Madrid’s new mayor has halted the city’s congestion pricing program, despite early evidence that it eased traffic and reduced pollution after going into effect last November. It’s the first major European city to reverse the creation of a low-emissions zone, an idea that has become more popular in recent years as the European Union looks to enforce new clean air regulations across the continent. The move sparked thousands of citizens to protest in the city’s streets this past weekend.

The previous mayor of Madrid installed the low-emissions zone in the downtown area known as Madrid Central late last year. Using security cameras, the city’s government fined offending drivers in high-emissions vehicles 90 euros, or about $102, for entering the zone. Public transportation, residents, some delivery vehicles, and drivers in electric or certified low-emissions cars were exempt.

The returns were immediate. Within one month of launching the program, traffic was cut by an average of around 24 percent, nitrogen oxide (NOx) levels dropped by 38 percent to their lowest point since 2012, and CO2 emissions fell 14 percent, according to The Guardian. At the same time, the drop in congestion increased bus speeds.

But during elections in May, a number of right-wing politicians came to power in the region. Madrid elected a new mayor from Partido Popular, or the People’s Party, named José Luis Martínez-Almeida. He vowed to reverse the low-emissions zone throughout his campaign, arguing that it pushed congestion to the outer parts of the city and hurt businesses in the downtown sector. A leading presidential candidate of the region, who is from the same political party, has said congestion is a part of the “identity of our city,” and that it shows “that the street is always alive.” Madrid’s nightlife “goes hand in hand with traffic jams,” she said.

The European Union’s legislative body has threatened Spain with fines and other penalties if it doesn’t reduce pollution, which is linked to some 30,000 deaths in the country each year, according to a 2015 air quality report from the European Environment Agency. Major European cities have been increasingly adopting various congestion pricing schemes in order to fight pollution problems like Madrid’s, ahead of outright bans on gas and diesel cars. New York City recently became the first city in the US to agree to implement a congestion pricing fix for its traffic and pollution problems.

Martínez-Almeida says he’s only suspending Madrid’s low-emissions zone for three months while he studies “alternative ways” to improve air quality, according to The New York Times. One solution he’s reportedly considering is digging a tunnel to create a passage under the main road that crosses central Madrid.