The mayor of London is seeking powers to limit the number of ride-hailing vehicles and private-hire drivers operating in the city, the Guardian reports.

Sadiq Khan considers the cap necessary to combat the city’s ongoing traffic congestion, pollution, and issues of low driver wages.

Last week, New York City became the first major U.S. city to place regulations on ride-hailing services by signing a one-year moratorium on licensing for all new drivers — effectively capping the number of drivers in the city and also setting a minimum wage for app-based drivers.

Mayor Khan, however, lacks the legal right to impose such restrictions, according to the news source.

The number of licenses for private hire drivers in London has almost doubled since the rise of ride-hailing services like Uber and its competitors, from 59,000 in 2009-10 to 114,000 in 2017-18 — with 45,000 of those drivers working for Uber.

Uber recently had its London private hire license revoked after city officials believed its operations were not “fit and proper.” The company ultimately appealed the city’s decision and was granted a 15-month renewal license in June.

In a statement following the release of Mayor Khan’s letter to London Transport Secretary Chris Grayling, Uber addressed concerns of pollution and congestion, but did not directly respond to the mayor’s calls for a driver minimum wage.

“Already more than half of the miles traveled with Uber are in hybrid or electric vehicles. By competing with private cars, getting more people into fewer vehicles and investing in our Clean Air Plan, we can be a part of solution in London.”