Since we're back to circles...
What made NJ circles death traps for decades is that almost each one had their own local 'rule' about which oncoming traffic had the right-of-way. For, you see, the major route was expected to enter the circle from both directions and the minor 'side' roads were the ones that had to yield to those in the circle.
And there was no signage to indicate that.
Then, as population density grew, the major two-lane roads always had continuous oncoming traffic which prevented the 'side' spurs from entering. And so, for a while, they'd install traffic lights on the main road about 50 yards from the circle just to stop the oncoming traffic so the side roads can get on and through. That's right, a light where there is no cross road just to create gaps in the flow of cars.
Now, most circles have been converted to cross roads with lights (and the ones with five spurs are very complicated over which lanes can proceed with separate green lights for going left or straight at each entrance.). And the ones that exist are all properly signed with regard to who has the right of way.
Circles work very well... when there isn't heavy traffic, and are well-signed.