There are other actors on the road, namely pedestrians and cyclists. Unless we're going to remove the right of citizens to the street at all, they will be present and will need to be accommodated for.
My point is that unless you get rid of them completely, traffic flow is not going to increase. You can't have free-flowing traffic everywhere and also have pedestrians safely crossing the street, and the lower bound on a traffic light cycle today is the amount of time it takes an old person to cross the street from curb to curb.
