I remember when we went of a family trip to England in 2000 and my dad (a traffic engineer) brought some of the first roundabouts to the state of Washington.
I helped edit the educational brochures and saw a lot of the intersection data in his office. And it was just as I’d recently learned to drive.
Basically, roundabouts, for most intersections with enough traffic that you’d be comparing it with a four-way stop or a light (or when you’d expect that level of traffic within years, based on development/planning):
-decrease average time spent at an intersection
-cost less to maintain
-are safer for cars
-are safer for pedestrians
-look better
They do take up more space (makes them a challenge in already-developed areas) and they have to be even bigger when you need trucks to get through ‘em. And there’s a learning curve at the beginning (although this is probably lessened now that there are so many more roundabouts in the U.S.).
To the commenter about how they’re harder for pedestrians because it’s more difficult to deal with a car maintaining a constant slow speed than it is from a stop…have you WATCHED people at intersections? People blow through lights all the time, accelerate towards them, slow down like they’re going to stop, then don’t, roll through the crosswalk before stopping, are checking their GPS/phone and not even LOOKING at the road as they go through…roundabouts force drivers to pay attention, too.
A car going a consistent speed is VERY easy to avoid - cars that may or may not stop, coming from multiple directions? Those lines on the street do nothing to stop the car from killing you.
A couple other nice aspects to roundabouts is that generally collisions between vehicles will happen with the front of one car colliding to one of the back corners of another car, which is much less dangerous than a t-bone accident. There are also clever variations of the 4-way intersection design which force drivers to take wider right turns, which makes it so that a bicyclist doesn't hide in the car's blind spot. They would be visible through the front windshield when the driver crosses the bike lane.
These are examples of good design philosophies to build into intersections. The typical driver is at worst not very attentive, so you should design things so that it is as hard as possible for a driver to make a mistake.
I do agree with one of the other comments about how roundabouts can be awkward (for both other cars and pedestrians) when it's unclear which exit a driver in the roundabout intends to use. It's also possible for roundabouts to freeze up when pedestrians block one of the exits, which can stop traffic trying to go to any of the other exits. This feels suboptimal so I hope someday we find a solution that can solve all the issues at once.
With respect to signalling, I think it's undeniably harder with roundabouts than with a 4-way intersection. The ideal approach with a roundabout is that you're going around a left bend and you have to signal right just before the exit you intend to take. This doesn't offer a lot of time for other drivers and for pedestrians to see your signal before you take that exit.
Consider 4-way intersections. In those, you usually come to a complete stop at a stop sign or traffic light. At that time (or much earlier) you can signal left or right. Additionally, many intersections are designed so that the lane of your car indicates what direction(s) you'll probably go, so if you forget to signal, other drivers can still anticipate your movements.
I think stepping back, good attentative drivers with good training are usually not the ones to worry about. Even if everyone had good training, 2% of the drivers on the road are going to be performing at about the 2% level on their personal driving quality bell curve. They're perhaps sleep deprived or feeling lazy or they're having a bad day, or maybe it's those things plus they're driving in a part of town they're not familiar with. You want the road designs to make it relatively hard for those people (and anyone with open eyes) to get into an accident, and if they do get into an accident, it should be one at low speeds with minimal injuries.
Roundabouts are certainly good at the "if you do get into an accident" case, but I think the attentativeness required has some tradeoffs when it comes to predicting other drivers. 4-way intersections are pretty bad overall, but they sure give a lot of opportunity to figure out what direction other people are planning to go
Drove tractor-trailer for many years. There were times at busy roundabouts that I would have to come to a complete stop before getting a break in traffic to enter the roundabout. That would create quite a backup. Other times I would be negotiating the roundabout and have cars try to pass me and cut me off. I often times had to hog all the lanes so that I wouldn't hit cars trying to come around me. Roundabouts are the bane of trucks.
NJ removed many of them in the 1990's. Once traffic reaches a certain level, they can become impossible to enter and many people just don't understand the road rules when in them. I used to live near Flemington NJ and the circle could create consternation for even the most experienced drivers. They are installing them at a rapid rate here in PA on US 222 which is heavily traveled by tractor trailers, but remains a two lane road in many areas. In my mind it's a temporary measure until traffic increases and traffic lights will be required. On that road it can still be quite difficult to make a left turn in the spots not proximate to the roundabouts. I am not a fan.
Part of the solution to that can be found in Britain - small, almost nominal, roundabouts, almost flat, so big vehicles can over-run them if necessary. I'm told that they are efficient at keeping most vehicles apart...
I’ve lived in the Netherlands for almost three years (previously Louisiana) and there are obstructions, roundabouts, and speed bumps everywhere. I used to think they were insane. Why would they intentionally obstruct the free flow of cars? Then I realized it’s only insane if you think a road’s primary purpose is to get cars from one place to another as fast as possible. And once that isn’t the only objective it makes a lot more sense. Car crashes are almost non-existent where I live.
Roundabout don't seem like they obstruct the free flow of cars, at least compared to a 4 way stop that backs up for a couple hundred yards in heavy traffic, or a light that may force you to stop and wait in the middle of the night with no traffic.
I think the post was intended to be taken with a little more nuance, they do not obstruct the flow, but the speed of vehicles. In truth, the flow is usually more consistent, with fewer queues.
As a former resident of Carmel Indiana (roundabout capital of the country) thank you for seeing the light on our holiest of road infrastructure. Next please convince your little planner/engineer friends to put in a bike path on all arterial roads like we did. It makes the suburbs much much more approachable for teenagers without a car
Roundabouts have e been springing up in our city over the past few years at congested intersections that formerly had traffic lights. There was a little resistance at first as drivers were unsure about how to navigate them, despite very clear signage both above the road and on the road surface. As people have become used to them it has become obvious how much better the roundabouts work for smooth traffic flow than what we had previously. Speaking personally, I would say that the introduction of roundabouts has been a positive improvement in the transportation system of our community.
In Waterloo, Ontario, Canada there's a roundabout at the intersection of 2 - 4 lane arterials. After many collisions, vehicle to vehicle and to pedestrians, it's being modified now with raised, "speed bump" pedestrian walkways and pedestrian initiated crossing signals. There's nothing wrong, except drivers who can't seem to remember to look out for others.
Can you provide a diagram of a multi lane roundabout? I'm particularly interested in how pedestrian crossings fit into them.
Single lane roundabouts feel easier to navigate than multi lane ones, especially when you find yourself needing to change lanes within the roundabout itself.
Is the need to pay closer attention to maneuvering within a roundabout a reason for fewer accidents?
I confess, I think my stress level goes up when I encounter a roundabout.
The key thing to remember about multi-lane roundabouts is to get into the correct lane BEFORE entering the roundabout. Most vehicle accidents at roundabouts occur because people are in the wrong lane and try to cut across lanes to reach the exit they are aiming for. In a two-lane roundabout serving four roads the lefthand lane is for either going straight ahead (I.e. exit 2) or turning left (exit 3.) The righthand lane can also go straight ahead (exit 2) or turn right (exit 1.) The problems occur when vehicles in the righthand lane try to turn left (take exit 3.) Typically, lane markings will guide you in the correct direction as long as you are in the correct lane when entering.
This happens regularly on US 202 in Flemington NJ. You have to have eyes in the back of your head to make sure someone in the wrong lane doesn't hit you.
Every time I tell people about roundabouts here in Orange County, they say something like “they are too hard to navigate!” I do get how maybe a very inexperienced driver may have challenges, but anyone with some background driving who still can’t successfully navigate through one should simply not be driving at all.
In Australia, most roundabouts are terrible for pedestrians and cyclists through a combination of design and road rules.
Australian road rules require turning traffic at an intersection give way to pedestrians crossing the road the drivers are entering, but not if that intersection is a roundabout. On small streets, this is confusing, and rarely you'd see a zebra crossing added to prioritise people walking. Where there's one, it's normally just one, leaving three other legs without pedestrian priority over traffic. It is incomprehensible.
On multi-lane arterials, zebra crossings are not an appropriate treatment road safety wise (due to pedestrian-to-farther-lane line of sight potentially blocked by a vehicle in a nearer lane), so mostly pedestrians get nothing other than a stripe of asphalt indicating a place where they are supposed to cross... four or six lanes of rapidly moving traffic. In most places, it's just a game of not getting killed by traffic while trying to cross. (Sometimes a traffic light crossing is added, but that is generally rare.)
What really breaks my brain apart, however, is that cyclists in roundabouts, whilst moving along the circle, do get priority over incoming traffic but must yield to the exiting traffic. That's irrational, counterintuitive, and just incredibly bad all around.
The Dutch design roundabouts well—and well here also meaning differently—and it's hard to understand why Australian road engineering is struggling to replicate.
Roundabouts are everywhere now (I’m in Maryland) and engineers and planners (both) have it wrong when it comes to residential areas, main streets, and retail environments.
“Slower traffic” is not inherently safer for pedestrians if it is still moving. From a pedestrian’s perspective, a vehicle at 15–20 mph that never fully stops is less predictable—and often more intimidating—than a stopped car with a clear right-of-way signal. Predictability, clarity, and pedestrian priority matter more than speed.
In neighborhood and retail settings, roundabouts fundamentally invert the hierarchy. Pedestrians are expected to negotiate with vehicles rather than rule the intersection. That undermines walkability, discourages casual crossings, and degrades retail performance. Successful retail streets depend on frequent, intuitive crossings and moments where cars are forced to pause—creating eye contact, decision points, and opportunities to turn in, park, or linger.
I'd encourage you to look at some of the many case studies. On the safety front, speed management is vital. When people slow down their cars, they yield to people at crosswalks and are much less likely to be involved in a crash.
Some Colorado winter tourist towns had dramatic corridor retail improvement after converting to roundabouts. Their success was more focused on business success than pedestrians, though, because of weather.
You can buy degrees, eh? - Don't know, I had to study hard, work hard and my little family had to cut back...
I remember when we went of a family trip to England in 2000 and my dad (a traffic engineer) brought some of the first roundabouts to the state of Washington.
I helped edit the educational brochures and saw a lot of the intersection data in his office. And it was just as I’d recently learned to drive.
Basically, roundabouts, for most intersections with enough traffic that you’d be comparing it with a four-way stop or a light (or when you’d expect that level of traffic within years, based on development/planning):
-decrease average time spent at an intersection
-cost less to maintain
-are safer for cars
-are safer for pedestrians
-look better
They do take up more space (makes them a challenge in already-developed areas) and they have to be even bigger when you need trucks to get through ‘em. And there’s a learning curve at the beginning (although this is probably lessened now that there are so many more roundabouts in the U.S.).
To the commenter about how they’re harder for pedestrians because it’s more difficult to deal with a car maintaining a constant slow speed than it is from a stop…have you WATCHED people at intersections? People blow through lights all the time, accelerate towards them, slow down like they’re going to stop, then don’t, roll through the crosswalk before stopping, are checking their GPS/phone and not even LOOKING at the road as they go through…roundabouts force drivers to pay attention, too.
A car going a consistent speed is VERY easy to avoid - cars that may or may not stop, coming from multiple directions? Those lines on the street do nothing to stop the car from killing you.
A couple other nice aspects to roundabouts is that generally collisions between vehicles will happen with the front of one car colliding to one of the back corners of another car, which is much less dangerous than a t-bone accident. There are also clever variations of the 4-way intersection design which force drivers to take wider right turns, which makes it so that a bicyclist doesn't hide in the car's blind spot. They would be visible through the front windshield when the driver crosses the bike lane.
These are examples of good design philosophies to build into intersections. The typical driver is at worst not very attentive, so you should design things so that it is as hard as possible for a driver to make a mistake.
I do agree with one of the other comments about how roundabouts can be awkward (for both other cars and pedestrians) when it's unclear which exit a driver in the roundabout intends to use. It's also possible for roundabouts to freeze up when pedestrians block one of the exits, which can stop traffic trying to go to any of the other exits. This feels suboptimal so I hope someday we find a solution that can solve all the issues at once.
The keys to drivers not being clear about their intentions are (1) PROFESSIONAL (not relying on a relative) driver training and clear signaling.
With respect to signalling, I think it's undeniably harder with roundabouts than with a 4-way intersection. The ideal approach with a roundabout is that you're going around a left bend and you have to signal right just before the exit you intend to take. This doesn't offer a lot of time for other drivers and for pedestrians to see your signal before you take that exit.
Consider 4-way intersections. In those, you usually come to a complete stop at a stop sign or traffic light. At that time (or much earlier) you can signal left or right. Additionally, many intersections are designed so that the lane of your car indicates what direction(s) you'll probably go, so if you forget to signal, other drivers can still anticipate your movements.
I think stepping back, good attentative drivers with good training are usually not the ones to worry about. Even if everyone had good training, 2% of the drivers on the road are going to be performing at about the 2% level on their personal driving quality bell curve. They're perhaps sleep deprived or feeling lazy or they're having a bad day, or maybe it's those things plus they're driving in a part of town they're not familiar with. You want the road designs to make it relatively hard for those people (and anyone with open eyes) to get into an accident, and if they do get into an accident, it should be one at low speeds with minimal injuries.
Roundabouts are certainly good at the "if you do get into an accident" case, but I think the attentativeness required has some tradeoffs when it comes to predicting other drivers. 4-way intersections are pretty bad overall, but they sure give a lot of opportunity to figure out what direction other people are planning to go
Drove tractor-trailer for many years. There were times at busy roundabouts that I would have to come to a complete stop before getting a break in traffic to enter the roundabout. That would create quite a backup. Other times I would be negotiating the roundabout and have cars try to pass me and cut me off. I often times had to hog all the lanes so that I wouldn't hit cars trying to come around me. Roundabouts are the bane of trucks.
NJ removed many of them in the 1990's. Once traffic reaches a certain level, they can become impossible to enter and many people just don't understand the road rules when in them. I used to live near Flemington NJ and the circle could create consternation for even the most experienced drivers. They are installing them at a rapid rate here in PA on US 222 which is heavily traveled by tractor trailers, but remains a two lane road in many areas. In my mind it's a temporary measure until traffic increases and traffic lights will be required. On that road it can still be quite difficult to make a left turn in the spots not proximate to the roundabouts. I am not a fan.
Part of the solution to that can be found in Britain - small, almost nominal, roundabouts, almost flat, so big vehicles can over-run them if necessary. I'm told that they are efficient at keeping most vehicles apart...
Funny how the rest of the world has known this for decades.
I guess it's about societal values. When engineers prioritize getting cars to their destination above everything else, that reflects a value.
Prioritizing democratizing all forms of personal transport, including walking biking and micromobility, requires a different engineering approach.
And the root, land use regulations!
I’ve lived in the Netherlands for almost three years (previously Louisiana) and there are obstructions, roundabouts, and speed bumps everywhere. I used to think they were insane. Why would they intentionally obstruct the free flow of cars? Then I realized it’s only insane if you think a road’s primary purpose is to get cars from one place to another as fast as possible. And once that isn’t the only objective it makes a lot more sense. Car crashes are almost non-existent where I live.
Roundabout don't seem like they obstruct the free flow of cars, at least compared to a 4 way stop that backs up for a couple hundred yards in heavy traffic, or a light that may force you to stop and wait in the middle of the night with no traffic.
I think the post was intended to be taken with a little more nuance, they do not obstruct the flow, but the speed of vehicles. In truth, the flow is usually more consistent, with fewer queues.
As a former resident of Carmel Indiana (roundabout capital of the country) thank you for seeing the light on our holiest of road infrastructure. Next please convince your little planner/engineer friends to put in a bike path on all arterial roads like we did. It makes the suburbs much much more approachable for teenagers without a car
Roundabouts have e been springing up in our city over the past few years at congested intersections that formerly had traffic lights. There was a little resistance at first as drivers were unsure about how to navigate them, despite very clear signage both above the road and on the road surface. As people have become used to them it has become obvious how much better the roundabouts work for smooth traffic flow than what we had previously. Speaking personally, I would say that the introduction of roundabouts has been a positive improvement in the transportation system of our community.
In Waterloo, Ontario, Canada there's a roundabout at the intersection of 2 - 4 lane arterials. After many collisions, vehicle to vehicle and to pedestrians, it's being modified now with raised, "speed bump" pedestrian walkways and pedestrian initiated crossing signals. There's nothing wrong, except drivers who can't seem to remember to look out for others.
Can you provide a diagram of a multi lane roundabout? I'm particularly interested in how pedestrian crossings fit into them.
Single lane roundabouts feel easier to navigate than multi lane ones, especially when you find yourself needing to change lanes within the roundabout itself.
Is the need to pay closer attention to maneuvering within a roundabout a reason for fewer accidents?
I confess, I think my stress level goes up when I encounter a roundabout.
The key thing to remember about multi-lane roundabouts is to get into the correct lane BEFORE entering the roundabout. Most vehicle accidents at roundabouts occur because people are in the wrong lane and try to cut across lanes to reach the exit they are aiming for. In a two-lane roundabout serving four roads the lefthand lane is for either going straight ahead (I.e. exit 2) or turning left (exit 3.) The righthand lane can also go straight ahead (exit 2) or turn right (exit 1.) The problems occur when vehicles in the righthand lane try to turn left (take exit 3.) Typically, lane markings will guide you in the correct direction as long as you are in the correct lane when entering.
This happens regularly on US 202 in Flemington NJ. You have to have eyes in the back of your head to make sure someone in the wrong lane doesn't hit you.
Every time I tell people about roundabouts here in Orange County, they say something like “they are too hard to navigate!” I do get how maybe a very inexperienced driver may have challenges, but anyone with some background driving who still can’t successfully navigate through one should simply not be driving at all.
The design nuances matter.
In Australia, most roundabouts are terrible for pedestrians and cyclists through a combination of design and road rules.
Australian road rules require turning traffic at an intersection give way to pedestrians crossing the road the drivers are entering, but not if that intersection is a roundabout. On small streets, this is confusing, and rarely you'd see a zebra crossing added to prioritise people walking. Where there's one, it's normally just one, leaving three other legs without pedestrian priority over traffic. It is incomprehensible.
On multi-lane arterials, zebra crossings are not an appropriate treatment road safety wise (due to pedestrian-to-farther-lane line of sight potentially blocked by a vehicle in a nearer lane), so mostly pedestrians get nothing other than a stripe of asphalt indicating a place where they are supposed to cross... four or six lanes of rapidly moving traffic. In most places, it's just a game of not getting killed by traffic while trying to cross. (Sometimes a traffic light crossing is added, but that is generally rare.)
What really breaks my brain apart, however, is that cyclists in roundabouts, whilst moving along the circle, do get priority over incoming traffic but must yield to the exiting traffic. That's irrational, counterintuitive, and just incredibly bad all around.
The Dutch design roundabouts well—and well here also meaning differently—and it's hard to understand why Australian road engineering is struggling to replicate.
Roundabouts are everywhere now (I’m in Maryland) and engineers and planners (both) have it wrong when it comes to residential areas, main streets, and retail environments.
“Slower traffic” is not inherently safer for pedestrians if it is still moving. From a pedestrian’s perspective, a vehicle at 15–20 mph that never fully stops is less predictable—and often more intimidating—than a stopped car with a clear right-of-way signal. Predictability, clarity, and pedestrian priority matter more than speed.
In neighborhood and retail settings, roundabouts fundamentally invert the hierarchy. Pedestrians are expected to negotiate with vehicles rather than rule the intersection. That undermines walkability, discourages casual crossings, and degrades retail performance. Successful retail streets depend on frequent, intuitive crossings and moments where cars are forced to pause—creating eye contact, decision points, and opportunities to turn in, park, or linger.
I'd encourage you to look at some of the many case studies. On the safety front, speed management is vital. When people slow down their cars, they yield to people at crosswalks and are much less likely to be involved in a crash.
Some Colorado winter tourist towns had dramatic corridor retail improvement after converting to roundabouts. Their success was more focused on business success than pedestrians, though, because of weather.