Honk if You Know Why Delhi’s Air Is So Bad

Honk if You Know Why Delhi’s Air Is So Bad By Anupreeta Das Videos by Ahmer Khan Video editing by Jiwoong Hong Oct. 31, 2026 Share full article Every winter, India’s capital is blanketed with toxic smog. Breathing it in is like smoking roughly a dozen cigarettes a day. A major culprit: its notorious traffic. Nearly nine million motorcycles, scooters, auto-rickshaws, private cars, taxis, trucks and buses crowd the city’s roads. Most run on fossil fuels.

A new “winter action plan” restricts certain polluting vehicles from entering the city, but experts say it does not address the root of the problem. Apart from the latest restrictions, which took effect on Sunday, the government has taken other steps to curb emissions. It has previously introduced fuel emission limits and deregistered old vehicles in Delhi. Diesel vehicles older than 10 years were banned, as were gasoline vehicles older than 15 years.

As of March 2026, it had deregistered 6.6 million vehicles. But perhaps millions more vehicles plying the streets of Delhi are either over age or not registered in the city. The new rules, which are in effect only until the worst of the winter pollution is over, will address the problem partially. But experts say that they will not change the broader issues underlying Delhi’s air pollution, among them inadequate public transit and poor transportation planning.

Regulating emissions is complicated by the sheer variety of vehicles on Delhi’s roads, which fall into more than a dozen categories. These vehicles release a mix of harmful pollutants, including PM2.5, tiny particles that can penetrate deep into the lungs and pose serious health risks. On any given day, excavator trucks share the road with three-wheelers hauling furniture, while delivery drivers weave through a maze of cars and the occasional stray animal.

The single biggest category of vehicle is the two-wheeler, popular with millions of lower-income workers. Private cars and jeeps make up the second-biggest category. Car purchases increase as disposable income goes up, and the lack of public transit adds to their appeal. Commercial vehicles like trucks and buses make up more than 5 percent of Delhi’s traffic. There are also around 95,000 three-wheelers, most used as taxis or to transport goods.

Delhi does have a metro system, but it covers the city only partially, making it tough for residents to depend entirely on trains. The city has roughly 6,000 public buses that run on natural gas or electricity, but it needs at least double that number to meet demand. At the same time, electric vehicles only make up 5 percent of all the vehicles in the city. The lack of charging infrastructure and slow government action have held back the adoption of electric vehicles in Delhi.

It’s hard to find them on the streets. In this sped-up three-minute traffic video, there are only seven electric vehicles — identifiable by their green license plates. With Delhi’s roadways unable to handle so many vehicles, traffic jams are common, making the air pollution even worse. Congestion is a big contributor to tailpipe emissions, experts say. When engines are idling or drivers are pressing the brakes frequently because of slow-moving or stationary traffic, fuel burns less efficiently — and more pollutants are released into the air.

At one intersection in central Delhi one recent rush-hour morning, more than a mile of vehicles came to a halt every time there was a red light. The build-up began almost at the dot of 9 a.m, most of it made up by private cars and passenger vehicles like Ubers. By 9:10, we counted hundreds of cars waiting for the light to change. But that was only as far as the eye could see. By 9:40 a.m., a gray haze began to form over the intersection.

My chest and throat started to burn within an hour of exposure to the polluted air. There are several chokepoints in the city where multiple roads merge onto highways that cannot accommodate the traffic volume, or where narrow entrance and exit ramps create bottlenecks. Vehicle exhaust can turn into something even more dangerous. Burning gasoline and diesel produces gases like nitrous oxides, which can react with other chemicals in the air to increase the amount of PM 2.5.

While it’s a problem year round, it becomes much more severe every winter, when the PM 2.5 level in Delhi can regularly rise to more than 10 to 20 times the World Health Organization’s daily recommended limit. Delhi winters are cold, windless and dry, which leaves the ground colder than the air above. A phenomenon known as “temperature inversion” keeps pollution trapped over the city like a blanket. Delhi’s topography also makes matters worse.

The city sits in a bowl-shaped valley, stuck between the Himalayas to the north and a range of hills to the southwest. Things ease a bit by February, when the city starts to get spring showers and more wind. But that doesn’t fix Delhi’s pollution problem, only reduces the urgency of addressing it.