This always had the taste of being too US-centric anyway. European countries (and I guess the rest of the world as well) has very steep, narrow and weird roads

This always had the taste of being too US-centric anyway. European countries (and I guess the rest of the world as well) has very steep, narrow and weird roads and don't run on neatly organized grids. So it's even harder to achieve then just fencing cars and separating traffic.