At the call of many environmental groups and associations, thousands of demonstrators rallied against the highway that would connect the cities of Toulouse and Castres.
As part of the demonstration, which started in the city of Saix in Tarn province, protesters are expected to march about 12 kilometers.
Among the demonstrators are opposition politicians such as MPs Anne Stambach-Terrenoir and Sandrine Rousseau.
In their written statement, the organizers argue that 53 kilometers of bitumen will be poured as part of the highway construction, and this will destroy 400 hectares of land suitable for agriculture.
Footage shared on social media shows demonstrators throwing banana peels at the road and building a wall in the middle of the road.
The French channel BFMTV reported that demonstrators set fire to hay bales and car tires in the middle of the road.