I'm pretty convinced that self driving cars can fix this. Reaction times will be much faster and they can network together to spread out the braking and acceleration. Possibly even merging at high speed.
A more powerful potential mechanism is that they can be programmed to respect do not enter directives from a traffic control system (keeping human drivers off a freeway would take a lot of infrastructure). So the amount of traffic on the road can be regulated to keep it below the capacity implied by the safe response time of the vehicles.
