meant for pure EVs. As a result, carmakers feel less pressure to invest heavily in pure EV designs, local battery manufacturing, and dedicated zero-emission supply chains.
To achieve a rapid transition across the country, India must move away from short-term subsidies toward enforceable legal rules, while fixing big operational hurdles. As consumer subsidy programs like PM e-DRIVE face budget cuts, long-term growth depends on unused policy tools—specifically binding sales targets for manufacturers and strict supply-side rules.
At the same time, policies must fix rules that weaken these goals. For example, CAFE III fuel economy standards are currently diluted by extra credits given to hybrids and biofuel vehicles, while environmental laws remain under enforced. Crucially, India must scale up areas that are lagging behind, including local battery production under the Advanced Chemistry Cell scheme, reliable charging stations in cities and along highway freight routes, and specialised green loans for commercial fleets.
Therefore, an aggressive roadmap built on ten strategic actions must replace reliance on subsidies. This starts with enforcing manufacturer sales quotas, tightening CAFE norms, setting binding state targets, and mandating electric vehicle purchases for public fleets and ride-hailing companies.
The next steps include de-risking electric bus contracts, opening up easy financing for two- and three-wheelers, setting binding goals for delivery fleets, and electrifying busy freight corridors with targeted electric truck support. Alongside these steps, guaranteeing public charging access, creating a local battery recycling industry, and removing bank lending barriers will clear remaining operational challenges.
Executing this combined plan is essential to build guaranteed, long-term demand for electric vehicles and battery cells. In turn, this steady demand will ensure the market buys the vehicles and batteries currently supported by government Production Linked Incentive (PLI) schemes.
Aligning national policies with a strict, tailpipe-focused zero-emission framework remains essential to securing both long-term energy independence and clean air.