Did anyone study the fuel efficiency of a roundabout vs. traffic light?
I expect it to be a lot worse.
- roundabout, light traffic : break, turn, accelerate again, 100% of the time
- (dumb) traffic light, light traffic: 50% chance of stopping and accelerating again, 50% chance of not slowing down at all.
- roundabout, heavy traffic : stop, move 3m, stop again, move 3m more, stop again, repeat 10 times, finally turn, accelerate.
- traffic light, heavy traffic: stop & engine off, start & move 100m, stop & engine off, start again and accelerate.
Mythbusters did a test of roundabouts vs fourway intersections (no lights), many years ago.
Their conclusion i believe was they were about the same in pretty much all regards.
It was highly synthetic, people driving around a small course with roundabouts or fourway intersections, continuously for an hour or something.
Streetcraft on Youtube compared 2 similar routes, one with roundabouts and one with traffic lights. They found roundabouts to be quicker and more fuel efficient: https://www.youtube.com/watch?v=012fMI3TdRo
You're missing the variations where you have stop lights to go into the roundabout or the even worse variant, roundabouts that are large enough to have 3-4 zones of stoplights inside of the roundabout itself!
I'll take a roundabout any time of the day, but then I mostly to drive out in the public when the traffic is the least, so any stop lights tend to be more annoying that useful.