And yet the average speed of a well-flowing road will invariably be near the speed limit. If your mode of locomotion can't reach the road's ceiling, it shouldn't be on that road.
Only if you can afford to build an extra slow road/lane for them. In the real world, you often can't. In that case, no, slow vehicles should be on that road. They're still people trying to get somewhere just like everyone else. Sometimes they're trucks going uphill - you can't exclude trucks from entire towns. The rule in most places are to pull over from time to time to let following vehicles pass.
