Advocates also accuse city officials of doling out parking placards as political favors to the powerful teachers’ unions and others, including 50,000 new placards for teachers and school employees in 2017. They said the city has helped create the problem because more placards lead to more opportunities for abuse and the oversupply of placards has encouraged more people to drive to work, putting more cars on the road.

“The elephant in the room is whether they can reduce placard abuse to everyone’s satisfaction without a meaningful reduction in the sheer number of placards,” said Danny Pearlstein, a spokesman for the Riders Alliance, a grass-roots group of transit riders.

The placards, Mr. Pearlstein said, have essentially created a large class of privileged city workers, many of whom would otherwise be taking buses and subways. “It’s a question of fairness,” he said. “Plenty of people have to get to work on time and do work that is important to the life of the city.”

City officials said that 50,000 temporary placards for school employees were issued to resolve a labor dispute with the teachers’ union. But the number of placards dropped to 31,500 later that year when the Education Department moved to an online application system that set out clear eligibility standards. The department has also tightened oversight of placards, including tracking names and vehicle information for every placard in a database and printing permits on paper that cannot be illegally copied.

The previous mayor, Michael R. Bloomberg, challenged the city’s tradition of bestowing parking placards on city employees and in 2008 his administration cut the number in half to 67,297 from 144,048 the year before. Mr. de Blasio’s aides said the number of placards had crept back up to 103,000 by the time he took office in 2014.

Bruce Schaller, a consultant who helped lead the Bloomberg efforts, said any comprehensive effort to curb placard abuse would sputter unless placard numbers were reduced.

Still, Mr. Schaller said he believed the new measures were at least a start. “If there’s real follow-through to what they’re announcing, then people should be able to see improvement,” he said. “Will it completely solve the problem? I can guarantee you no, but New Yorkers are more realistic than that.”