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 live in the UK, which has roundabouts, mini roundabouts, double and triple roundabouts, traffic-light controlled roundabouts, and magic roundabouts. They work perfectly fine.
The difference is that traffic flows very differently in the UK to the US. In fact, the way traffic flows in those two countries captures a lot of their cultural differences. In the US, everything needs a grand overarching theory and imposed order, which is why Americans need traffic lights, and why they’re so keen on a very specific set of liberties that allow them to freely live such similar lifestyles. The UK embraces mild chaos and ruthless pragmatism, with everyone finding locally optimal solutions to their own problems, so things like roundabouts fit well with the national mindset.
Try Spanish roundabouts. On the whole, poorly designed, implemented and regulated. On roundabouts with two or more lanes, laws favour those on the outside lane, so everyone takes the outside lane even if they are travelling 3/4 of the way round. As a result drivers who are in a position to take an exit, do not take that exit. In addition, indicators are not used by most drivers, or they simply leave their indicators on all the way round. In addition, it is not allowed to exit a roundabout from the inside lane even on to a two lane exit. In addition many roundabouts have three lanes to enter onto a two lane roundabout, or two into one, etc. No one knows the rules, or follows them, and no one seems to care, from the civil engineers right down to the end users. The only winners are repair shops.
In comparison, UK roundabouts are civilised examples of harmonious intellectual etiquette. Enjoy them.
[source] I learned to drive in Swindon, home of the Magic Roundabout.
I live in the UK, drive occasionally in Spain due to Spanish in-laws, and agree wholeheartedly. I didn't know about the "outside lane has priority" rule though. I'd noticed it happening, but just thought it was a national quirk rather than gaming the system.
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.
cjs_ac · · focus · HN ↗
The difference is that traffic flows very differently in the UK to the US. In fact, the way traffic flows in those two countries captures a lot of their cultural differences. In the US, everything needs a grand overarching theory and imposed order, which is why Americans need traffic lights, and why they’re so keen on a very specific set of liberties that allow them to freely live such similar lifestyles. The UK embraces mild chaos and ruthless pragmatism, with everyone finding locally optimal solutions to their own problems, so things like roundabouts fit well with the national mindset.
jmkd · · focus · HN ↗
In comparison, UK roundabouts are civilised examples of harmonious intellectual etiquette. Enjoy them.
[source] I learned to drive in Swindon, home of the Magic Roundabout.
frereubu · · focus · HN ↗