Research from the Fraunhofer Institut shows that in Germany, tire wear is the single largest source of microplastics, and it's much larger than the next source which is -- wait for it -- abrasion of plastic from road surfaces.
Sounds like Germans like to burn rubber (except that car tires are no longer ctual rubber but a composite containing lots of plastic).
https://www.celticwater.co.uk/bloghow-does-plastic-get-into-the-ocean-plastic-pollution-from-roads/