Why Roundabouts Are a Software Engineer's Dream
The Beauty of Roundabouts
A software engineer confesses a soft spot for roundabouts, arguing they solve intersection problems with radical simplicity. Unlike traffic lights, which need sensors that miss motorcycles and bicycles and encourage yellow-light racing, roundabouts use no electricity or active control. They also turn leftover land into art, fountains, or welcome signs. The post includes hand-picked examples from a roundabout database.
It's solving all of these problems while being radically simpler. It has no active control mechanism and consumes no electricity. It's just a static structure, sitting there doing nothing.
- propter_hoc
My best friend is a highly experienced civil engineer, specialized in designing intersections. His take on roundabouts:
- They are adored by urban planners because they look nice and you can put a statue or fountain in the middle
- They reduce T-bone collisions
However:
- Small fender benders and sideswipes are much more frequent
- They use way more area
- They work where each direction has an approximately equal amount of traffic. However, usually, one direction (north/south, say) has a larger share of the traffic. In those cases, the bulk of traffic all needs to slow down, downshift, turn a bit in one direction and then turn a bit in the other direction for the minority of traffic that's bleeding on or off the main artery. In those cases, a traffic light is better because the timing can be adjusted to the proportion of traffic from each direction (and more flexible since it can be adjusted over time).
- Finally, they're also (mostly) worse for cyclists and pedestrians.
Essentially, they have use cases, especially in small towns, and they're pretty, but they're usually not the right engineering solution.
- M95D
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.
- herbst
The city I grew up in had no roundabouts back then. Today it does have some, some were even made and removed again since. People there hate roundabouts.
The city I live nearby now has so many roundabouts that I can drive for over an hour without seeing a traffic light. It always had those, people are used to using them.
Guess what works better and barely has any traffic issues at all.
- rusty_rick
This led me down somewhat of a rabbit hole looking at roundabouts, then to the official roundabout page from the Department of Transportation, where I couldn't believe my eyes to see that National Roundabout Week is next week: https://highways.dot.gov/safety/intersection-safety/nrw
- AndrewSwift
One thing the US could do to make traffic lights a lot safer is copy eg France and only show the lights on the near side of the intersection.
In France, if you move up too far, you can no longer see what color the light is — consequently everyone waits back where they should.
In the US, you can edge out into the traffic and still see your light.
- brudgers
[edit: for clarity, I am not against roundabouts]
I don't have real expertise in civil engineering
Traffic lights have a smaller physical footprint and require less construction activity.
Traffic lights fit on a cost spectrum from two stop sighs, to four stop signs, to stop signs plus blinking lights, to non-trivial signaling.
First make it work. Then make it good. Then make it fast.
Engineering is not a one size fits all discipline.
[edit: I have a background in urban planning, architecture, and real-estate development]
- chris_money202
Surprised Carmel, Indiana hasn’t been mentioned in article or comments. They replaced almost every single stoplight and stop sign intersection in the town with roundabouts. Think the number of roundabouts in the town is in the hundreds
- teddyh
> Roundabouts come with this otherwise unused patch of land in the middle. Apparently, it has become common practice around the world to put some random art there, or a little green space, or a fountain, or a "welcome to this town" sign.
Or a dog: <https://en.wikipedia.org/w/index.php?title=Roundabout_dog&ol...>