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.
I agree with this, and I'll offer a rationale. Because the US largely "grew up with cars", the economy has been built around the expectation that folks can drive to work. That means everyone needs to be able to drive. If you can't drive, you likely can't work. That isn't the case in the UK, and you'll notice a lot of these "driver beware" analysis is explained by the fact that driving here is more of a privilege than it is a right in the US. This sort of "mild chaos" is prohibitive for a lot of UK drivers, and they just take the bus.
> 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.
Slowing/calming traffic like this is a good thing. Make it impossible to speed. Enforce the existing 35mph speed limit via concrete rather than allowing cars to rip through a yellow light at 70mph. You're also ignoring this aspect when you call roundabouts "(mostly) worse for cyclists and pedestrians".
> 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).
This point is so under-appreciated. Roundabouts are really good in some cases, but they're over-utilized in England. Imagine if the US had roundabouts on the interstate and you're getting close.
I think the main problem in England is that there is just too much traffic for too little road. I don't think there is a simple infrastructure solution to that problem.
For example I was going to point out that roundabout completely fail when one direction becomes nose to tail congested but when I thought about local examples, I'd rather take that over a set of traffic lights where it becomes near impossible to get out from one direction if the traffic keeps backing up onto the junction.
Thank you so much for putting into words what I have feeling but struggling to verbalize. (Boston area, drive for work.)
There is one more downside, they are easy to get lost in, especially in an unfamiliar area. Apple Maps does an OK job guiding me most of the time, but just yesterday I spent an extra 25 minutes going through the same roundabout 3 times before I went the right direction, and each time I had to drive the wrong way, turn around, and then negotiate the same roundabout again.
Not much of America's traffic infrastructure works well. Every month, combined with poorly trained motorists, it contributes to another 9/11's worth of fatalities. The infrastructure you think works, kills enough people for a thirteenth month at the end of every year.
They have their downsides, but "It doesn't work in America" is more informative of American motorists than roundabouts
This led me down somewhat of a rabbit hole looking at roundabouts, then to the official roundabout page from the Department of Transportation, where I couldn't believe my eyes to see that National Roundabout Week is next week: https://highways.dot.gov/safety/intersection-safety/nrw
The city I grew up in had no roundabouts back then. Today it does have some, some were even made and removed again since. People there hate roundabouts.
The city I live nearby now has so many roundabouts that I can drive for over an hour without seeing a traffic light. It always had those, people are used to using them.
Guess what works better and barely has any traffic issues at all.
> Guess what works better and barely has any traffic issues at all.
The one that where mass transit works better.
But yeah, a city still needs cars, and roundabouts are still unbeatable in low-traffic crossings. But they are not the most impacting change a city can make.
As a bicyclist I hate them, at least the smaller ones. Because they slow me down, can't take them with 40 to 50 kph, need to slow down to 30. But that was the intent, yes?
However, crossings with traffic lights I can take at any speed I'm able to, when they are green for me, and I don't need to turn. Or if I can oversee them from afar, and they are empty, and I can give a shit about 'lights'.
The think I don’t like about not being able to “speed” at 50kph(!) through a city is that, at least in Australia with it’s excessive compliment of bureaucratic Karens, is the 30 > 50 > 70 > 60 > 40 > 30 > SCHOOL ZONE > 80 > 40 > 50 > 30 nightmare.
Which does two things, raises state revenue and causes drivers to spend way to much time concentrating on how fast they are going rather than driving to suit the conditions and paying focusing to what’s going on in front of them.
I know of a couple in NSW: one in Albion Park, and another in Bomaderry.
They work well when the peak-hour traffic tends to block some of the entrances. You can use the lights to allow the blocked entrances to flow, then turn the lights off out of peak-hour.
> Roundabouts come with this otherwise unused patch of land in the middle. Apparently, it has become common practice around the world to put some random art there, or a little green space, or a fountain, or a "welcome to this town" sign.
According to Wikipedia, these shrubs are there for a reason. Denmark has found that blocking the line of sight significantly reduces the accident rate by forcing the drivers to slow down and consider only their immediate surroundings. Danish drivers hate them, anyway.
Agreed, it can be really hard to get around a roundabout as a pedestrian if it's not designed for it, and then they make it so both you and people entering don't know each other are there until you're about to get hit.
I've lived some places where 4-way stops were just abused, like Sugarland, TX. England and Ireland are full of roundabouts, some of which are incredibly small, just a painted dot, and some are giant multi-lane white-knuckle nightmares. There are places with good traffic light setups, but traffic lights generally suffer from the same problems of sometimes stopping traffic for no good reason while also encouraging excess speed.
In my current city, I can identify at least 3 intersections that would be better as a roundabout, but I don't have my hopes up.
Yeah, I know what you mean by abusing 4 way stops being abused. Thankfully I moved from there a long time ago.
Also where I moved from recently, they changed a roundabout intersection into a traffic lights intersection. And the traffic used to flow. Now it’s a stand still.
There’s always so many little insights when you use the road daily that a planner will never have unless they do the same.
Melbourne where I am kind of close to now, has an absolute clusterf*ck of overpasses, underpasses, toll ways, free ways, tunnels all coming & going out of a neatly planned grid. They probably think it’s planning perfection while driving it as a non-resident is an absolute nightmare. Sydney which is famously poo poo’d for not being planned in Australia is 10x more straight forward to drive.
They replaced a intersection near me that would get backed up very badly during rush hour with a roundabout that has a much higher capacity and never seems to get backed up.
Roundabouts are the Segway of civil engineering. In theory, a game changing transport innovation. In practice, just a little too mismatched with everyday aesthetics to properly fit in. Dorky and annoying for pedestrians too!
Good old traffic lights have a much better feature of being able to control traffic to allow for pedestrians, give cyclists a head start, give smaller side roads a look in at busy junctions, and giving a platform for traffic monitoring.
They’re being used often in new construction areas. It’s just not likely that they’ll be retrofitted to existing areas due to needing more space than regular intersections.
They are everywhere in the areas around me now. I had a similar sentiment at one time and now they seem pretty common.
I think roundabouts work fantastically well in some places but in others they are unnecessary and in others don't work as well as alternatives. Maybe that's obvious but every so often I feel like they are overapplied — probably because of what you're mentioning, along with the fact they were underapplied in other areas in the past. I've come to like them usually but sometimes it feels like the civil engineers were having too much fun at the cost of practicality.
I think here in China we are not super fan of roundabouts. But we got a 4-lane roundabout with traffic lights [1] and a roundabout on elevated roads with traffic lights. [2]
The key disadvantage of a roundabout is that it takes up more space and is harder to setup than plopping down a couple of stop signs.
They are awesome otherwise, I do like them better for low traffic intersections though because I don't have to stop and think about if the next car is going to yield or not.
I was in Aruba recently, and I discovered that they had entirely replaced their traffic lights with roundabouts. Easier to maintain and more efficient in the island's low-traffic regime.
It's so funny seeing most of the comments, plus the original article, implying that roundabouts are always better or always worse than traffic signals. As someone who used to be a Transportation Engineering professor, they have a time and place where they outperform traffic signals but it's definitely not everywhere. It is known and there are many traffic simulation software tools that will give you a pretty good indication of what will happen if you put a roundabout here or a traffic signal there.
This thread reminds me of when my libertarian friend was explaining to me how traffic shows how everything can work well when everyone acts in their own self interest. Well, sure, except for all the traffic laws, the difference between User and System Optimal that traffic engineers spend much of their lives trying to bridge, and, you know, the fact that it took an enormous effort by government to build smooth roads and put up signs everywhere. Sigh. I'm not saying Transportation Engineering is the most important, innovative field, but funny things happen when not transportation engineers talk about transportation systems.
I think I prefer maybe the simplicity of 4 way (or even 2 way) stops
There are some funny intersection videos from idk what country that have no stop signs or lights or roundabouts and somehow lots of people still manage to get through them
The big difference is that when you have a collision at a 4-way or 2-way stop, it is almost always a "T-Bone" collision, where all the energy hits at a right angle. These collisions kill, especially at speed.
A similar collision on a roundabout is almost always a "glancing" blow, at an angle, and rarely causes injury or death.
Roundabouts force you to slow down when approaching. Stop signs can be ignored. Roundabouts can't.
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.
I agree with this, and I'll offer a rationale. Because the US largely "grew up with cars", the economy has been built around the expectation that folks can drive to work. That means everyone needs to be able to drive. If you can't drive, you likely can't work. That isn't the case in the UK, and you'll notice a lot of these "driver beware" analysis is explained by the fact that driving here is more of a privilege than it is a right in the US. This sort of "mild chaos" is prohibitive for a lot of UK drivers, and they just take the bus.
> 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.
Slowing/calming traffic like this is a good thing. Make it impossible to speed. Enforce the existing 35mph speed limit via concrete rather than allowing cars to rip through a yellow light at 70mph. You're also ignoring this aspect when you call roundabouts "(mostly) worse for cyclists and pedestrians".
> 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).
This point is so under-appreciated. Roundabouts are really good in some cases, but they're over-utilized in England. Imagine if the US had roundabouts on the interstate and you're getting close.
I think the main problem in England is that there is just too much traffic for too little road. I don't think there is a simple infrastructure solution to that problem.
For example I was going to point out that roundabout completely fail when one direction becomes nose to tail congested but when I thought about local examples, I'd rather take that over a set of traffic lights where it becomes near impossible to get out from one direction if the traffic keeps backing up onto the junction.
It would be interesting to know your (friend's) country of origin.
Thank you so much for putting into words what I have feeling but struggling to verbalize. (Boston area, drive for work.)
There is one more downside, they are easy to get lost in, especially in an unfamiliar area. Apple Maps does an OK job guiding me most of the time, but just yesterday I spent an extra 25 minutes going through the same roundabout 3 times before I went the right direction, and each time I had to drive the wrong way, turn around, and then negotiate the same roundabout again.
Roundabouts are perfect when youre confused, just go around and read all the signs 3 times, then select the exit! :)
I live in the US and roundabouts simply don't work.
Not much of America's traffic infrastructure works well. Every month, combined with poorly trained motorists, it contributes to another 9/11's worth of fatalities. The infrastructure you think works, kills enough people for a thirteenth month at the end of every year.
They have their downsides, but "It doesn't work in America" is more informative of American motorists than roundabouts
This led me down somewhat of a rabbit hole looking at roundabouts, then to the official roundabout page from the Department of Transportation, where I couldn't believe my eyes to see that National Roundabout Week is next week: https://highways.dot.gov/safety/intersection-safety/nrw
You almost missed it!
The city I grew up in had no roundabouts back then. Today it does have some, some were even made and removed again since. People there hate roundabouts.
The city I live nearby now has so many roundabouts that I can drive for over an hour without seeing a traffic light. It always had those, people are used to using them.
Guess what works better and barely has any traffic issues at all.
You only need one roundabout to be able to drive for hours without seeing a traffic light. It’s one of the main features of loops.
> Guess what works better and barely has any traffic issues at all.
The one that where mass transit works better.
But yeah, a city still needs cars, and roundabouts are still unbeatable in low-traffic crossings. But they are not the most impacting change a city can make.
As a bicyclist I hate them, at least the smaller ones. Because they slow me down, can't take them with 40 to 50 kph, need to slow down to 30. But that was the intent, yes?
However, crossings with traffic lights I can take at any speed I'm able to, when they are green for me, and I don't need to turn. Or if I can oversee them from afar, and they are empty, and I can give a shit about 'lights'.
Some roundabouts here have bike pass troughs on the side (obviously only works if there is no turn to that side) for speedy drivers like you.
Other than that it's obviously by design. There is no reason to speed at constant 50kph in a city. Nether for a car, motorbike or e-bike.
The think I don’t like about not being able to “speed” at 50kph(!) through a city is that, at least in Australia with it’s excessive compliment of bureaucratic Karens, is the 30 > 50 > 70 > 60 > 40 > 30 > SCHOOL ZONE > 80 > 40 > 50 > 30 nightmare.
Which does two things, raises state revenue and causes drivers to spend way to much time concentrating on how fast they are going rather than driving to suit the conditions and paying focusing to what’s going on in front of them.
And don’t get me started on the pot holes.
Maybe, living in France where maybe half the roundabouts of the world exist, I have been exposed to too much beauty.
But mostly I see roundabouts as one of the most depressing, ugly and environmentally-destructive gimmicks of 20th century car culture.
[edit: for clarity, I am not against roundabouts]
I don't have real expertise in civil engineering
Traffic lights have a smaller physical footprint and require less construction activity.
Traffic lights fit on a cost spectrum from two stop sighs, to four stop signs, to stop signs plus blinking lights, to non-trivial signaling.
First make it work. Then make it good. Then make it fast.
Engineering is not a one size fits all discipline.
[edit: I have a background in urban planning, architecture, and real-estate development]
The footprint is a cost problem once. They don't need power, computers, or technicians to come out and maintain the equipment constantly.
>The footprint is a cost problem once.
Land can approximately be converted to a recurring cost via rents.
You forgot roundabouts with traffic lights.
Here’s one in Australia near Perth:
https://youtu.be/h8lhX9Q6Z5g?si=eloUWLcH8q3eJiZH
And I’m certain I’ve driven through other roundabouts with traffic lights in other states.
In England we even have roundabouts of roundabouts https://en.wikipedia.org/wiki/Magic_Roundabout_(Swindon)
I’ve driven around the Hemel Hempstead one a few times. Very confusing when I first saw the sign.
Ooo! I like that one!
I know of a couple in NSW: one in Albion Park, and another in Bomaderry.
They work well when the peak-hour traffic tends to block some of the entrances. You can use the lights to allow the blocked entrances to flow, then turn the lights off out of peak-hour.
A roundabout can be as simple as a circle painted in the middle of an intersection, plus a bit of signage. It doesn’t have to be a big thing.
> Roundabouts come with this otherwise unused patch of land in the middle. Apparently, it has become common practice around the world to put some random art there, or a little green space, or a fountain, or a "welcome to this town" sign.
Or a dog: <https://en.wikipedia.org/w/index.php?title=Roundabout_dog&ol...>
I wish local councils wouldn't insist on putting in shrubs that block the line of site across the roundabout.
According to Wikipedia, these shrubs are there for a reason. Denmark has found that blocking the line of sight significantly reduces the accident rate by forcing the drivers to slow down and consider only their immediate surroundings. Danish drivers hate them, anyway.
Agreed, it can be really hard to get around a roundabout as a pedestrian if it's not designed for it, and then they make it so both you and people entering don't know each other are there until you're about to get hit.
One additional benefit (or at least an unproven, theoretical benefit): https://www.youtube.com/watch?v=qdbJJ8UhM1I
I like roundabouts over lights at small intersections. I still prefer simple give way/stop that changes the next intersection over roundabouts.
Lights suck unless there’s sufficient traffic.
I've lived some places where 4-way stops were just abused, like Sugarland, TX. England and Ireland are full of roundabouts, some of which are incredibly small, just a painted dot, and some are giant multi-lane white-knuckle nightmares. There are places with good traffic light setups, but traffic lights generally suffer from the same problems of sometimes stopping traffic for no good reason while also encouraging excess speed.
In my current city, I can identify at least 3 intersections that would be better as a roundabout, but I don't have my hopes up.
Yeah, I know what you mean by abusing 4 way stops being abused. Thankfully I moved from there a long time ago.
Also where I moved from recently, they changed a roundabout intersection into a traffic lights intersection. And the traffic used to flow. Now it’s a stand still.
There’s always so many little insights when you use the road daily that a planner will never have unless they do the same.
Melbourne where I am kind of close to now, has an absolute clusterf*ck of overpasses, underpasses, toll ways, free ways, tunnels all coming & going out of a neatly planned grid. They probably think it’s planning perfection while driving it as a non-resident is an absolute nightmare. Sydney which is famously poo poo’d for not being planned in Australia is 10x more straight forward to drive.
They replaced a intersection near me that would get backed up very badly during rush hour with a roundabout that has a much higher capacity and never seems to get backed up.
Roundabouts are the Segway of civil engineering. In theory, a game changing transport innovation. In practice, just a little too mismatched with everyday aesthetics to properly fit in. Dorky and annoying for pedestrians too!
Good old traffic lights have a much better feature of being able to control traffic to allow for pedestrians, give cyclists a head start, give smaller side roads a look in at busy junctions, and giving a platform for traffic monitoring.
I feel like the author would appreciate Milton Keynes, which is an entire city of 180 roundabouts on a grid system:
https://lostcolonials.wordpress.com/2015/09/20/milton-keynes...
Fun for drifting late at night. Like a chav version of tōge from Initial D.
This dreaming about roundabouts is as American as the fantasies about using metric one day.
They’re being used often in new construction areas. It’s just not likely that they’ll be retrofitted to existing areas due to needing more space than regular intersections.
They are everywhere in the areas around me now. I had a similar sentiment at one time and now they seem pretty common.
I think roundabouts work fantastically well in some places but in others they are unnecessary and in others don't work as well as alternatives. Maybe that's obvious but every so often I feel like they are overapplied — probably because of what you're mentioning, along with the fact they were underapplied in other areas in the past. I've come to like them usually but sometimes it feels like the civil engineers were having too much fun at the cost of practicality.
Roundabouts are much more common in the US than they were 10 years ago.
I think here in China we are not super fan of roundabouts. But we got a 4-lane roundabout with traffic lights [1] and a roundabout on elevated roads with traffic lights. [2]
[1] https://maps.app.goo.gl/rY6AH8nUEKvRuk1LA
[2] https://maps.app.goo.gl/Wea6Wt5FwHgKmG4C9
The key disadvantage of a roundabout is that it takes up more space and is harder to setup than plopping down a couple of stop signs.
They are awesome otherwise, I do like them better for low traffic intersections though because I don't have to stop and think about if the next car is going to yield or not.
Roundabouts are superior to other intersection types in nearly every case. Two lane roundabouts are a notable exception.
Two lane roundabouts are fantastic if you’re familiar with the intersection. If you’re not it’s too easy to get shunted out of the roundabout early
I was hoping that it was "404 not found"
I was in Aruba recently, and I discovered that they had entirely replaced their traffic lights with roundabouts. Easier to maintain and more efficient in the island's low-traffic regime.
It's so funny seeing most of the comments, plus the original article, implying that roundabouts are always better or always worse than traffic signals. As someone who used to be a Transportation Engineering professor, they have a time and place where they outperform traffic signals but it's definitely not everywhere. It is known and there are many traffic simulation software tools that will give you a pretty good indication of what will happen if you put a roundabout here or a traffic signal there.
This thread reminds me of when my libertarian friend was explaining to me how traffic shows how everything can work well when everyone acts in their own self interest. Well, sure, except for all the traffic laws, the difference between User and System Optimal that traffic engineers spend much of their lives trying to bridge, and, you know, the fact that it took an enormous effort by government to build smooth roads and put up signs everywhere. Sigh. I'm not saying Transportation Engineering is the most important, innovative field, but funny things happen when not transportation engineers talk about transportation systems.
Reminder that technically a 4-way stop is the smallest possible roundabout.
Not quite. It has to be a 4-way yield and you have to make your left turn after the painted dot/concrete hemiball, not across it.
It is so funny to read this because in reality, roundabouts are some of the worst traffic congestion makers :)
This is completely wrong. Well designed roundabouts work very well.
I think I prefer maybe the simplicity of 4 way (or even 2 way) stops
There are some funny intersection videos from idk what country that have no stop signs or lights or roundabouts and somehow lots of people still manage to get through them
The big difference is that when you have a collision at a 4-way or 2-way stop, it is almost always a "T-Bone" collision, where all the energy hits at a right angle. These collisions kill, especially at speed.
A similar collision on a roundabout is almost always a "glancing" blow, at an angle, and rarely causes injury or death.
Roundabouts force you to slow down when approaching. Stop signs can be ignored. Roundabouts can't.
The advantages aren't "theoretical." It's 100% proven that they're safer, cheaper over the long term, and flow more traffic than a red light.