I like how everyone skims over the point of where filtering works great in Europe. The problem is a cultural one of dogshit drivers. In most Euro countries to get a permit requires much more serious testing and much higher penalties for dumb screw ups.

Its one of the very few things Im envious of Europe on. Meanwhile back in the US we're are plagued with uninsured trash and a huge number of senior citizens that are well past the point of safely driving.