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.
> Small fender benders and sideswipes are much more frequent
All the sources I can find say roundabouts reduce crashes of all types.
Carmel, IN, America's "roundabout capital" has more than tripled in population while reducing overall traffic accidents / year: <a href="https://eri.iu.edu/erit/case-studies/carmel-indiana-roundabouts.html" rel="nofollow">https://eri.iu.edu/erit/case-studies/carmel-indiana-roundabo....
propter_hoc · · focus · HN ↗
- 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.
allturtles · · focus · HN ↗
All the sources I can find say roundabouts reduce crashes of all types.
Carmel, IN, America's "roundabout capital" has more than tripled in population while reducing overall traffic accidents / year: <a href="https://eri.iu.edu/erit/case-studies/carmel-indiana-roundabouts.html" rel="nofollow">https://eri.iu.edu/erit/case-studies/carmel-indiana-roundabo....