Last Friday, Madrid’s tough new vehicle emissions controls went into effect, resulting in a drop in traffic by nearly 32 percent in some parts of the city, reports El País. The new rules impose strict restrictions on which vehicles can enter an area of just under two square miles in the city’s downtown. The plan, known as Madrid Central, is an attempt to lower the city’s nitrogen dioxide levels, which have exceeded European limits since 2010 and are thought to cause around 3,000 premature deaths per year, according to one study.

The exact drop in traffic varied between different areas in the zone. One area, San Bernardo, saw a modest reduction of just over 5 percent, while Gran Vía saw the highest reduction of 31.8 percent. Although Reuters reports that traffic continues to be heavy around the perimeter of the zone, El País claims that even there, traffic levels were down by between 1 and 2 percent. The lack of congestion also had benefits for public transport, with bus speeds on one highway increasing by 14 percent.

Air pollution is Europe’s “biggest environmental risk”

The exact vehicles affected by the ban vary depending on their fuel type, year of manufacture, and how they’re used. Petrol and diesel cars registered before 2000 and 2006, respectively, will be restricted, while hybrid vehicles will be allowed to enter the area and park for a maximum of two hours. However, residents living in the controlled area will not be affected by the ban. Petrol and diesel taxis will continued to be allowed in the area until 2022. Electric cars, which produce no emissions, driven by non-residents will also be allowed to freely enter the area. The new rules are expected to impact around 20 percent of the vehicles that currently enter the city center.

Madrid’s plan has been criticized by political opponents and industry representatives who argue that people drive older, more polluting vehicles because they can’t afford to upgrade, and the new rules unfairly penalize lower-income drivers. The president of the Association of Self-employed Lorry Drivers Antonio Villaverde said that the city could experience supply shortages as lorry drivers struggle to purchase new compliant vehicles. Exceptions for residents may also limit the ban’s effectiveness. The opposition conservative Popular Party plans to challenge the new rules in court.

Madrid is not the only European city to explore the use of vehicle bans in the wake of air pollution being called the “biggest environmental risk” to public health in Europe. Athens and Paris will both ban diesel cars from city streets by 2025, while the latter also wants its streets to be filled with only electric cars by 2030. In 2019, London will introduce an “Ultra Low Emissions Zone” that will see most petrol cars produced before 2005 banned along with most diesel cars produced before 2015.