Hundreds of towns and cities are closing some of their busiest streets to cars for one day to discourage people from driving.
Car-free day is part of a week-long EU campaign to promote more environmentally friendly forms of transport.
Now in its seventh year, European mobility week has been a big hit from the start. The latest campaign is expected to draw even larger crowds because of the surge in fuel prices and growing concern over climate change. The idea is also catching on in other parts of the world. Seoul, Tokyo and Montreal will be joining in this time.
The theme this year is clean air. Cars and lorries create much of the air pollution in urban areas. This is a serious health threat – exhaust fumes have been linked to a whole range of illnesses.
From 16-22 September, events will be held to inform people about the harmful effects of car fumes. Many cities will use the opportunity to introduce new or improved public transport services, pedestrian zones and bike lanes.
The French city of Marseilles will be assessing the air quality at a nursery school and a social centre near a busy motorway. Air samples will be collected and analysed over several weeks and the results announced during mobility week.
In many cities, the highlight of mobility week is the car-free day, when private vehicles are banned from some of the busiest streets. This is a rare chance for walkers and cyclists to have free run of streets that would normally be clogged with traffic.
Banishing cars for a day doesn't only reduce air pollution. Previous campaigns have focused on safer streets for children, improved urban access, and reducing greenhouse gas emissions.