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.
I think to an American, a roundabout is this thing that only works for cars and don't take pedestrians or bicyclists into account, with no paths or crosswalks or anything, so hence "Worse for pedestrians". I don't blame them, both roundabouts and care for pedestrians seems uncommon over there, so of course their experience will point towards roundabouts being worse overall.
(UK experience) If you're trying to cross the road leading onto one, it's much harder to tell if a vehicle is going to hit you at speed. I often observe people turning quickly, without indicating, and had I chosen to cross at that time, there would have been some kind of accident. Junctions tend to not have this problem since cars turning out of them are usually going much slower.
I will say 2 lanes roundabouts as a cyclist are a little intimidating when you need to take the inside lane. Drivers are not looking for cyclists the way they look for cars or will rush to get ahead of you or just try to bully you out of the way by entering the roundabout across you illegally and daring you to take the right of way. At particularly busy examples I will dismount and take the pedestrian crossing.
Junctions have their own problems though: Usually drivers will not permit a cyclist to merge in front of them while traffic is not stopped, which means if the stream of traffic is continuous you need to plan your lane change when traffic is stopped by lights.
As a pedestrian, roundabouts with islands (aka all roundabouts here) are vastly superior.
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.
kawsper · · focus · HN ↗
embedding-shape · · focus · HN ↗
oneeyedpigeon · · focus · HN ↗
Macha · · focus · HN ↗
Junctions have their own problems though: Usually drivers will not permit a cyclist to merge in front of them while traffic is not stopped, which means if the stream of traffic is continuous you need to plan your lane change when traffic is stopped by lights.
As a pedestrian, roundabouts with islands (aka all roundabouts here) are vastly superior.