Why do we need to slow down and even stop cars if we in your proposal even have a dedicated bike lane? Why not put up a small barrier between cars and bikes and

Why do we need to slow down and even stop cars if we in your proposal even have a dedicated bike lane? Why not put up a small barrier between cars and bikes and have everyone go their own way? Speed limits on the US already are insanely slow compared to most of Europe and the bike thing seems to work better their regardless. We need more diverse infrastructure for different modes of transportation. I want trains that go 200mp/h, dedicated bike routes, and smaller dedicated roads for cars that are better organized with much higher speed limits and walkable city centers where pedestrians can feel safe from cars AND bicyclists. Sounds crazy but works in parts of Europe.