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.
My main two cons with roundabouts are that one, when you have those residential streets where basically every intersection is a roundabout so you get many of them in a quick sequence when you’re going straight all that centripetal force is annoying to deal with.
And the second thing is when you have very large roundabouts, there’s always a bit of chaos involved between shifting lanes from the innermost lane towards the outermost lane because I’ve noticed people don’t enter the roundabout on the right lane, so there’s always a little bit of chaos during the crossover.
> when you’re going straight all that centripetal force is annoying to deal with.
I have literally never noticed this. Are you perhaps speeding through them, instead of properly slowing down?
> there’s always a bit of chaos involved between shifting lanes from the innermost lane towards the outermost lane because I’ve noticed people don’t enter the roundabout on the right lane, so there’s always a little bit of chaos during the crossover.
Multi-lane roundabouts are a completely different beast, and shouldn't be used until both the engineers and the population have gotten plenty of experience with regular one-lane roundabouts. Two-lane ones are just about doable with hard lane separation, but anything more is asking for trouble.
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.
dyauspitr · · focus · HN ↗
And the second thing is when you have very large roundabouts, there’s always a bit of chaos involved between shifting lanes from the innermost lane towards the outermost lane because I’ve noticed people don’t enter the roundabout on the right lane, so there’s always a little bit of chaos during the crossover.
crote · · focus · HN ↗
I have literally never noticed this. Are you perhaps speeding through them, instead of properly slowing down?
> there’s always a bit of chaos involved between shifting lanes from the innermost lane towards the outermost lane because I’ve noticed people don’t enter the roundabout on the right lane, so there’s always a little bit of chaos during the crossover.
Multi-lane roundabouts are a completely different beast, and shouldn't be used until both the engineers and the population have gotten plenty of experience with regular one-lane roundabouts. Two-lane ones are just about doable with hard lane separation, but anything more is asking for trouble.