Cars are stuck in traffic on Jan. 4, the fourth day of the odd-even pollution reduction scheme for vehicles in New Delhi. (Harish Tyagi/European Pressphoto Agency)

The High Court in India’s capital said Monday that it would not stop the city’s ­alternate-day driving trial, giving a boost to the 15-day program that officials hope will curb some of the worst urban air pollution in the world.

The court had reviewed several public-interest petitions that had challenged the program, which, since Jan. 1, has limited drivers to odd or even days depending on their license plate number.

Officials have said the odd-even plan has brought down pollution levels during peak hours and removed more than 1 million cars a day from the capital’s normally jammed roads.

New Delhi, which is home to 6 million people and 8 million vehicles, has the worst air of any major city in the world, according to a 2014 World Health Organization study.

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The Delhi transport and rural development minister, Gopal Rai, praised the court’s decision, saying it would help the children of the city — who are increasingly suffering respiratory ailments — to breathe freely.

Delhi residents have carpooled, crammed themselves into crowded buses and dusted off scooters they haven’t used for years in an effort to do their civic duty — and avoid a $30 fine. About 6,000 citations have been issued so far.

During restricted travel times — 8 a.m. to 8 p.m., excluding Sundays — traffic flowed as freely as on a holiday, while buses and Metro trains were full at some points during rush hour. Commuters complained that the city’s auto-rickshaw and taxi drivers were price-gouging.

“We have a terrible time commuting. It has become a nightmare,” said Delhi resident Suraj Sharma, 24, who was trying to get to her job at a school. “Metro is not convenient on my route. And you have to wait for buses, and these days they have become so crowded. Auto-rickshaws overcharge, and now you can’t even trust Uber, because most of the time they show surge prices.”

Critics questioned whether the Delhi government’s plan is improving the city’s air, a foul-smelling haze of construction dust, vehicle exhaust, industrial output and smoke.

Harish Salve, a lawyer for the Delhi government, said in court that data — backed by research by the Center for Science and Environment — showed that pollution diminished during peak hours during the trial’s first week.

Yet many experts doubted that statement.

The data journalism site ­IndiaSpend installed air-quality monitors throughout the city and found that air pollution levels rose 50 percent between the last week of December and the first week of January, although it noted that temperature, wind speed and increased moisture could account for the rise.

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At 7 a.m. Monday, the monitor at the U.S. Embassy registered an air-quality index of 318, a “very unhealthy” level, according to the U.S. Environmental Protection Agency, which rates anything below 50 as “good.” Delhi’s off-the-charts air pollution prompted the embassy to add a new color to its ranking last week — black. That’s for air beyond a “hazardous” index of 500.

The odd-even plan was announced in a chaotic rush in December, before most of the details had been worked out.

The Delhi government later issued a lengthy list of people who would be exempt from the restrictions, including single women drivers and those with scooters.

On the program’s first day, when volunteers handed out ­roses to first-time violators instead of tickets, Chief Minister Arvind Kejriwal tweeted hopeful lyrics from John Lennon’s “Imagine.”

The government increased Metro service and added buses to its fleet of about 5,000, some of which were commandeered from local schools. Children have been kept out of school for the duration of the trial period.

Air-quality experts said it would be weeks before the results could be fully analyzed.

Farheen Fatima contributed to this report.