On November 18, Delhi breathed its worst air ever recorded. With the Air Quality Index at 494, the fourth level of the Graded Response Action Plan snapped into place that morning, putting a stop on all construction activity and the entry of trucks into the city.
As the Supreme Court ordered schools to be closed, Delhi government blamed the Centre for failing to control stubble burning, especially in Uttar Pradesh and Haryana.
However, research shows stubble burning is not the main cause of Delhi’s toxic smog. A study found that, averaged out through the year, stubble burning contributed less than 3% to hazardous particulate matter in 2017.
The largest source of air pollution in Delhi is its vehicular load. In 2019, the Council on Energy, Environment and Water, a research organisation, analysed several studies that broke down the contribution of air pollution by source. It found that vehicles on the road contributed anywhere between one-third to two-thirds of Delhi’s toxic air in 2018.
Confirming this, a study this year by the Centre for Science and Environment found that between mid-October and early November, when farmers burnt paddy stalks to prepare their fields for the next crop, only 8% of air pollution in the national capital region came from stubble burning. Nearly two-thirds of the pollution originated locally, with the transport sector contributing more than half of it.
Delhi’s worsening air quality runs parallel to the rise in the number of vehicles on its roads. Between 1990 and 2018, the national capital region saw a five-fold jump in registered vehicles. Delhi surpasses all other Indian cities with 1.18 crore vehicles on the road, over 90% of which are two-wheelers and cars.
Despite research consistently linking Delhi’s air emergency to its vehicle overload, public discussion and policy responses to address the problem have been largely limited. Experts say this needs to change if the national capital wants to breathe clean air.
Vehicular pollution escapes scrutiny partly because of the frequency with which stubble burning is highlighted in the media, said Sarath Guttikunda, founder and director of UrbanEmissions, an open data source on air pollution trends and analysis. This gives the impression that it is the primary source of Delhi’s air pollution and so it appears to receive the most attention in the policy circle as well, he said.
The focus is misplaced, said Abhishek Kar, senior programme lead at the Council on Energy, Environment and Water. He pointed out that in 2023, between October 15 and November 15 when stubble burning was at its peak, the average AQI in Delhi was 300. After the farm fires stopped, the pollution did not clear up during the rest of winter – the average AQI rose to 350.
“It shows that unless we target the major sources like transport, and biomass burning for cooking and heating, we will not significantly improve Delhi’s air quality across the winter season,” Kar added.
It is not that policy makers are not aware of this. Nearly half the measures listed in city plans approved under the National Clean Air Programme are “targeted at the transport sector”, Guttikunda said. This includes strict action against visibly polluting vehicles, introducing early alarm systems related to traffic congestion and promoting battery operated vehicles.
Even the odd-even system put in place in Delhi in previous winters – where private cars could hit the roads only every other day – was based on this understanding. The system did not work because a high number of exclusions were allowed – motorcycles, women-driven cars, those operating on compressed natural gas, among others. “This meant approximately 70% of daytime cars were exempted”, according to a study co-authored by Guttikunda.
But experts say temporarily reducing the number of vehicles on the road cannot solve Delhi’s air crisis. The city needs more drastic solutions – like fewer cars all year round.
Faced with worsening air, Beijing, for instance, introduced a series of caps on private car ownership, ranging from a parking restriction in 1998, a vehicle purchase tax in 2004, and allowing only a limited registration of vehicles through lottery allocation.
In contrast, the Indian government, instead of pursuing policies that limit car ownership and usage, has focused on getting automobile makers to improve emission standards. From 2020, only Bharat Stage VI or BS 6 standard vehicles, which emit lesser pollutants, can be manufactured and sold in India. This has led to some improvements, but a 2024 study found that real world emissions of BS 6 vehicles are higher than the set limits.
In addition, “since the number of vehicles are increasing rapidly, the benefits of controlling emissions are not coming through”, noted Sayan Roy, programme manager for the Sustainable Mobility Programme at the Centre for Science and Environment.
Guttikunda said, “If we can reduce 10% of the car usage, that will be a win bigger than the CNG conversion, in terms of emissions.”
Some argue that weaning away people from personal cars requires better public transport. Delhi has an extensive metro network, but rides are expensive. And the city has only 7,600 buses – 45 buses buses per lakh people, way below the global benchmark of 90 buses per lakh population.
“For public transport, particularly buses, to be successful, three key factors are essential: comfort, punctuality and safety,” said Guttikunda. “However, with the current operating fleet falling significantly short of demand these expectations remain unmet.”
But improvements in public transport “won’t be adequate without strategies to simultaneously restrain personal vehicle usage,” CSE’s Anumita Roychowdhury has argued in the Indian Express. A recent study by the organisation pointed out that vehicle taxation structure in Delhi favours cars over buses. Roychowdhury described this as a “hidden subsidy” for cars.
“Largely free and uncontrolled parking and the absence of effective taxes on car usage and congestion pricing make personal vehicles comparatively cheaper to operate,” she wrote.
This needs to change, she argued. “The political will to tame the car has to get stronger to ensure a substantial shift to public transport.”