Living in a city which has both hi-tech traffic lights (dynamically selected phases), dumb traffic lights (two alternating phases, one for each direction) and l

Living in a city which has both hi-tech traffic lights (dynamically selected phases), dumb traffic lights (two alternating phases, one for each direction) and low-tech roundabouts (give way on entry), I doubt any of these is a catch-all solution. There are roundabouts which would be better off as traffic lights, uncontrolled intersections where roundabouts would help, and traffic lights which are actively creating problems. For example, I regularly drive across a four-way roundabout; there are strong, almost continuous traffic streams coming from the north and west entrances, exiting mostly east and north. This means that while traffic from the west still mostly manages to merge, traffic from the south is regularly backed up, as there are only a few "slots" left in the roundabout traffic flow where it could merge. This is a spot that would be better served with traffic lights. So, I don't think there's one "The Problem" in traffic engineering, generally solvable.