Humans could do it too, but there is always this selfish asshole ruining it. We have that exiting Richmond Vancouver area. Everyone is doing 100km/h and there is no congestion ahead, but there is a merge in lane from an alternate route behind, so the asshole sees that as a way to get ahead before the merge in tapers off. So they pull out speed to end of lane, dart in dangerously and have to heavy brake to slow to traffic speed. The reduced space makes the car behind heavy brake and that processes backwards until traffic starts to halt. If asshole had stayed in the flow, there would be no stop on the had highway

Trains also cut congestion.