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.
Yup I live in an area built around the time 'roundabout fever' has gripped urban planners, so there's quite a few around. To add a few of my personal complaints:
- When there's a low traffic lane merging with a high traffic one, it's either impossible to enter, and you have to wait forever, or there's a traffic light cleverly hidden a couple hundred meters away, as to not break the illusion
- They do work in the middle of nowhere merging two low traffic roads. However for every roundabout you have to slow down which breaks the flow of traffic, and consumes more gas. There's often a string of 5-6 of these things.
- Having to turn to even go straight makes me queasy. Not too bad if there's just 1, but can be super uncomfortable when there's a string of them (which is common)
- 2 lane roundabouts are crazy dangerous and confusing (which is the same). You might understand how they work, but the car behind you might not. Besides due to the geometry of the whole thing, you have to cut across diagonally to car traffic to get to the inner lane.
- There's another kind of 2 lane roundabout, which is less dangerous, but only allows you to turn right from the outer lane. If you're unfamiliar with which kind you're facing, you might be in for a detour. Even if you know, there's often a fight to merge into the inner lane, which is not exactly pleasant or safe.
I guess roundabouts are a niche solution that can work sometimes, but there's a whole internet cult for them, composed mostly of people who don't really live in an area with roundabouts.
> there's a whole internet cult for them, composed mostly of people who don't really live in an area with roundabouts.
Alternatively: it's people who do live in areas which have a lot of them - and well-designed ones at that. Most of your issues boil down to "people aren't familiar with them", which automatically solves itself over time.
There is no such thing as a "roundabout fever", just like there isn't a "traffic light fever". To any halfway-competent engineer, they are just one tool among many.
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.
torginus · · focus · HN ↗
- When there's a low traffic lane merging with a high traffic one, it's either impossible to enter, and you have to wait forever, or there's a traffic light cleverly hidden a couple hundred meters away, as to not break the illusion
- They do work in the middle of nowhere merging two low traffic roads. However for every roundabout you have to slow down which breaks the flow of traffic, and consumes more gas. There's often a string of 5-6 of these things.
- Having to turn to even go straight makes me queasy. Not too bad if there's just 1, but can be super uncomfortable when there's a string of them (which is common)
- 2 lane roundabouts are crazy dangerous and confusing (which is the same). You might understand how they work, but the car behind you might not. Besides due to the geometry of the whole thing, you have to cut across diagonally to car traffic to get to the inner lane.
- There's another kind of 2 lane roundabout, which is less dangerous, but only allows you to turn right from the outer lane. If you're unfamiliar with which kind you're facing, you might be in for a detour. Even if you know, there's often a fight to merge into the inner lane, which is not exactly pleasant or safe.
I guess roundabouts are a niche solution that can work sometimes, but there's a whole internet cult for them, composed mostly of people who don't really live in an area with roundabouts.
crote · · focus · HN ↗
Alternatively: it's people who do live in areas which have a lot of them - and well-designed ones at that. Most of your issues boil down to "people aren't familiar with them", which automatically solves itself over time.
There is no such thing as a "roundabout fever", just like there isn't a "traffic light fever". To any halfway-competent engineer, they are just one tool among many.