NEW DELHI (AP) — The New Delhi government on Friday began a second round of a two-week car restriction to reduce air pollution that has made the Indian capital the world's most polluted city.

The city's top elected official Arvind Kejriwal said private cars will be allowed on the streets on alternate days from Friday until April 30 based on even or odd license plate numbers.

Friday was a holiday in India and traffic was a trickle compared to the usual gridlock that swamps the roads in the capital every day. Schools, colleges and government offices were shut.

Residents said the impact of the traffic limitations would be evident only on Monday when people return to work.

Similar restrictions in January had led to a significant reduction in pollution levels after more than one-third of the city's 3 million private cars went off the roads.

Many vehicles, especially trucks, run on highly polluting diesel. The air quality worsens during the winter months, when the combination of ash from crop waste burned in nearby farming areas, construction dust and the still wintry air all contribute to make it difficult to breathe.

On Friday, while the skies were clear, fewer vehicles on the road meant traffic moved smoothly across the city.

Emergency and police vehicles, ambulances, taxis, women drivers and two-wheelers are exempt. The Delhi government had last year ordered all taxis to convert their engines to compressed natural gas by March 31 this year. That date has been extended by a couple more weeks, officials said.

Traffic police and inspectors will be helped by more than 5,000 civil defense volunteers to enforce the two-week rule. Violators will be fined $30.

The World Health Organization said last year that the Indian capital had the worst air quality in the world in 2014, surpassing Beijing.