The recent car-free Sunday, on September 21st, once again proved that air quality is improving and noise pollution is decreasing, especially along Brussels’ busiest roads. The sound pressure dropped by 99 percent compared to a regular Sunday.
The measuring stations on the E40 in Sint-Lambrechts-Woluwe and the E411 in Oudergem recorded sound pressure levels of 50 and 44 dB(A) on car-free Sunday. On a typical Sunday, that figure is 67 decibels. At other locations, the noise level was 3.2 to 8 decibels lower, representing a decrease of 50 to 84%.
Air quality
Air quality was also noticeably better. The concentration of nitrogen monoxide (NO), a gas emitted from car exhausts, among other sources, dropped by 80 to even 96 percent compared to an average Sunday.
According to the Flemish Environment Agency (VMM), road traffic is a key source of NOₓ and other pollution. In Brussels, the Airscan organization measured that NO₂ concentrations on a car-free day even met WHO guideline values, which is usually not the case.
Proven improvement
In 2024, 52 Belgian cities and municipalities, together representing approximately 3.6 million inhabitants, organized a car-free Sunday. In 2025, Antwerp, Ghent, Leuven, Mechelen, Bruges, Kortrijk, Ostend, Hasselt, Turnhout, Roeselare, and dozens of other municipalities participated.
European studies have shown that on such days, there is often a measurable decrease in concentrations of NO, NO₂, and particulate matter (PM2.5), depending on how busy the roads are.
Livability
A European overview – “Air quality mitigation in European cities: Status and outcomes in ten European cities” – indicated that low-emission zones (LEZs) and car-free measures in cities such as Antwerp, Madrid, and Paris led to significant improvements in air quality.
Several Belgian cities, including Antwerp, Bruges, Leuven, and Hasselt, among others, are organizing car-free days as part of European Mobility Week. Ghent’s city center has mainly been car-free since 2017. This has resulted in fewer cars in the city center, more bicycle and pedestrian traffic, and a more pleasant living environment.
