On paper, the city has more than 2.8 million vehicles that are 15 years old and need to be off the roads. But, over the last three months, only 1,110 have been seized by the traffic police.

“It is less than 1% of the total challans for traffic violations issued during the period,” a senior traffic official said.

The National Green Tribunal had in November banned all vehicles older than 15 years — almost a third of the 8.4 million motorbikes, trucks, cars and auto-rickshaws registered — from the streets of Delhi, citing a Supreme Court order of 1997.

“The SC order is the law of the land and it has to be implemented,” NGT chairman Swatanter Kumar said, in a bid to clean up Delhi air that the World Health Organization had in 2104 found to be the world’s dirtiest.

The traffic police officials say implementing the order is not easy as not many aged vehicles were on the roads.

Their efforts to track down such vehicles through transport department, too, didn’t yield much. The department hasn’t digitised records of all vehicles, many of which were registered more than 20 years ago.

It is not even known how many of the 2.8 million vehicles have been sold, scrapped or moved out of Delhi.

Had the transport department updated and authenticated its record, the traffic police could have got in touch with the owners, sources said.

Admitting to the problem, Delhi chief secretary KK Sharma has asked the transport department to launch a website to gather about such vehicles from their owners. “This is the only way out to update the database and start the crackdown,” a transport official said, adding it would take some time.

The delay may force the Delhi government to seek more time from NGT to implement its action plan to fight air pollution.

Vehicular emissions are one of the biggest contributors to air pollution in Delhi, which has the highest numbers of cars in India. On an average, the Capital adds 1,400 cars on its roads every day.