There are also "traffic calming circles", which are not roundabouts. "Traffic calming circles should not be confused with roundabouts, which are designed to handle much higher traffic volumes and reduce vehicle delay." - https://www.sfbetterstreets.org/find-project-types/pedestria...
Indeed, wasn't until 2011 or so until I saw my first roundabout in the USA.
For my other Americans, read the Australian's post above. Can get across an entire town without stopping as a reason to remake our towns with roundabouts.
"Fewer than what's in France and the UK" is an interesting metric. Apparently it doesn't matter that there are so many that the only way to get through certain parts of various cities in most states is to drive through multiple roundabouts in serial. That certainly qualifies as "few and far between" simply because there are fewer than what's in France
It depends where you are. Some cities are more on board with them than others. You do see them quite a bit now at the end of new or reconstructed freeway exit ramps, as opposed to the previously more usual stop signs or traffic signals.
the resistance is a problem. there are a few in Pasadena, CA on Los Robles between California and Raymond where it's a roundabout, with stop signs on each entrance. the worst of both worlds.
We have plenty of them. They're usually pretty miserable because your average American driver is a fucking moron and they're best not deployed unless there's a safety reason to do so.
I grew up in a town in Australia nicknamed "The City of Roundabouts". Essentially all intersections in the entire town are roundabouts, including two lane ones, etc. It's quite common to drive the entire length of town (~20 blocks) in reasonably heavy traffic without ever stopping. On a good day you do it in 2nd gear, the whole way. At night you can do it in 3rd gear, because it's exceptionally easy to see headlights of any car you need to yield to.
Four way stops do not exist (I've never seen one in all of Australia), and they are still the strangest concept for me living in Canada. They feel like a colossal waste of time and energy, and vastly worse than roundabouts.
Safety aside, roundabouts lower traffic significantly by never forcing cars to stop.
Congestion increases as cars need to stop because of the inevitable latency propagating along the tails, and having more than one traditional intersections along the way can only make things even worse, so any solution to prevent cars from slowing down to a stop would mitigate those effects.
Until you do what Cambridge, MA has done twice near my house: put a traffic light just outside the roundabout, so when the light turns red, traffic inevitably backs up through the roundabout, locking it up entirely.
They do that in Sweden all the time. I have no idea how a country that has some amazing minds can come up with the worst road infrastructure designs possible. Most of it’s unsafe so they just lower the speed limit.
Having lived in Boston and other areas with roundabouts, I can with confidence assert that this is a Boston traffic design problem, not a roundabout one.
note that proper spinlock procedure is to not leave the roundabout unless there is room to do so completely
this avoids complete deadlock until the entire roundabout is full of drivers who refuse to take any unblocked exit, while continually offering each the ability to do so
> not leave the roundabout unless there is room to do so completely
I don't understand how that helps. The problem is there are too many cars in the rotary, so no amount of not leaving the rotary will unblock it. It seems like you should not enter unless there's room to exit, but on some of these, you can't both see the exiting traffic light and safely merge into moving rotary traffic, so I don't really blame drivers who enter the rotary and find the light turns amber then red on them.
as an ai language model, i cannot speak to your particular intersection, but the idea is that if say just one car is waiting for the blocked exit, circling would allow other exits to continue to function, by following the general rule of 'do not stop once entering the roundabout'
i could also imagine that anyone waiting behind someone who is deadlocking might have success sending a signal to the blocking process, unless they have committed to a non-reentrant exit routine
There is an issue with them though. If there is very unbalance traffic flow in one direction through the roundabout, traffic from the perpendicular direction tends to be perpetually forced to yield. And only being allowed in the roundabout by some graceful soul.
This can happen on routes where there are multiple chained roundabouts, that usually results in traffic coming at an even rate with no gaps in between.
Roundabouts often lead to cars being forced to stop. The stop is however generally much shorter, occasionally not needed, and when cars leaves at the first turn then the other cars from other directions can simultaneously use the roundabout at the same time. Many roundabouts here where I live also have extra roads for some direct right turns where such traffic flow is common, which mean that those cars don't even need to enter the roundabout and just need to be observant of cars existing towards the same direction.
They’re often worse in heavy traffic situations. Especially if you have two entrances that feed heavy traffic into the roundabout at peak times, the one that has to yield can end up basically locked out of the flow.
Yes traffic lights can be far better in heavy traffic - at least everyone gets a turn. In some roundabouts I've driven through, where there is a "main" way the cars coming from the other directions often get locked out as people queue through it. It works out if people have some courtesy and take turns but that's not always a good basis for traffic planning.
If the heavy traffic or the locked out traffic does a right turn in the roundabout, then a solution to this is a bypass lane. This works very well for letting traffic through and opening up the roundabout.
Multi-lane roundabouts help when theres a clog downstream of the roundabout.
Roundabouts are also great if you have more than 4 roads meeting.
But yeah, in general roundabouts shine the most in low-traffic intersections that previously had lights. They make driving in those are so much nicer, drivers basically never have to stop.
My experience is that roundabouts help but don't solve. E.g. if there is a complete traffic jam, you may actually increase the risk of collision due to negotiations about right of way happening every time a car can move forward.
Some cities in Europe have so many roundabouts, and two or three lane roundabouts with complex exit decisions you need to make on a split second - it's actually very confusing to navigate.
You're never going to "solve" traffic problems when people are driving cars, but when you look at the data, crashes that lead to injuries and, importantly, fatalities, go down with roundabouts.
and two or three lane roundabouts with complex exit decisions you need to make on a split second - it's actually very confusing to navigate.
I think you're confusing what today might be called a "rotary" (?) with a modern roundabout. Whatever you call it, I don't think anyone builds what you're describing anymore.
"My experience is that roundabouts help but don't solve"
Because they don't remove the idiots from the roads. The same people who willfully ignore right of way at stops signs also ignore right of way in the roundabout.
> My experience is that roundabouts help but don't solve. E.g. if there is a complete traffic jam
Agree, when at or near 100% utilisation, its slower than a normal junction.
> you may actually increase the risk of collision due to negotiations about right of way happening every time a car can move forward.
That shouldn't be the case. Ideally you should always have priority from one direction (like in the UK, germany and the netherlands.) The generally rule is that when you come to the round about, if you see someone on your right(in the UK, left everywhere else I imagine) you stop and wait for them to drive past.
> two or three lane roundabouts with complex exit decisions you need to make on a split second
The driving exam will test you for this in the EU. The lane you chose is directly related to where you need to exit. If you are going straight over, or less, then its the outer most lane. Anything more than 180 degrees you take the inner lane. Exceptions will be clearly marked in both floor markings and signs well before entry.
This is near where I live and it is indeed safe, mainly because everyone drives incredibly slowly and cautiously since the experience is scary as hell.
Using roundabouts of roundabouts it's actually possible to build a 3 dimensional roundabout where traffic along the x, y and z axis can safely meet on the surface of a sphere.
Well, when you mention it, I do think it's possible to join these 3d roundabouts into a 4d roundabout, essentially putting them on the vertices of a tesseract, permitting drivers in 4 dimensional space to safely meet on the 3d-dimensional surface of a 4-dimensional hyper-sphere.
Of course it's a real spaghetti intersection where you need to potentially navigate dozens of 2D roundabouts to get to any given direction. Which coincidentally also is true for the 2D road network where I live.
You only need to know one fact to navigate it: the middle is not a roundabout, ignore the fact that it is round.
Every driver in the UK is used to sequences of two or three roundabouts, they are part of the driving test. As long as you are not bamboozled by the pseudo roundabout in the middle, you just navigate it based on principles you already know.
As a right hand driver since 40 years I can't wrap my head around the combo roundabouts. I get terrified just looking at youtube drivers trying to explain how they work in England.
From experience, there's a lot of people in the UK that don't truly know what to do at a double mini roundabout.
As other comments have noted, when drivers are less clear on the rules they tend to drive more slowly and cautiously - I think that makes double roundabouts "work out" most of the time.
You do need to practice them. When I was learning my instructor devoted significant time to them. If you come from a country that doesn't have them, it's not irrational to worry that you aren't going to pick up how to manage them instantly. You need to make several decisions in succession, at the same time as doing several lane merges. But they're not rocket science. If you make a simple mistake, you just end up going the wrong way and have to turn round somewhere.
Holders of foreign driving licences should probably be required to do a course, including these at least, before being allowed to use their licence here.
> because everyone drives incredibly slowly and cautiously since the experience is scary as hell
Apparently there are fewer accidents on the roads when the traffic lights aren’t working. The reason is exactly that - everyone is terrified and drives really slowly to make up for it.
Just to throw off the statistics: We have a road in town that used to be a straight run through the forest. Suddently it got a yield sign and a bus road crossing it. This ofcourse lead to a number of accidents with cars driving into busses not noticing the yield sign. So next step was stop signs. Still lots of accidents though, since this road has been alone so long and was built for 70 km/h from the start so you don't get any hints about that you should slow down. Then came the thick white lines across the road at regular intervals before the crossing. Still accidents. Now they built some stone divider between the lanes so you have to go a little to the side and can't blow straight through the crossing. I'm just waiting for the speed bumps, that is usually the first stage already, bit confusing that they didn't do that yet.
I’ve always thought that the safety effect of the roundabouts - is not anything related to it’s traffic flow properties, but rather the fact that roundabouts are confusing and people slow down and proceed with caution.
We could accomplish the same with other forms of creative driver-hostile road construction and deliberately unproductive signage.
I’m from rural Ireland, and I always remember my first roundabout - I used go driving with my dad when learning, and as the weeks progressed I’d get closer and closer to Killarney which was the nearest town. Coming from our side the first thing you meet is a roundabout with 3 exits, one bringing you out the roads that bypass the town, one to the town centre, and one to a housing estate off the roundabout. As I joined the roundabout I met a woman driving against me on the roundabout taking a shortcut to her exit of the housing estate - frightened the shit outta 16 year old me, my dad was spooked too. I managed to make room enough for her to pass - she was oblivious. My dad actually knew her, lived there all her life, she must have driven that road 1000 times - how often was she taking that shortcut
I'm not a traffic engineer, but I think roundabouts take more space than an equivalent signal or stop sign intersection. The article says that many places are starting to default to roundabouts, but many intersections are likely going to be difficult to upgrade.
Interesting that there are no listed downsides. I saw a more balanced article a while back and recall that it listed cost (especially of the additional real estate, since roundabouts are larger) as being one downside. And in built-up cities, it's basically impossible to convert traditional intersections to roundabouts, because there's simply no room.
It is nice to not have to pay for replacement signals, or have to deal with power outages that kill the signals though.
Roundabouts are great (and common where I live), but a downside is they can be difficult for pedestrians to cross. You need crossings that are set back from the exits, but this also makes it a longer path for the pedestrian.
This is certainly an issue. There is a roundabout on my morning commute that regularly has pedestrians crossing inside the roundabout (alongside cars on the outside) because that's the most direct route.
Drivers anticipating their merge into roundabout are often too distracted to notice pedestrians intending to cross, and any pedestrian crossing the outflow of a roundabout can trigger a traffic backup that interferes with the flow of the circle itself and surprise drivers who expect it to stay moving.
They have their benefits in some intersections, but they also have tradeoffs that make them very poor for others.
I disagree. As a pedestrian, I only have to worry about cars coming from 2 directions (on to/off the roundabout) instead of 4 at an intersection.
I'm confused by your comment that drivers merging into a roundabout are too distracted.
As a driver merging into a roundabout I find I have far less cognitive load. I only have to look for pedestrians crossing in front of me and cars coming from the left. When coming off the roundabout I only have to check for pedestrians crossing the exit I want to take.
At an intersection, all these checks are mashed together into. I have to keep track of all the cars at the intersection plus the pedestrians that may be crossing in front of me and the exit I want to take.
It depends on the roundabout. A low traffic, single-lane roundabout is pretty straightforward. There are also heavy traffic two-lane roundabouts in my area. One is pretty much impossible for a pedestrian to traverse. (Not that it's in a pedestrianized area anyway.) The other two can only be traversed at relatively nearby traffic lights.
I see near-accidents all the time, when a driver is stopped at the entrance to a roundabout, looking left at the cars, and then a pedestrian (or more likely, a cyclist/escooter rider) comes from the right. The driver starts going when there's a clearing in the cars, before realizing that there's someone approaching from the right (I'm in the US, so cars are approaching from the left).
With the exception of decorative 1-lane roundabouts in sleepy residential neighborhoods, all the roundabouts I encounter in Central and Southern California are 2-3 lane circles with various lane->exit mappings, some of which overlap and some of which are exclusive.
Drivers coming into them, who want to actually benefit from the roundabout and not just turn it into an awkward stop sign, are responsible for reversing the exit to lane mapping, then timing their approach to the intersection with an opening that will let them reach to their lane while maintaining a flow. If they can't manage to do that, of course they're supposed to stop and yield until an appropriate opening becomes available.
Inevitably, the designated pedestrian crosswalk is some 5-10+ feet prior to where the car would have to stop if it does need to yield while awaiting an opening.
Compared to a signaled intersection or a 2/4-way stop, where the pedestrian crossing coincides with a natural traffic stop, this basically means that approximately zero cars actually stop for pedestrians. Some are too busy to notice and others just don't want to have to deal with a stop and so ignore their responsibility.
I assume you must live somewhere else, where roundabouts are smaller and play some different role than here.
I'd argue that 1 lane roundabouts are far from decorative in residential neighbourhoods and are safer and allow for a better flow of traffic.
I'm slightly confused by your description, but it sounds like traffic lights for the pedestrian crossings would be a better option (which is often the case with the bigger roundabouts in the UK). Are the roundabouts you referring to like this one https://maps.app.goo.gl/xfxzDWTx4a7WPasUA or smaller?
At least if we are talking about the US, it is a fact that many drivers struggle and tunnel vision. Probably because they are so uncommon. It's great that you don't. Drivers that turn into drooling idiots may be the exception rather than the rule, but it happens frequently enough at the traffic circle in my neighborhood that I've learned to treat it with more caution than any other crossing in the entire city.
> As a driver merging into a roundabout I find I have far less cognitive load. I only have to look for pedestrians crossing in front of me and cars coming from the left. When coming off the roundabout I only have to check for pedestrians crossing the exit I want to take.
I find I sometimes miss pedestrians waiting to cross from the right, because I must look left to merge with oncoming traffic and it's hard to look hard left and to the right at the same time.
At a signalized intersection, if all parties follow the signals, there's often no situation where I'm supposed to be looking in both directions for conflicts.
If I travel straight through the intersection on a green light, there should be no conflict with pedestrians (although one must always be alert). There may be a stopped or slow vehicle in front if the exit is congested. If an unprotected left turn is allowed, I must be aware of that potential conflict while I traverse the first half of the intersection, and if right on red is allowed, I must be aware of that potential conflict as I traverse the second half of the intersection. It's of course useful to be aware of potential for other parties to violate their signals, but look mostly straight but to the left for the first half and mostly straight but to right for the second half works for turns and red light violators ... and mostly straight is pretty good for pedestrians crossing against the light.
For turns, pedestrians are in the same direction you're heading, and often the same direction you're looking. Right on red is an exception, but one typically stops behind the line and looks around for pedestrians before crossing the line and looking for an opportunity to merge in.
For safety, pedestrian crossings should be moved away from roundabouts, where drivers will see them better, but then that increases the path length for pedestrians and acceptance is low.
> As a driver merging into a roundabout I find I have far less cognitive load.
What I've seen first hand in Ontario/Canada is that there's a huge increase in cognitive load simply because the roundabouts are still fairly new. Most drivers were never taught about them. They've just appeared. And they aren't completely intuitive for many drivers -- so their entry/exit isn't always ideal/safe.
>Drivers anticipating their merge into roundabout are often too distracted to notice pedestrians intending to cross
This is so true that it happens constantly at a roundabout in my neighborhood that has stop signs and white stripes at the pedestrian crossing, right before the merge. Even people in the right turn only lane do it.
Yeah but who cares about pedestrians, or bikes, or anything other than 2-ton metal boxes carrying 1 person at a time. Give me 3 lane roundabouts onto 6-lane stroads please baby!
There are roundabouts in England that are just a painted white circle in the middle of the intersection. Those work once the population knows how to handle roundabouts though. In the US, people barely comprehend regular roundabouts and in my town the larger one actually has traffic lights controlling the roundabout. So all the cost of the roundabout + all the cost of lights but none of the traffic flow benefits.
The greatest thing about roundabouts is that they protect against the idiot that goes through an intersection at full speed. He does that either because he is passed out behind the wheel or because he did not notice a stop sign and thought he had the right of way, or maybe because he just does not care.
Well with a roundabout if you just go straight ahead you hit the center circle. Good roundabouts always have a slight hill and some kind of barrier (a tree or some kind of statue) in the center so that the guy that just goes straight through will hit something in the center and wont come out the other side and will thus be less likely to kill an innocent person.
Single lane roundabouts are usually a good idea if the cost justifies it. Double and more lane roundabouts probably should be avoided in the US; they include rather obscure rules as to which lane you are allowed to drive in at any moment and americans do not like to learn new rules.
As long as that center circle is high enough. I had a woman in a Toyota (Camry?) fly over one at about 45+mph and slam into me as I looped around it. Totaled her car, broke parts off my Explorer (repairable). Her son then tried to attack me with my bumper.
She kept insisting I turned in front of her (technically true, I was in a roundabout). She was arrested for drunk driving, and, later on, fined for all the flowers she damaged in the circle and the median she also ran over on her way into the intersection.
The curb she flew over and some brick paving stones used as the perimeter of the little garden, which was enough to stop non-drunk drivers, but no wall or anything.
I came up to a roundabout near Henley in the UK and saw a little lady in a big BMW driving around it the wrong way. It was particularly terrifying as I was on a motorbike. I dread to think what would have happened if I had got there a few seconds earlier.
Good roundabouts always have a slight hill and some kind of barrier (a tree or some kind of statue) in the center
Interestingly enough, a new roundabout was installed in my neighborhood. We considered something pretty to look at in the middle, but the city said no way. "Emergency vehicles need to be able to go through the middle at full speed". Meanwhile, busses have zero issues negotiating the circle at normal driving speeds...
That's more like a trafic circle or whatever to call it. Used where there isn't enough space for a full roundabout. We had them close to school but they took them away again 20 years later. Since this was close to the fire station, emergency vehicles need to be able to go over them. Also busses because no space for them to drive around.
This kind of roundabout is used to join one large road to one or more small road (think two lanes going from 6-12 on the clock, with single lane road at 3 & 9)
In the UK, we don't normally have stop signs, as most junctions have clear rights of way (https://www.rac.co.uk/drive/advice/road-safety/uk-road-marki... see "Give way to traffic on major road") In suburban roads, roundabouts are often used instead of stop signs. It allows much freer flowing of traffic in both heavy and light traffic.
Just don't look up the magic roundabout, thats just fucking batshit, we only have one. The reason why they keep it is because there is literally nothing else interesting about the place.
> Just don't look up the magic roundabout, thats just fucking batshit, we only have one. The reason why they keep it is because there is literally nothing else interesting about the place.
I was under the mistaken impression that Swindon was the only place mad enough to have magic roundabout, now I learn that H. Hempstead of Hertfordshire has one as well. bloody new town with their fancy town planners.
> they include rather obscure rules as to which lane you are allowed to drive in at any moment and americans do not like to learn new rules.
Do they?
I guess it probably depends on the country. Here in Sweden I'm pretty sure you can drive in whatever lane you like (unless they're explicitly labeled). But normal lane-swithching rules apply ofc and, importantly, when you enter a roundabout you have to yield to traffic in all lanes of the roundabout, not just the outermost one.
Yeah here in Australia, 2 lane roundabouts usually require that people taking the 1st exit use the outermost lane and people using the 3rd+ exits use the inner lane of the roundabout. (And if you’re going straight you can use either). If you’re in the inner lane of the roundabout and want to leave, you usually don’t change lane while in the roundabout, but signal and exit by cutting across the outer lane on your way out.
> but signal and exit by cutting across the outer lane on your way out.
That's how most of the multilane ones are are in my part of the US, and that's what makes them terrifying to me. It requires too much trust that the other drivers are going to do the right thing.
Not necessarily. Some roundabouts have the center circle partially paved so that oversize loads can drive right through if needed. There are curbs, speed bumps and road pillars that make it obvious for normal traffic not to take the shortcut.
It also doesn't fully protect vehicles already inside the roundabout. My father got rear-ended once while inside a roundabout by a possibly distracted driver and the car was a near write-off.
The main advantage of roundabouts is traffic fluidity. When compared to intersections with stop signs or traffic lights, unless it is full you can often enter a roundabout without coming to a complete stop first.
> Some roundabouts have the center circle partially paved
This is the "truck apron". Virtually every roundabout in our town has one, and it's up a little curb to get onto it. A little too much for cars to sensible abuse, but a dirt motorbike gets over them easily. :) Also when it snows in people can't tell where the apron starts, so traffic tends to cut over it.
The protection is just by hiding half of the traffic beyond an obstacle, you can still get t-boned on the roundabout, but only by the cars from your right and not from both directions like on an intersection. I guess it's a plus but with the added danger of a head-on collision from people traversing the roundabout in the wrong way I won't say if it's net-positive safety-wise with any degree of confidence.
I, on the other hand, have seen much fewer people running red (and that only when the red just switched on, without any cross traffic yet) than people taking left on a roundabout. So by your own method you can ignore people running red light on an intersection?
I have seen two cars but we have an extraordinarily amount of roundabouts so plenty of samples. Those two was in a roundabout that is a bit straighter than normal roundabout so it is possible to turn the wrong way without too much hassle but you still have to be pretty unused to roundabouts to manage it.
It also greatly reduces the impact of being t-boned by cars coming from the right. The car coming from the right has to slow down in order to take the roundabout. This means you are now getting t-boned by a car going 30mph rather than 60mph, which is the difference a fatal accident and walking away with barely a scratch.
Cars going the wrong way is a non-issue. It is clearly signed how you're supposed to drive, and if they constructed it properly going the wrong way means you have to do a left turn of about 120 degrees. It feels so unnatural that you'll have trouble doing it on purpose, let alone accidentally.
> The car coming from the right has to slow down in order to take the roundabout.
Why? We are talking about people, who don't pay attention and drive through an intersection, the same people won't pay attention and won't slow down, let pedestrians to cross and do other silly things in the video.
> It is clearly signed how you're supposed to drive
I don't know where you live, but roundabouts near me have no signage of any kind. They are intersections with the center removed, on one near my home I've been seeing the same woman doing a left turn once a week (we seemed to have the same schedule so going there around the same time). Not to mention that many people don't pay attention to whatever signage you will put up, it's not a magic spell.
Why? Well, because it should be physically impossible not to. A roundabout forces you to take a sharp right turn, with a small turning radius.
It's like turning right at a T junction. You simply can't do that at high speeds because you will flip your car. Most drivers have enough self-preservation to prefer slowing down over crashing their car.
I have a $6000 bill to show you for a physically impossible Toyota driving into my passenger door on a roundabout. A roundabout is just collection of T-intersections, nothing forces you to take right turn, you can drive straight, right, or left, physically.
And as for the self-preservation, running a red light on a normal intersection is doubly dangerous as you are risking both frontal and side collisions from both sides, if self-preservation is how roundabouts are safer then a normal intersection is doubly so (it is not, people who cause accidents are not guided by self-preservation).
safety? bah! try going round the hanger lane gyratory system (west london, uk) in a triumph spitfire, at high speed, driven by a girl (my girlfriend at the time) who was too tiny to reach the pedals.
Here in France they have both types of roundabouts, yield-to-left-on-entry and yield-to-right. They are well signaled, so there is no confusion. The latter type is less common and seems to be mostly in less-busy areas. I'm not sure why they still use them though. Is it because you have better visibility to the right, since you're already in the intersection? It's an interesting design choice.
I think the yield-to-right ones are primarily a traffic calming thing, where the threat to yield limits how fast you can comfortably go through them. They use a lot of yield-to-right intersections in residential areas with poor visibility for the same reason. It's conceptually similar to the 4-way stops on low-traffic streets in the US, just streamlined and formalized.
Personally, I'm fine with the simple single-lane roundabouts. They're convenient for U-turns, for example.
For anything above that where I have to cross lanes to get to the center circle and then cross lanes again to get back out and exit, I'd rather just have a conventional traffic light-controlled intersection. (I try to minimize lane changes when I drive.)
They're perfect for crossings with low to middle traffic. No useless waiting time, good visiblity and no need for traffic lights.
For heavy traffic, though, they're useless as the car flow of one entry/exit can take over the roundabout and block all other entries.
Also, it seems hard to understand for many drivers that regulations regarding changing lanes don't change in a roundabout. So more than 3 lanes are not advisable in my opinion.
So if an intersection is (e.g.) four-way, and one particular entrance monopolizes things than it can be given red at times and the others green (and than one-green/three-reds).
See (e.g.) "Performance and Safety of Roundabouts with Traffic Signals" by Tracz and Chodura:
> The paper presents designs, advantages and some drawbacks of various layouts of roundabouts with traffic signals, used in urban arterials on crossings with large traffic volumes. The authors analyze signal settings with alternative phasing used at intersections that can provide the intersection capacity of about 6500 veh/h in 2x2 lanes arterials or even 8000 veh/h in 2x3 lanes arterials. Accident statistics for roundabouts with traffic signals in Krakow are also given and discussed. In addition, presented are practical examples of changes of signalized roundabouts geometry; reconstruction into a form of turbo- roundabout and its effects regarding traffic safety and good performance.
Inside cites, those traffic lights in intersections were usually also semaphores for pedestrian crosswalks. So when you replace the intersection with a roundabout, you usually keep the traffic lights for the crosswalks alone. At the speed a car exits a roundabout, a non-regulated crosswalk could be quite dangerous.
Learning to handle a 3-lane wide roundabout outside Inverness Scotland, in right-hand-drive (that I only had 2 days of experience with) in full rush-hour was pretty fun.
There is a sign board which tells whether to take the middle road or left [1]
This is the round-about layout [2]
None of the above tell the precise lane to take. Only when you enter the roundabout you will know. See.[3]. Imagine cars waiting on these markings. This is what frustrates me the most.
My city has a lot of large roundabouts and a few years ago they made big improvements that reduced the number of incidents and improved traffic flow:
1. They switched from 3 lane traditional to 2 lane spiral roundabouts. There are signs well before you enter the roundabout telling you what lane you need to be in, so you can get into the right lane early. We have a lot of snow in winter, so road markings are not visible.
Example of a sign indicating which lane you need to be in. After this sign, there are two more signs indicating lanes before you get to the roundabout - the next has destination names.
2. The lanes on the roundabouts have solid white lines which you must not cross. You can only cross lanes to go more towards the center. I'm surprised, but people actually follow this rule.
There are "traffic circles" that aren't roundabouts but just a round block in the middle of an intersection that requires the traffic to move around in a circle so cross traffic is slowed. Also called a "traffic calming circle."
Roundabouts have to have splitters and other features that traffic calming circles lack. Also, technically you can go whichever way you want around a traffic calming circle: counterclockwise is recommended, but many trucks physically cannot navigate them that way. And there are zero traffic laws distinguishing a traffic calming circle from an uncontrolled intersection.
I am American! Metro Detroit area. I guess we also don't have many roundabouts. A lot of our road designs are based on Michigan Lefts[0] though which Wikipedia says are also called "median U‑turn crossover or median U‑turn, or restricted crossing U-turn (RCUT)" which I don't see much elsewhere in the country.
> Also, on the small side where you have traffic circles rather than roundabouts, those also suck.
Interesting. Can you elaborate? We have a few of them (and growing) by me and they’re fantastic as far as I can tell. No stopping every block for stop signs, I’ve seen landscaping truck with trailers sneak through them fine, and it’s so much easier on a bike or while walking. What’s the downside?
Correct me if I'm wrong... but compared to a traffic light, you have to go significantly slower, so most accidents are not as severe as at a traffic light. You also aren't crashing into someone in a t-bone situation, usually they are sideswiped at more of an angle for less impact force. Of course someone could still fly into a roundabout at full speed. Anything is possible, but feel like think overall there still have to be benefits.
People generally don't slow down for lights, and lots of times accelerate to make it through before it turns red.
Correct. Anyone that says roundabouts are less safe doesn't have science backing their claim. While, they do not reduce the number of accidents and in some cases can increase accidents, but they consistently reduce the severity of the accidents.
A three lane roundabout may be annoying when encounter as a tourist but the majority of locals going about their daily commutes quickly master them. For a three lane roundabout the inner lane is left turn only. The inner lane is left turn or straight and the right lane is right turns only.
The ones in my area have ample signage indicating which lane allows for each type of turn.
I would argue that the safety stats for them are still excessively car-centric. That is to say, roundabout collisions have better outcomes for car occupants specifically because they turn crashes into the kinds of crashes that cars handle best, which is low speed rear-endings, with the crumple zones doing all the heavy lifting to protect occupants.
I’m much more skeptical about how roundabout users fare when they are people walking or riding bicycles. At least in my city, we've had roundabouts for years, and the yield rate for pedestrians is ghastly— like, sub-50% of drivers stopping for someone waiting to cross and remaining fully stopped until the person is completely off the roadway. In theory this is a fine of hundreds of dollars ("failure to yield to crosswalk"), but it appears to receive basically zero enforcement in practice.
As a result, the fancy multi use paths that accompanied our roundabout installations get little use, since it's obvious to anyone who tries them how dangerous and unprotected they are.
I'm both a car driver and a cyclist. There are a zillion roundabouts in the country I'm living in. This is my experience and I'd like to hear a traffic designer about it.
Roundabouts feel safer than a 4 way intersecting when I'm in a car even if it's annoying to have to slow down and accelerate again when there is very little or no traffic, which is normal in the countryside. It also consumes more fuel, wears the car, adds to pollution.
It's different when I'm riding my bicycle. Roundabouts put me closer to cars, especially if there are traffic dividers that force cars closer to the side of the road. Then cars are usually slower than a bicycle in a small or medium sized roundabout (think of race bicycles with drop bars,) which adds up to chances of being packed between two cars. My feeling is that what's good for cars is bad for bicycles.
As a cyclist I can see what's around me much better than when I'm in my car. Intersections don't feel like a problem because of the extra visibility. When I'm riding I long for old times straight roads, with a line on the side and half a meter of asphalt on the other side to ride on. No roundabouts, no speed bumps especially the 3M style plastic ones, which I can jump but they are annoying. All those safety devices, including roundabouts, increase fatigue and danger. They are also the main reason for crashes in bicycle races but that's not an issue for normal people.
Finally, as I both drive and ride I know how to behave not to put in danger the cyclist. When I drive I don't overtake bicycles before a roundabout because they'll be at least as fast as me. I don't overtake when there is a short traffic divider which narrows the road. A long one, oh well, I have to. Same thing when I approach an intersection where I have to yield or stop. Bicycles will be definitely faster there because they can look around better than me and decide what to do quickly.
When I ride and I'm approaching a roundabout or entering a short narrowing of the road I look behind me and if it's safe I lean a little to the center of the road to prevent cars to overtake when they'll be forced to come close to me.
"Researchers in Belgium found that single lane roundabouts without a protected bike lane increased crashes by 93%, while Danish researchers said roundabouts that did have separated lanes saw an 84% reduction in crashes."
Ah, those traffic dividers, clearly designed by people assuming that all roads should be limited access...
"All those safety devices, including roundabouts, increase fatigue and danger."
They literally distract from the traffic when you aren't in a little isolated house on wheels where people are prone to forget that traffic even exists. All those things designed to help getting a driver's eyes off WhatsApp require cyclists to get their eyes away from traffic.
On the topic of roundabouts, one thing I rarely see discussed (never?) is that traffic lights conveniently compress the vehicle stream into packets of high and low intensity, greatly helping smaller intersections downstream. Roundabouts on the other hand flatten the vehicle frequency and of there's a difficult place to enter or cross the stream, even a modest amount of traffic can be too much. In the end everything that isn't a roundabout can only be navigated by relying on someone in the dominant stream showing off compassion with those waiting. This makes everything go even slower and you quickly end up with even dominant streams going less than walking speeds.
I have a hypothesis that roundabout-dominated road graphs are particularly prone to effective throughput dropping once a certain threshold of throughput demand is reached. Traffic light dominated graphs are immune to this if drivers are just a little careful to not enter an intersection before they can assume that they will be able to leave before the lights change.
That is a good point. In the UK when I was last there they needed all sorts of tricks to get people to slow down on roundabouts on A roads or just after a motorway end, going from say 70mph to zero.
You might have a curve leading up to the round about plus roundabout signs, plus give way signs, plus 300, 200, 100 yard markers, plus painted lines on the road that get closer together as you approach, and finally the <<<<< sign on the roundabout itself.
While you're here, can I ask you a question I've always wanted to ask about traffic circles? Perhaps this is also related to why they suck for safety.
At least where I live, there are two rules for traffic circles: (1) yield to traffic that is already in the traffic circle, and (2) when two cars arrive at the same time, yield to traffic on your right.
Rule 1 is the same as for a roundabout, but rule (2) is a bit strange when the two are put together. It creates a scenario where if the leftmost car doesn't yield for whatever reason (perhaps they thought they arrived a microsecond earlier), then now they move forward and become "traffic in the traffic circle", which means they steal priority and the right-most car now has to yield to them. If the rule were flipped the other way, such that we default to always yielding to the car on the left, then this wouldn't happen; it would work just like a roundabout, and the order of yielding priority would be the same regardless of agreement on the exact timing of when each car arrived at the traffic circle.
So, why is it that at a traffic circle we yield to traffic on the right, rather than the left? Is it just to be consistent with 4-way stops?
They added some circular medians in the middle of 4-way stops where I live, are those traffic circles? Are you suggesting that when I get to a 4 way stop, whether I yield to traffic on the left or right should depend on whether the intersection has one of those medians in the middle?
Personally I find it confusing that yielding works the opposite way on roundabouts and 4-way stops, and nobody else in my neighborhood seems to know what to do either. Whether people yield to me seems to depend mostly on the size of the vehicle I am driving.
Sweden treats the roundabouts as it's own road. To get into the circle you yield to whatever is inside the circle. The cars inside the roundabout is on their own road so only yields on lane change from inner to outer lane. When exiting they are leaving the road and is yielding to any pedestrian/bicycle crossing directly after the roundabout. Well, they are supposed to do but mostly don't.
There are a few non-standard roundabouts that has no yield sign and the lane goes straight into the roundabout but then it usually doesn't have an outer lane before that entrance.
I think you're right about single vs. 2+ lanes. It doesn't matter how many diagram signs they put up before the roundabout entry, people will NOT understand a roundabout with more than one lane, and under no circumstance will people going straight through realize they have to yield to someone coming from the opposite side who's going 270° around the circle and exiting from the inner lane.
Roundabouts are fine if the rule is, "Just get in there without hitting anybody and go around until you're ready to leave," but expecting anything more than that from most drivers is a lost cause.
Not sure exactly what you mean by freely, but in most popular roundabout designs you can exit from the inner lane. A "standard" two lane roundabout will have two lanes entering AND exiting. You never change lanes in roundabouts, at least where I'm from. Only in a massive multi-lane roundabout (that's at that point more like a ring road) would you ever change lanes to exit.
e.g. for a standard two lane roundabout with four exits, if you enter in the left lane, you can exit directly out of the 2nd, 3rd, and 4th (i.e u-turn) exits, but always in the left lane of the exit. If you enter in the right lane, you can exit out of the 1st or 2nd exits, but always in the right lane of the exits. With this design cars travelling alongside you can never cross your path, only cars entering the roundabout ahead of you can cross your path and it's their responsibility to yield.
The thing that most often causes problems is people in the outer lane NOT exiting (e.g. thinking they can take the third exit from the right lane) and swiping the car in the inner lane correctly taking the second exit.
The car from the inner lane swiping into the car in the outer lane is the exact issue I'm talking about. The problem is when drivers enter in the left/inner lane, fully intending to take the first exit. If they proceed to exit directly from the inner lane, without first changing lanes, signalling, or yielding to outer traffic, they would intersect with a car in the outer lane innocently heading to the second exit.
In practice, people are not able to navigate two-lane roundabouts in a compliant and safe manner. Any intersection of roads busy enough to have two lanes in each direction is too busy for a roundabout to be safe.
It’s still safer than a normal intersection.
Roundabouts prevent HIGH SPEED t-bone and head-on collisions.
The difference in safety is easily worth the “cognitive load” of a 2-lane roundabout.
I think drivers will get used to them and in practice there will be few collisions.
> I think drivers will get used to them and in practice there will be few collisions.
I think drivers will avoid them at all costs since even low speed collisions can cause extremely expensive repairs (and even total an older vehicle) meaning they'll never get the practice they need to navigate them safely, yet eventually those drivers will find themselves in a situation where a roundabout can't be avoided and suddenly it's chaos for every car in the intersection.
Even if multi-lane roundabouts were suddenly everywhere we'd probably need generations of new drivers trained to use them in drivers ed classes as teens before you could just trust people to be able to navigate them correctly
> The problem is when drivers enter in the left/inner lane, fully intending to take the first exit. If they proceed to exit directly from the inner lane, without first changing lanes, signalling, or yielding to outer traffic
Yes, in that case a driver not understanding the rules of the road (that you can't take the first exit from the inner lane, which is usually clearly signed) could cause an accident. The exact same way turning right from the left lane in a signalized intersection can cause an accident. The question is, what's the damage of an ignorant driver and how fast do people learn? The research indicates that right-of-way incursions in a roundabout result in dramatically fewer injuries than right-of-way incursions at other types of intersections, and the research also indicates that contrary to your belief, drivers actually do learn how to use them.
They are right to. Simplified greatly, the further in the roundabout you are, the right of way is yours.
The exception is you can obviously not shoot straight from the left lane to the first exit.
In a 2 lane roundabout it is very simple. Enter in the left lane and you can exit 2nd or 3d, enter in the right lane and you can exit 1st or 2nd.
Where it gets complicated is roundabouts with 2 lane entry but only 1 lane in the third exit. Then you have to change lane right halfway through and be careful with people entering prematurely from your 1st exit, or people incorrectly staying in the right lane past the 2nd exit. It’s not always obvious but for those entering the rule is the same, since they enter after you, they should yield to you.
I guess this is depending on country. In Sweden you are allowed to exit from the inner lane. But you have to yield to traffic in the outer lane because you are doing a lane change even if you go straight for the inner exit in a two lane exit. The outer lane is not causing the accident, they do not have to yield and they are allowed to go to the third, fourth or fifth exit fully in the outer lane if they want to. You just have to make sure you don't hit them on the way out.
This however does not stop accidents to happen all the time in this situation because of drivers trying to get past the traffic jam by going inner lane in high speed and then exit in front of traffic trying to get to next exit. And mostly without blinking at all.
Our town has loads of them too, and everyone think they understand them. Still accidents are common because people think it's ok to just go straight through by changing lane to inner and then directly exiting without yielding to the ones crossing their path in the outer lane.
We have quite a few without curbs too, but they usually have markings for what lane is for what direction and are "skewed" so that you don't normally have to change lanes.
Honestly, even looking at a picture showing how a 2-lane roundabout works (https://www.epermittest.com/drivers-education/roundabouts), I still can't understand how it works. Assuming 0 is the bottom and 90 is the right, how is it that a person following the inside route from 0 (exiting the left lane at 180) isn't going to get hit by someone following the outside route from 90 (exiting the right lane at 270)? I would almost certainly use it wrong and/or expect to get hit.
The "correct" answer is the 0->180 car has no indicator on as it enters the roundabout, and has its right indicator on as it exits the roundabout.
The 90->270 car sees the right indicator and lets the other car passed.
The real answer is somewhere between the above and the 90->270 car waiting to enter the roundabout because it is not sure if the other car is actually going 0->180 or 0->270 because they are a shit diver that doesn't indicate on roundabouts.
well, that breaks all schemes, as my experience in 52 years is, that most people don't or won't operate their indicator signals properly. They seem to believe they are for special holidays, or for a particular audience they have spotted (spoiler alert: they are for the opposite).
Or, my favorite: Activating the indicator two thirds of the way through the already completed turn, presumably to celebrate the success.
The part you're missing is you have to yield when changing lanes, just like in any other road. If you are in the inner lane and you want to exit, you have to make sure the coast is clear. In other words, you are responsible for not getting hit. If you just blindly change lanes you might get crashed into and that would be your fault.
> The part you're missing is you have to yield when changing lanes, just like in any other road.
This is not true with most roundabouts in North America at least. If you look at the diagram GP posted, you do not change to the outer lane to exit. You exit directly from the inner lane. In fact, you NEVER change lanes in a roundabout. The reason this works (where the inside lane crosses the outside) is because the roundabout is small enough that the traffic in the outside lane has to let you exit as part of yielding to enter the roundabout in the first place. After that, as long as everyone respects which exits they're allowed to take from which lane, there is no more crossing traffic. In practice, if you are in an inside lane, you want to keep an eye on the outer lanes to make sure someone isn't trying to take a later exit than they are allowed.
From GP link:
> Do not change lanes in a roundabout
> Do not travel in the outside lane further than allowed as it may create a hazard for the vehicle exiting the roundabout from the inside lane
That doesn't work. If I enter a 4-way roundabout going left, I will start off in the left lane. I will pass two exits and leave through the third. When I exit, someone from the second exit could be in the lane next to me, going to the road I came from. I have to yield.
When you exit from the inner lane you necessarily have to change lanes because the inner lane is completely inside the outer lane. You may not think of it as a lane change because you're going across the lane not merging into it, but it is a lane change and you have to pay attention.
> I will pass two exits and leave through the third. When I exit, someone from the second exit could be in the lane next to me, going to the road I came from. I have to yield.
No, they have to yield to YOU because you're already in the roundabout. It's hard to believe, but trust me, this is just how it works and all of the links I've posted agree. The reason why it works is because when you're in the situation you describe, for the person entering at the second exit to be a factor, they would have to be entering as you're already alongside the second exit and in the process of exiting at the third. So they need to be yielding to you as they will be crossing your lane. Part of waiting for the gap is waiting for the exiting traffic to clear. Not for only YOUR lane to be empty.
> With multi-lane roundabouts, it is important to stop for vehicles in all lanes of traffic. Wait until there is a gap in all lanes of traffic and then enter slowly. Never try to enter alongside cross traffic or assume any driver's intended path. One of of the most common mistakes people make when entering a roundabout is failing to yield to all lanes of traffic. Yield doesn't mean just slow down or merge. Yield means that you must wait until all traffic in the roundabout has cleared before proceeding. Make sure that no one is in either lane of the roundabout and then proceed.
The video also has a good overhead view that is better than most at showing the scale of the roundabout. The important thing to note here is that to enter the roundabout, you have to cross the lanes that are exiting, not merge into them. So you are yielding to all exiting lanes.
> Assuming 0 is the bottom and 90 is the right, how is it that a person following the inside route from 0 (exiting the left lane at 180) isn't going to get hit by someone following the outside route from 90 (exiting the right lane at 270)?
The person following the outside route from 90 must yield before even entering. It's very confusing until you're actually in them, but they're small enough that what you're saying usually isn't really a problem (at least in well designed roundabouts). When the car at 90 enters the roundabout intending to take the 270 exit, they yield to traffic in ALL lanes that might be exiting. Not just traffic in the outer lane. If they were intending to take the 180 exit, they only need to worry about traffic in the outer lane (or people incorrectly changing lanes when exiting).
I agree, Australian cities seem to think that they solve every traffic issue. There is a double lane less than 200m from my house.
The shitty part about roundabouts is when people allow blocking of the view to the right on the round about so you are unable to see incoming traffic till its almost on the round about.
Traffic police here in Romania had to actually add some stuff to the legislation that would make 2-lane plus roundabout traffic easier to understand, the reason being that the traffic policemen themselves had conflicting opinions about who had the right of way inside said roundabouts (when changing lanes, for example).
Where are you? We have tons of 2-lane roundabouts in Sweden as well, and I can assure you that far from everyone understands them. And even if they understand them in the sense that they got the theory question about them correct on their driving test, everybody certainly doesn't implement that knowledge consistently and correctly when faced with a 2-lane roundabout.
Bratislava, Slovakia. I don’t recall anyone I know having an accident on a roundabout.
Newbie drivers I talk to/drive with are much more worried/unsure about crossings (both the ones without traffic lights and the big ones with many lanes) and of course about parking.
Of course, there will be SOME people who are clueless on roundabouts, similar to how there are always some people who will stop on a highway after missing an exit and pull back. But let's not argue about the long tails.
IMO if you learn to drive at a time when roundabouts are already ubiquitous, they are trivial. At least I found other aspects of driving more difficult.
> there are always some people who will stop on a highway after missing an exit and pull back.
What?? People do that??
My mind is blown. I've never once seen that happen, so the possibility never entered my mind. Now that I think about it, though, I should probably be more surprised that I haven't encountered it.
There's lots of multi-lane roundabouts in the UK, and generally seem to work well, but they're often inconsistent with how lanes merge or depart.
One that gets me every time I go past is one where there's like 20 signs saying that both lanes continue to the main road to the right (270 degrees around, the UK so driving on the left), but I don't think I've ever been through there and not have someone try to merge in to me trying to get into the left lane to exit, despite both lanes leading to that exit.
I don't know what the letter of the law is but I (and most people I've seen here in Australia based on driving patterns) interpret yielding to cars on the roundabout as giving way if I will get in the way. If they're still on the other side of the island, and we can both pass through without getting in each others' way, it's fine.
Of course the de facto standard here (which many people actually think is the law) would be "give way to the right" (i.e. left for US) meaning some people will proceed without stopping even if the car to their direct left got there just before them. I think this is predictable since more risk falls on the driver who is going to get T-boned in their driver side door if they don't stop so they will be naturally cautious.
> expecting anything more than that from most drivers is a lost cause
I can't speak to the area you live, but where I'm from we get along just fine. Yes sometimes you still get the odd unfamiliar driver that doesn't understand them, but for locals there's a critical mass where roundabouts stop being avoidable and you adjust.
The big issue is that multi lane roundabout forces the driver to watch too many things at the same time while giving him very small margin of error. If you are not fast with reactions and aggressive enough, you can end sort of trapped in the inner lane and people are afraid to do one more unnecessary round.
And that means everyone has to watch both left and right at the same time while also trying to figure out layout (Will the outer lane force me out when I do not what to? Some roundabouts are like that. Will the inner lane keep me trapped? etc)
This. My community built training facilities. Didn't help much. Also, for new drivers these just induce anxiety and give them new opportunities to halt traffic and get horns blasted at them.
> It doesn't matter how many diagram signs they put up before the roundabout entry
It doesn't help that often those signs are pretty confusing all by themselves (at least the ones I've seen), and can't really be grokked from a brief glance driving by.
It would be better if all such roundabouts were consistent in how you should navigate them, but that isn't the case in my area.
> Multi-lane roundabouts don't typically have any safety benefits.
There seems to be quite a bit of literature that flatly disagrees with this statement. Perhaps you could add a source? The conventional wisdom where I'm from is that multilane roundabouts don't reduce the absolute number of crashes (and might even increase crash rates), but they still dramatically reduce the severity of crashes.
Canada:
> However recent data in the United States and Canada are showing that collision frequency at multi-lane roundabouts is often higher than expected, and sometimes higher than the prior signalized intersection. This trend is worrisome given that roundabouts are often constructed as a means of increasing safety. The good news is that fatal and injury crashes are almost always reduced with roundabouts, even if property-damage-only crashes are not.
> Multi-lane roundabouts. These are less safe than single-lane roundabouts, but still safer than other types of intersection [22]. Multi-lane roundabouts are less safe because they have a larger number of conflict points, they are more complex, driving speed is higher, and they have a less sharp entry angle [23].
> Roundabouts force drivers to slow down and all but eliminate the most severe types of intersection crashes — right-angle, left-turn and head-on collisions. Single-lane roundabouts see fewer total crashes of any type.
All roundabouts prevent vehicles from just blowing straight through the intersection in the desired direction without so much as slowing down. They remove the middle part of the intersection where conflicting paths intersect.
Two-lane roundabouts are larger; cars go around them faster. There is ambiguity. Some cars short-cut using the middle lane, and veer right out of it to their desired exit. Cars in the outer lane might be wrongly assumed to be turning off at the next exit. North American drivers get really confused by two-lane roundabouts.
I don't think these situations will typically lead to anything worse than fender benders.
The same intersection without a roundabout could be host to fatal collisions, when two vehicles enter at speed and hit each other in the middle.
> All roundabouts prevent vehicles from just blowing straight through the intersection in the desired direction without so much as slowing down
Not at all. A large enough roundabout with good visibility from the approach can allow you to traverse it without slowing down at all - if the speed limits coming up to the yield line are appropriate, and traffic is flowing.
There's a sense in which a roundabout is just a short circular section of highway with a series of on and off-ramps around the edge. Well designed onramps allow you to merge without slowing, and off-ramps let you leave without disrupting traffic. Roundabouts can permit the same.
> I don't think these situations will typically lead to anything worse than fender benders.
Since even a fender bender can cost many thousands of dollars in repairs that's still pretty terrible. Speed bumps slow drivers down too and don't risk people turning into you because they were trying to exit from the inside lane of a roundabout.
s/because they were trying to exit from the inside/you were trying to outrace them in the outside lane/
The two lanes are there in larger, busier roundabouts to reduce collisions, not for "slower traffic, keep right"; it's not a freeway. Cars enter the outer lane, and may use the inside lane to avoid other cars entering.
This is a problem with all multi-lane layouts and exacerbated by drivers' behaviour.
The problem is road users new to the road do not know which lane to be in already and they are pressured to go fast. The instant it looks like they've chosen a lane, a driver from behind who is familiar with the layout closes the gap in the other lane, trapping them.
This can be mitigated a bit by the first user having the confidence to slow down and straddle lanes until they are sure of the correct lane, but it's surprising how quickly such opportunities are missed.
The real problem is familiarity with lane layouts allows the road to operate at far higher capacity then normally possible and with less maintenance. They are squeezed to their limits in morning rush hours comprised of mostly familiar users. You'll even see users observing essentially invisible road markings because they're doing it from memory. No chance of you're unfamiliar with the road. Roads start to fail way before 100% capacity, but these lane markings allow that to be squeezed further during rush hours.
It's not a big problem to be in the wrong lane. You just change lanes like any other road. And like any other road, when you change lanes, it's your responsibility to make sure the lane you're merging into has space for you.
Driving schools in UK teach that changing lanes on a roundabout is unsafe. Infact, in a driving test doing so will result into a failure because most people will not follow safety checks and signalling.
If you are in a wrong lane, the safest thing is to continue on it, exit the roundabout and comeback again or go around the roundabout.
Perhaps you've never driven so I'll give you the benefit of the doubt. Cars can't move sideways. To change lane you have to go forwards. There is no "just change lane".
Of course you could just not change lane, to the wrong way and safely correct your course later. This is preferable but people tend to get stressed out in those situations which is also bad for safety. Not to mention that a safe but ineffective road hasn't really achieved much.
Oh yeah I was totally suggesting that you should stop the car, turn all 4 wheels 90 degrees and drive sideways into the next lane. That is exactly what I was suggesting. /s
I won't bother trying to expand on my comment to you, you're clearly not someone I'll be able to communicate comfortably with.
Coming out of Oxford on the A4144 there are two lanes; the left lane is for taking the first two turns and the right lane for the remaining three. But, drivers unfamiliar with the layout who haven't seen the markings, or who fancy jumping the queue, will sometimes use the left hand lane to go straight ahead onto the A44. There's a similar situation coming from the A40 to the East.
I've seen a few accidents there and even been involved in one as a result of this (someone tried to undertake me at speed as I exited, and caused a collision, 100% their fault according to our insurers).
Yeah, I never understood why the lane markings are not above the head and in advance instead of on the road.
> drivers unfamiliar with the layout
People familiar with the layout drive even when the markings are completely faded. It causes lot of anxiety if you are not familiar. It happened to me once where I was in a wrong lane. I continued on it as it was the most safest thing to do but the next exit was onto a motorway :). I was so angry with myself.
That Oxford example, at least, does have a "get in lane" sign[1] as you approach up the Woodstock Road, so any driver intending to go straight ahead on the A44 should know to use the right-hand lane to enter the roundabout.
But of course not everyone notices every sign (and some drivers just wilfully disobey them if they think it'll save a few seconds...)
Two-lane roundabouts still confuse me a bit. Even the video tutorial in that article has what looks like a problem to me. At 1:06, the pink car in the right lane skips the first exit. How does the orange car in the left lane know it's safe to take the second exit? That's a collision risk right there if the pink car wants to continue counter-clockwise.
The pink car is in the wrong lane if it wants to stay on the roundabout for a later exit. The pink car can take either the first or second exits here. The orange can take the second, third, etc.
It is now considered that multi-lane roundabouts (which permit lane changing in the roundabout) are a bad idea because they have too many collision points. Turbo-roundabout is a much better alternative: https://en.wikipedia.org/wiki/Roundabout#Turbo_roundabouts
Multilane roundabouts in my part of the US are absolutely terrifying because people don't know how to use them. Accidents and close calls are amazingly common. As a result, I drive out of my way to ensure that I avoid them.
As a bicyclist, I avoid multi-lane roundabouts like my life depends on it... because it does. Utterly nightmarish experience. This is why I despair every time someone is like "let's build more roundabouts in the US!" No, what you're missing is that all our roads are already too wide and all we get are multi-lane roundabouts, which are worse than intersections. At least at an intersection, I can see that one lane of traffic is already stopped, and know that it would take at least a moment to accelerate before hitting me.
I bike as my primary transportation, and there's literally no chance that I'd dare to bike through a roundabout. Seems like a recipe for serious injury or death to me.
Fortunately, I live in one of the few US cities that really are bike-friendly, so 90% of the time I'm on a bike path that is physically separated from where cars go.
Long time Carmel, IN resident here, AMA. Yes, almost every intersection has a roundabout for a population around 100k. Yes, they are efficient. Yes, it’s a pain using them when people who don’t know how to use them, use them.
Checking in from WI here. We started getting a lot of them in the greater Green Bay area about a decade ago. It's better-ish lately, but there are still consistently issues with drivers who don't understand how they work, and there are frankly too many of them located around light-industrial areas. I have no idea how these get approved for those locations: for commuter cars, they're excellent. For LTL trucks, they are highly problematic, cause traffic backups, and due to the nature of those large vehicles, basically the only way they can proceed through them is to wait until there is no traffic at all in any direction, or simply pull forward and hope the driver in the roundabout can/will stop in time to avoid an accident.
It's also worth noting: this are notably more difficult to traverse during fresh snows. While starting and stopping is certainly an issue in snowy intersections, a roundabout introduces a lot of turning, and especially so in cases of spiral ones. Two-lane roundabouts basically have to become one lane during a heavy snow, there just isn't enough grip to safely maneuver one with multiple lanes. And that's with Wisconsin lanes, which are notably large among US states.
> Yes, it’s a pain using them when people who don’t know how to use them, use them.
Here in Michigan there are roundabouts everywhere. And I'd estimate oh maybe 20% of the drivers know how to use them. Because of that, I absolutely hate them.
A roundabout around here is just a total luck of the draw on what you will get: people treating it like a four way stop, people ignoring it completely and just blasting straight through at top speed, people going into the roundabout then stopping at every merge point, people going into the roundabout and stopping to let someone else merge in front of them, on and on. I'm still amazed at what people do.
I suspect the people who blast through it at top speed and cause an accident cause other people to turn into the type that treat roundabouts with extreme caution.
Just outside my neighborhood I must have seen 10 accidents in the past two years alone. That's a lot of accidents at an otherwise low traffic intersection.
I love roundabouts. Driving in the UK is a revelation. You just sort of keep going and driving is a bit more fun. The drivers are also better than in the USA. Which is why I think there’s often resistance here.
Every time a roundabout is proposed near me there’s a vocal group of opposers. I just don’t really get it since in many cases a roundabout is preferred to an intersection in my opinion. But one comment I read summarizes it I guess:
“Drivers here are just too dumb for a roundabout. We can trust them to think.”
And I guess I sort of agreed. Driving in America is weird because so many people do things like passing on the right, not using turn signals, and driving the wrong speed in whatever lane they’re in causing chaos.
What confuses me on roundabouts is the intended speed. Some are very tight and requires slowing down to 15mph and others can handle faster speeds. Rarely is the intended speed marked.
A new roundabout in Brevard, NC has a very tight turning radius. There is a sign warning drivers in the outer lane to watch out for tractor trailers who will have to take both lanes to navigate the circle.
Yes, some residential ones are absurd. This one would've been better as a 4-way stop because there's no way to see traffic from all other sides due to the angles and obstructions. https://maps.app.goo.gl/GWoqaxNfVanXLymp6
One went in here where people normally drive 60 mph:
On Clark straight through, I would look for approaching traffic from either side or ahead and would cut across the hatched area, mostly maintaining speed. It's honestly better than stop signs or stop lights.
The first one is totally fine. When you're entering the traffic you're driving at about 15-20mph due to the sharp curve forcing you to, so there is plenty of time to look for traffic already on the roundabout coming from your left. With the exception of the signage, I'd say this is a textbook example of a roundabout done well.
The second one is a bit of a mess. The fact that it is physically possible to take them at 60mph means they screwed up the design. They should've used something like slightly raised cobblestone for the hatched area, and they should've used a raised shoulder at the entrance/exit. This roundabout looks like it was designed by someone who has only ever seen it in a textbook, and never actually driven on one.
Roundabouts for high traffic areas are good. The problem is when they are overused in low traffic areas where they create obstacles to efficient continuous motion, increase pollution, and waste time.
PS: One place that doesn't do proper traffic design (or architecture): Texas. They insist on placing massive concrete dividers everywhere and have camouflaged by wear obstacles in the middle of paths that are injurious to bicyclists. It's nothing like the Netherlands where there aren't many random, dangerous surprises.
> The problem is when they are overused in low traffic areas where they create obstacles to efficient continuous motion, increase pollution, and waste time.
The alternative (at least from my experience in the US) is a 4-way stop, and is worse for all those criteria.
Here's an explainer on "conflict points" [1] which seems central to the argument. Most folks intuitions are correct that roundabouts eliminate cross-traffic (major conflicts), but they also reduce merge, diverge and weave conflicts (minor).
Two lane roundabouts are pretty good. More than two lanes are very questionable. And roundabouts which include... stoplights!?!? are just stupid.
I live in the Netherlands, where roundabouts are very common. In many cases, they are an improvement.
But NL is also a huge bike country. And at most roundabouts, bikes have right of way. So as a car driver, you have to worry about other cars as well as bikes which may turn (go away from the roundabout) or continue (cross the adjacent road circularly around the roundabout.
In good visibility conditions, it's ok. And by OK, I mean it can still really f* up car traffic, especially when it is a high traffic area not far from a school. In lower vis conditions, and/or when electric higher speed bikes are concerned, it becomes a whole new kind of danger.
I would argue that the benefits of roundabouts diminish or fully disappear when the number of lanes exceeds 2, or when traffic lights are added to roundabouts, or (and!) especially when bike paths intersect with and circulate around the roundabouts.
> But NL is also a huge bike country. And at most roundabouts, bikes have right of way.
The fact that it's on a case-by-case basis an not actually a consistent traffic law is really awful. To add insult to injury, the only signage is usually a yield sign painted on the road that is invisible as soon as it's dark and the road is wet. And this is of course further combined with the absolute scandalous amount of cyclists who don't have lights at night and are dressed in fully dark clothes.
Roundabouts are already a traffic situation that require heightened attention as a driver, so in the interest of safety I believe crossing cyclists should yield to cars at the exit. It's too many things to worry about otherwise. But at the very least, make it the same everywhere so it's always absolutely clear to both drivers and cyclists who has the priority.
In built-up areas it's often (usually?) a bicycle lane, i.e. on the same piece of asphalt as where the cars are. In that case, bicycles always have priority. It's the same as taking a right turn: wait for bikes that go straight. Outside built-up areas it's always a separate bicycle path, often with some distance from the car lanes.
The confusion can arise inside built-up areas where there's a separate bicycle path, usually close to the car lanes.
Under light to medium loads, roundabouts are preferable to junctions with stop lights, as you rarely need to wait long to enter the roundabout. But under high loads, they can cause starvation when there are no breaks in traffic along the more major road, so traffic cannot enter from the side road. When that happens, you need to add traffic lights to allow traffic to enter from the side road. But the traffic lights can be set up to only operate at busy times, so then you get the best of both worlds. Traffic lights on a roundabout at quiet times - yes, that's just stupid.
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[ 4.0 ms ] story [ 305 ms ] threadThe De Soto Plaza in in Coral Gables, FL, built in 1925, as seen at https://www.google.com/maps/@25.7450124,-80.275242,3a,75y,75... is not a modern roundabout. Granada Blvd does not indicate a yield-to-enter, while the others streets have stop signs.
I think that one should also have splitter islands.
(Video of its history at https://archive.org/details/Did_You_Know_-_DeSoto_Plaza_Foun... .)
I think Cocoplum Circle might count as a roundabout? https://www.google.com/maps/@25.7059315,-80.2608362,3a,75y,1...
There are also "traffic calming circles", which are not roundabouts. "Traffic calming circles should not be confused with roundabouts, which are designed to handle much higher traffic volumes and reduce vehicle delay." - https://www.sfbetterstreets.org/find-project-types/pedestria...
> In 2000, the U.S. only had 356 roundabouts. Over the past two decades, that number has grown to over 10,000.
It's great news all over that the number is clearly increasing, but still a very long long way to go until it becomes widespread.
So 59 000 roundabouts for half the population versus 10 000 in the US.
That's a deficit of 90% per capita :-)
For my other Americans, read the Australian's post above. Can get across an entire town without stopping as a reason to remake our towns with roundabouts.
The us does not have loads of them they are few and far between
Four way stops do not exist (I've never seen one in all of Australia), and they are still the strangest concept for me living in Canada. They feel like a colossal waste of time and energy, and vastly worse than roundabouts.
Haven’t seen one anywhere else.
Apparently there was one in Rockingham, Western Australia, says https://www.news.com.au/technology/innovation/motoring/fourw... ("Four-way stop sign stumps WA motorists, brings traffic to a standstill") but it is not there now at https://www.google.com/maps/@-32.2753035,115.7324187,3a,75y,... .
They're so common in the US that 3-way or 2-way stops are often marked as such so that you don't make any assumptions about cross traffic stopping.
And please don't misunderstand me--I'm definitely envious.
https://www.google.com/maps/@42.3875777,-71.1422076,18z?entr...
this avoids complete deadlock until the entire roundabout is full of drivers who refuse to take any unblocked exit, while continually offering each the ability to do so
I don't understand how that helps. The problem is there are too many cars in the rotary, so no amount of not leaving the rotary will unblock it. It seems like you should not enter unless there's room to exit, but on some of these, you can't both see the exiting traffic light and safely merge into moving rotary traffic, so I don't really blame drivers who enter the rotary and find the light turns amber then red on them.
i could also imagine that anyone waiting behind someone who is deadlocking might have success sending a signal to the blocking process, unless they have committed to a non-reentrant exit routine
This can happen on routes where there are multiple chained roundabouts, that usually results in traffic coming at an even rate with no gaps in between.
Multi-lane roundabouts help when theres a clog downstream of the roundabout.
Roundabouts are also great if you have more than 4 roads meeting.
But yeah, in general roundabouts shine the most in low-traffic intersections that previously had lights. They make driving in those are so much nicer, drivers basically never have to stop.
Some cities in Europe have so many roundabouts, and two or three lane roundabouts with complex exit decisions you need to make on a split second - it's actually very confusing to navigate.
They decrease serious collisions.
and two or three lane roundabouts with complex exit decisions you need to make on a split second - it's actually very confusing to navigate.
I think you're confusing what today might be called a "rotary" (?) with a modern roundabout. Whatever you call it, I don't think anyone builds what you're describing anymore.
Because they don't remove the idiots from the roads. The same people who willfully ignore right of way at stops signs also ignore right of way in the roundabout.
Agree, when at or near 100% utilisation, its slower than a normal junction.
> you may actually increase the risk of collision due to negotiations about right of way happening every time a car can move forward.
That shouldn't be the case. Ideally you should always have priority from one direction (like in the UK, germany and the netherlands.) The generally rule is that when you come to the round about, if you see someone on your right(in the UK, left everywhere else I imagine) you stop and wait for them to drive past.
> two or three lane roundabouts with complex exit decisions you need to make on a split second
The driving exam will test you for this in the EU. The lane you chose is directly related to where you need to exit. If you are going straight over, or less, then its the outer most lane. Anything more than 180 degrees you take the inner lane. Exceptions will be clearly marked in both floor markings and signs well before entry.
This is near where I live and it is indeed safe, mainly because everyone drives incredibly slowly and cautiously since the experience is scary as hell.
Of course it's a real spaghetti intersection where you need to potentially navigate dozens of 2D roundabouts to get to any given direction. Which coincidentally also is true for the 2D road network where I live.
Bonus question: if you can, what happens if you drive a DeLorean at 88 miles/hour on it?
Every driver in the UK is used to sequences of two or three roundabouts, they are part of the driving test. As long as you are not bamboozled by the pseudo roundabout in the middle, you just navigate it based on principles you already know.
As other comments have noted, when drivers are less clear on the rules they tend to drive more slowly and cautiously - I think that makes double roundabouts "work out" most of the time.
Holders of foreign driving licences should probably be required to do a course, including these at least, before being allowed to use their licence here.
Apparently there are fewer accidents on the roads when the traffic lights aren’t working. The reason is exactly that - everyone is terrified and drives really slowly to make up for it.
We could accomplish the same with other forms of creative driver-hostile road construction and deliberately unproductive signage.
but if they aren't common, so you need to construct it in a way that requires compliance, more space is required
Roundabout with more roundabouts on it. Because.
Basically just a little ring road.
It is nice to not have to pay for replacement signals, or have to deal with power outages that kill the signals though.
Drivers anticipating their merge into roundabout are often too distracted to notice pedestrians intending to cross, and any pedestrian crossing the outflow of a roundabout can trigger a traffic backup that interferes with the flow of the circle itself and surprise drivers who expect it to stay moving.
They have their benefits in some intersections, but they also have tradeoffs that make them very poor for others.
I'm confused by your comment that drivers merging into a roundabout are too distracted.
As a driver merging into a roundabout I find I have far less cognitive load. I only have to look for pedestrians crossing in front of me and cars coming from the left. When coming off the roundabout I only have to check for pedestrians crossing the exit I want to take.
At an intersection, all these checks are mashed together into. I have to keep track of all the cars at the intersection plus the pedestrians that may be crossing in front of me and the exit I want to take.
Drivers coming into them, who want to actually benefit from the roundabout and not just turn it into an awkward stop sign, are responsible for reversing the exit to lane mapping, then timing their approach to the intersection with an opening that will let them reach to their lane while maintaining a flow. If they can't manage to do that, of course they're supposed to stop and yield until an appropriate opening becomes available.
Inevitably, the designated pedestrian crosswalk is some 5-10+ feet prior to where the car would have to stop if it does need to yield while awaiting an opening.
Compared to a signaled intersection or a 2/4-way stop, where the pedestrian crossing coincides with a natural traffic stop, this basically means that approximately zero cars actually stop for pedestrians. Some are too busy to notice and others just don't want to have to deal with a stop and so ignore their responsibility.
I assume you must live somewhere else, where roundabouts are smaller and play some different role than here.
I'd argue that 1 lane roundabouts are far from decorative in residential neighbourhoods and are safer and allow for a better flow of traffic.
I'm slightly confused by your description, but it sounds like traffic lights for the pedestrian crossings would be a better option (which is often the case with the bigger roundabouts in the UK). Are the roundabouts you referring to like this one https://maps.app.goo.gl/xfxzDWTx4a7WPasUA or smaller?
Excepting for single-lane roundabouts, I find they require a much higher cognitive load for me.
I find I sometimes miss pedestrians waiting to cross from the right, because I must look left to merge with oncoming traffic and it's hard to look hard left and to the right at the same time.
At a signalized intersection, if all parties follow the signals, there's often no situation where I'm supposed to be looking in both directions for conflicts.
If I travel straight through the intersection on a green light, there should be no conflict with pedestrians (although one must always be alert). There may be a stopped or slow vehicle in front if the exit is congested. If an unprotected left turn is allowed, I must be aware of that potential conflict while I traverse the first half of the intersection, and if right on red is allowed, I must be aware of that potential conflict as I traverse the second half of the intersection. It's of course useful to be aware of potential for other parties to violate their signals, but look mostly straight but to the left for the first half and mostly straight but to right for the second half works for turns and red light violators ... and mostly straight is pretty good for pedestrians crossing against the light.
For turns, pedestrians are in the same direction you're heading, and often the same direction you're looking. Right on red is an exception, but one typically stops behind the line and looks around for pedestrians before crossing the line and looking for an opportunity to merge in.
For safety, pedestrian crossings should be moved away from roundabouts, where drivers will see them better, but then that increases the path length for pedestrians and acceptance is low.
What I've seen first hand in Ontario/Canada is that there's a huge increase in cognitive load simply because the roundabouts are still fairly new. Most drivers were never taught about them. They've just appeared. And they aren't completely intuitive for many drivers -- so their entry/exit isn't always ideal/safe.
For one, both entering and leaving the roundabout happens at low speeds, so there's very little chance of getting hit at high speed.
Second, the drivers are necessarily doing turns, so their blind spots move around quickly, which makes it easier to scan the area for pedestrians.
This is so true that it happens constantly at a roundabout in my neighborhood that has stop signs and white stripes at the pedestrian crossing, right before the merge. Even people in the right turn only lane do it.
have you seen the mini roundabout yet?
people kind of follow the rules but sometime cut over the middle - especially on the very small ones
Well with a roundabout if you just go straight ahead you hit the center circle. Good roundabouts always have a slight hill and some kind of barrier (a tree or some kind of statue) in the center so that the guy that just goes straight through will hit something in the center and wont come out the other side and will thus be less likely to kill an innocent person.
Single lane roundabouts are usually a good idea if the cost justifies it. Double and more lane roundabouts probably should be avoided in the US; they include rather obscure rules as to which lane you are allowed to drive in at any moment and americans do not like to learn new rules.
She kept insisting I turned in front of her (technically true, I was in a roundabout). She was arrested for drunk driving, and, later on, fined for all the flowers she damaged in the circle and the median she also ran over on her way into the intersection.
Drunk drivers have launched cars into all kinds of random shit and places where you would not expect an accident.
Interestingly enough, a new roundabout was installed in my neighborhood. We considered something pretty to look at in the middle, but the city said no way. "Emergency vehicles need to be able to go through the middle at full speed". Meanwhile, busses have zero issues negotiating the circle at normal driving speeds...
https://www.youtube.com/watch?v=xTk_kPeA63c
https://www.youtube.com/watch?v=xTk_kPeA63c (turn the sound off, its just road noise) This is what happens when you go full bore into a big roundabout.
This kind of roundabout is used to join one large road to one or more small road (think two lanes going from 6-12 on the clock, with single lane road at 3 & 9)
In the UK, we don't normally have stop signs, as most junctions have clear rights of way (https://www.rac.co.uk/drive/advice/road-safety/uk-road-marki... see "Give way to traffic on major road") In suburban roads, roundabouts are often used instead of stop signs. It allows much freer flowing of traffic in both heavy and light traffic.
Just don't look up the magic roundabout, thats just fucking batshit, we only have one. The reason why they keep it is because there is literally nothing else interesting about the place.
Rude. ;0P
Actually there's another in Hemel.
Hemel, Swindon or England itself?
Do they? I guess it probably depends on the country. Here in Sweden I'm pretty sure you can drive in whatever lane you like (unless they're explicitly labeled). But normal lane-swithching rules apply ofc and, importantly, when you enter a roundabout you have to yield to traffic in all lanes of the roundabout, not just the outermost one.
That's how most of the multilane ones are are in my part of the US, and that's what makes them terrifying to me. It requires too much trust that the other drivers are going to do the right thing.
It also doesn't fully protect vehicles already inside the roundabout. My father got rear-ended once while inside a roundabout by a possibly distracted driver and the car was a near write-off.
The main advantage of roundabouts is traffic fluidity. When compared to intersections with stop signs or traffic lights, unless it is full you can often enter a roundabout without coming to a complete stop first.
This is the "truck apron". Virtually every roundabout in our town has one, and it's up a little curb to get onto it. A little too much for cars to sensible abuse, but a dirt motorbike gets over them easily. :) Also when it snows in people can't tell where the apron starts, so traffic tends to cut over it.
Cars going the wrong way is a non-issue. It is clearly signed how you're supposed to drive, and if they constructed it properly going the wrong way means you have to do a left turn of about 120 degrees. It feels so unnatural that you'll have trouble doing it on purpose, let alone accidentally.
Why? We are talking about people, who don't pay attention and drive through an intersection, the same people won't pay attention and won't slow down, let pedestrians to cross and do other silly things in the video.
> It is clearly signed how you're supposed to drive
I don't know where you live, but roundabouts near me have no signage of any kind. They are intersections with the center removed, on one near my home I've been seeing the same woman doing a left turn once a week (we seemed to have the same schedule so going there around the same time). Not to mention that many people don't pay attention to whatever signage you will put up, it's not a magic spell.
It's like turning right at a T junction. You simply can't do that at high speeds because you will flip your car. Most drivers have enough self-preservation to prefer slowing down over crashing their car.
And as for the self-preservation, running a red light on a normal intersection is doubly dangerous as you are risking both frontal and side collisions from both sides, if self-preservation is how roundabouts are safer then a normal intersection is doubly so (it is not, people who cause accidents are not guided by self-preservation).
Who is protected exactly?
https://c.tenor.com/GLRaFTDEqngAAAAd/roundabout-poland.gif
https://c.tenor.com/0YMymTe85q8AAAAd/roundabout-car.gif
Maybe not if you grow up with it. But there certainly is if you are a British tourist, used to always giving way to the right.
For anything above that where I have to cross lanes to get to the center circle and then cross lanes again to get back out and exit, I'd rather just have a conventional traffic light-controlled intersection. (I try to minimize lane changes when I drive.)
Same here, but by the end of a recent trip to Iceland, two lane roundabouts were easy-peasy. The learning curve is short in my experience.
They're perfect for crossings with low to middle traffic. No useless waiting time, good visiblity and no need for traffic lights.
For heavy traffic, though, they're useless as the car flow of one entry/exit can take over the roundabout and block all other entries.
Also, it seems hard to understand for many drivers that regulations regarding changing lanes don't change in a roundabout. So more than 3 lanes are not advisable in my opinion.
Not wrong, but traffic lights can be added to roundabouts as well ("signalized roundabouts")
* https://www.youtube.com/watch?v=XCrAPcUzOdw
So if an intersection is (e.g.) four-way, and one particular entrance monopolizes things than it can be given red at times and the others green (and than one-green/three-reds).
See (e.g.) "Performance and Safety of Roundabouts with Traffic Signals" by Tracz and Chodura:
> The paper presents designs, advantages and some drawbacks of various layouts of roundabouts with traffic signals, used in urban arterials on crossings with large traffic volumes. The authors analyze signal settings with alternative phasing used at intersections that can provide the intersection capacity of about 6500 veh/h in 2x2 lanes arterials or even 8000 veh/h in 2x3 lanes arterials. Accident statistics for roundabouts with traffic signals in Krakow are also given and discussed. In addition, presented are practical examples of changes of signalized roundabouts geometry; reconstruction into a form of turbo- roundabout and its effects regarding traffic safety and good performance.
* https://pdf.sciencedirectassets.com/277811/1-s2.0-S187704281...
And §8.1 Traffic Signals at Roundabouts:
* https://www.fhwa.dot.gov/publications/research/safety/00067/...
Also:
* m463 ↗ wow this stuff is like factorio, where you learn signals. crote ↗ You can! m463 ↗ wow.
too bad you can't go underground.
In The Netherlands there are several multi-level roundabouts, with one level for cars and another for bikes and pedestrians.
Somehow I'm reminded of those old pneumantic mail tubes interwoven with the fabric of the building...
Inside cites, those traffic lights in intersections were usually also semaphores for pedestrian crosswalks. So when you replace the intersection with a roundabout, you usually keep the traffic lights for the crosswalks alone. At the speed a car exits a roundabout, a non-regulated crosswalk could be quite dangerous.
When visiting for the first time on a specific spiral roundabout:
1. Lane markings are faded
2. You do not know the specific lane unless you come very close to it and have to make a quick decision
3. Often due to queued traffic you cannot even see the lane marking until its too late.
Because of this I have seen people change lanes on a roundabout because they made a mistake and its dangerous.
[1] https://www.google.com/maps/place/Sainsbury's/@51.5080462,-0...
* https://www.youtube.com/watch?v=e6TsX9Ob91w
I'm more curious about the straight-through path of [1] above.
This is the round-about layout [2]
None of the above tell the precise lane to take. Only when you enter the roundabout you will know. See.[3]. Imagine cars waiting on these markings. This is what frustrates me the most.
[1] https://www.google.com/maps/@51.5066257,-0.5789164,3a,75y,32...
[2] https://www.google.com/maps/@51.506316,-0.5784722,3a,37.5y,2...
[3] https://www.google.com/maps/@51.5076664,-0.5804344,3a,75y,29...
1. They switched from 3 lane traditional to 2 lane spiral roundabouts. There are signs well before you enter the roundabout telling you what lane you need to be in, so you can get into the right lane early. We have a lot of snow in winter, so road markings are not visible.
Example of a sign indicating which lane you need to be in. After this sign, there are two more signs indicating lanes before you get to the roundabout - the next has destination names.
https://maps.app.goo.gl/zJLaFC78i232mUkh6
2. The lanes on the roundabouts have solid white lines which you must not cross. You can only cross lanes to go more towards the center. I'm surprised, but people actually follow this rule.
Example of lanes (and a rare sight of police...)
https://maps.app.goo.gl/HbnkXYkacX3dfq4j6
3. They added speed bumps on the roundabout. This slows down the traffic on the roundabout, giving more chance for vehicles to enter.
https://maps.app.goo.gl/fMKBjocYAFTmpE6ZA
Also, on the small side where you have traffic circles rather than roundabouts, those also suck.
There are "traffic circles" that aren't roundabouts but just a round block in the middle of an intersection that requires the traffic to move around in a circle so cross traffic is slowed. Also called a "traffic calming circle."
https://www.seattle.gov/transportation/projects-and-programs...
That could also be a location specific term too. These circles are very common in Seattle.
Look up on wikiprdia, there are even different types of roundabouts
[0] King Charles is so uncharismatic I do not acknowledge his existence
[0] https://en.wikipedia.org/wiki/Michigan_left
Interesting. Can you elaborate? We have a few of them (and growing) by me and they’re fantastic as far as I can tell. No stopping every block for stop signs, I’ve seen landscaping truck with trailers sneak through them fine, and it’s so much easier on a bike or while walking. What’s the downside?
People generally don't slow down for lights, and lots of times accelerate to make it through before it turns red.
A three lane roundabout may be annoying when encounter as a tourist but the majority of locals going about their daily commutes quickly master them. For a three lane roundabout the inner lane is left turn only. The inner lane is left turn or straight and the right lane is right turns only.
The ones in my area have ample signage indicating which lane allows for each type of turn.
I’m much more skeptical about how roundabout users fare when they are people walking or riding bicycles. At least in my city, we've had roundabouts for years, and the yield rate for pedestrians is ghastly— like, sub-50% of drivers stopping for someone waiting to cross and remaining fully stopped until the person is completely off the roadway. In theory this is a fine of hundreds of dollars ("failure to yield to crosswalk"), but it appears to receive basically zero enforcement in practice.
As a result, the fancy multi use paths that accompanied our roundabout installations get little use, since it's obvious to anyone who tries them how dangerous and unprotected they are.
Roundabouts feel safer than a 4 way intersecting when I'm in a car even if it's annoying to have to slow down and accelerate again when there is very little or no traffic, which is normal in the countryside. It also consumes more fuel, wears the car, adds to pollution.
It's different when I'm riding my bicycle. Roundabouts put me closer to cars, especially if there are traffic dividers that force cars closer to the side of the road. Then cars are usually slower than a bicycle in a small or medium sized roundabout (think of race bicycles with drop bars,) which adds up to chances of being packed between two cars. My feeling is that what's good for cars is bad for bicycles.
As a cyclist I can see what's around me much better than when I'm in my car. Intersections don't feel like a problem because of the extra visibility. When I'm riding I long for old times straight roads, with a line on the side and half a meter of asphalt on the other side to ride on. No roundabouts, no speed bumps especially the 3M style plastic ones, which I can jump but they are annoying. All those safety devices, including roundabouts, increase fatigue and danger. They are also the main reason for crashes in bicycle races but that's not an issue for normal people.
Finally, as I both drive and ride I know how to behave not to put in danger the cyclist. When I drive I don't overtake bicycles before a roundabout because they'll be at least as fast as me. I don't overtake when there is a short traffic divider which narrows the road. A long one, oh well, I have to. Same thing when I approach an intersection where I have to yield or stop. Bicycles will be definitely faster there because they can look around better than me and decide what to do quickly.
When I ride and I'm approaching a roundabout or entering a short narrowing of the road I look behind me and if it's safe I lean a little to the center of the road to prevent cars to overtake when they'll be forced to come close to me.
"Researchers in Belgium found that single lane roundabouts without a protected bike lane increased crashes by 93%, while Danish researchers said roundabouts that did have separated lanes saw an 84% reduction in crashes."
CNBC: Roundabouts Are Safer. So Why Does The U.S. Have So Few Of Them? https://www.youtube.com/watch?v=atORPw-w83I
"All those safety devices, including roundabouts, increase fatigue and danger."
They literally distract from the traffic when you aren't in a little isolated house on wheels where people are prone to forget that traffic even exists. All those things designed to help getting a driver's eyes off WhatsApp require cyclists to get their eyes away from traffic.
On the topic of roundabouts, one thing I rarely see discussed (never?) is that traffic lights conveniently compress the vehicle stream into packets of high and low intensity, greatly helping smaller intersections downstream. Roundabouts on the other hand flatten the vehicle frequency and of there's a difficult place to enter or cross the stream, even a modest amount of traffic can be too much. In the end everything that isn't a roundabout can only be navigated by relying on someone in the dominant stream showing off compassion with those waiting. This makes everything go even slower and you quickly end up with even dominant streams going less than walking speeds.
I have a hypothesis that roundabout-dominated road graphs are particularly prone to effective throughput dropping once a certain threshold of throughput demand is reached. Traffic light dominated graphs are immune to this if drivers are just a little careful to not enter an intersection before they can assume that they will be able to leave before the lights change.
You might have a curve leading up to the round about plus roundabout signs, plus give way signs, plus 300, 200, 100 yard markers, plus painted lines on the road that get closer together as you approach, and finally the <<<<< sign on the roundabout itself.
At least where I live, there are two rules for traffic circles: (1) yield to traffic that is already in the traffic circle, and (2) when two cars arrive at the same time, yield to traffic on your right.
Rule 1 is the same as for a roundabout, but rule (2) is a bit strange when the two are put together. It creates a scenario where if the leftmost car doesn't yield for whatever reason (perhaps they thought they arrived a microsecond earlier), then now they move forward and become "traffic in the traffic circle", which means they steal priority and the right-most car now has to yield to them. If the rule were flipped the other way, such that we default to always yielding to the car on the left, then this wouldn't happen; it would work just like a roundabout, and the order of yielding priority would be the same regardless of agreement on the exact timing of when each car arrived at the traffic circle.
So, why is it that at a traffic circle we yield to traffic on the right, rather than the left? Is it just to be consistent with 4-way stops?
Yeah, that seems mad.
Personally I find it confusing that yielding works the opposite way on roundabouts and 4-way stops, and nobody else in my neighborhood seems to know what to do either. Whether people yield to me seems to depend mostly on the size of the vehicle I am driving.
There are a few non-standard roundabouts that has no yield sign and the lane goes straight into the roundabout but then it usually doesn't have an outer lane before that entrance.
Roundabouts are fine if the rule is, "Just get in there without hitting anybody and go around until you're ready to leave," but expecting anything more than that from most drivers is a lost cause.
We have tons of 2-lane ones and everyone understands them…
e.g. for a standard two lane roundabout with four exits, if you enter in the left lane, you can exit directly out of the 2nd, 3rd, and 4th (i.e u-turn) exits, but always in the left lane of the exit. If you enter in the right lane, you can exit out of the 1st or 2nd exits, but always in the right lane of the exits. With this design cars travelling alongside you can never cross your path, only cars entering the roundabout ahead of you can cross your path and it's their responsibility to yield.
The thing that most often causes problems is people in the outer lane NOT exiting (e.g. thinking they can take the third exit from the right lane) and swiping the car in the inner lane correctly taking the second exit.
In practice, people are not able to navigate two-lane roundabouts in a compliant and safe manner. Any intersection of roads busy enough to have two lanes in each direction is too busy for a roundabout to be safe.
I think drivers will get used to them and in practice there will be few collisions.
I think drivers will avoid them at all costs since even low speed collisions can cause extremely expensive repairs (and even total an older vehicle) meaning they'll never get the practice they need to navigate them safely, yet eventually those drivers will find themselves in a situation where a roundabout can't be avoided and suddenly it's chaos for every car in the intersection.
Even if multi-lane roundabouts were suddenly everywhere we'd probably need generations of new drivers trained to use them in drivers ed classes as teens before you could just trust people to be able to navigate them correctly
Yes, in that case a driver not understanding the rules of the road (that you can't take the first exit from the inner lane, which is usually clearly signed) could cause an accident. The exact same way turning right from the left lane in a signalized intersection can cause an accident. The question is, what's the damage of an ignorant driver and how fast do people learn? The research indicates that right-of-way incursions in a roundabout result in dramatically fewer injuries than right-of-way incursions at other types of intersections, and the research also indicates that contrary to your belief, drivers actually do learn how to use them.
The exception is you can obviously not shoot straight from the left lane to the first exit.
In a 2 lane roundabout it is very simple. Enter in the left lane and you can exit 2nd or 3d, enter in the right lane and you can exit 1st or 2nd.
Where it gets complicated is roundabouts with 2 lane entry but only 1 lane in the third exit. Then you have to change lane right halfway through and be careful with people entering prematurely from your 1st exit, or people incorrectly staying in the right lane past the 2nd exit. It’s not always obvious but for those entering the rule is the same, since they enter after you, they should yield to you.
This however does not stop accidents to happen all the time in this situation because of drivers trying to get past the traffic jam by going inner lane in high speed and then exit in front of traffic trying to get to next exit. And mostly without blinking at all.
The US is unfortunately loth to install any sort of divider more than paint or a feeble plastic post, and less than a jersey barrier.
Example: https://maps.app.goo.gl/3z6NZXGdb2HRVtfW7
The 90->270 car sees the right indicator and lets the other car passed.
The real answer is somewhere between the above and the 90->270 car waiting to enter the roundabout because it is not sure if the other car is actually going 0->180 or 0->270 because they are a shit diver that doesn't indicate on roundabouts.
This is not true with most roundabouts in North America at least. If you look at the diagram GP posted, you do not change to the outer lane to exit. You exit directly from the inner lane. In fact, you NEVER change lanes in a roundabout. The reason this works (where the inside lane crosses the outside) is because the roundabout is small enough that the traffic in the outside lane has to let you exit as part of yielding to enter the roundabout in the first place. After that, as long as everyone respects which exits they're allowed to take from which lane, there is no more crossing traffic. In practice, if you are in an inside lane, you want to keep an eye on the outer lanes to make sure someone isn't trying to take a later exit than they are allowed.
From GP link:
> Do not change lanes in a roundabout
> Do not travel in the outside lane further than allowed as it may create a hazard for the vehicle exiting the roundabout from the inside lane
When you exit from the inner lane you necessarily have to change lanes because the inner lane is completely inside the outer lane. You may not think of it as a lane change because you're going across the lane not merging into it, but it is a lane change and you have to pay attention.
No, they have to yield to YOU because you're already in the roundabout. It's hard to believe, but trust me, this is just how it works and all of the links I've posted agree. The reason why it works is because when you're in the situation you describe, for the person entering at the second exit to be a factor, they would have to be entering as you're already alongside the second exit and in the process of exiting at the third. So they need to be yielding to you as they will be crossing your lane. Part of waiting for the gap is waiting for the exiting traffic to clear. Not for only YOUR lane to be empty.
Here's a video from Minnesota timestamped to them talking about exactly this scenario in detail. Namely, yielding to all lanes of cross traffic: https://youtu.be/CEhNboz5GPk?si=LxdVQZx0MHrYhl8w&t=196
> With multi-lane roundabouts, it is important to stop for vehicles in all lanes of traffic. Wait until there is a gap in all lanes of traffic and then enter slowly. Never try to enter alongside cross traffic or assume any driver's intended path. One of of the most common mistakes people make when entering a roundabout is failing to yield to all lanes of traffic. Yield doesn't mean just slow down or merge. Yield means that you must wait until all traffic in the roundabout has cleared before proceeding. Make sure that no one is in either lane of the roundabout and then proceed.
The video also has a good overhead view that is better than most at showing the scale of the roundabout. The important thing to note here is that to enter the roundabout, you have to cross the lanes that are exiting, not merge into them. So you are yielding to all exiting lanes.
The person following the outside route from 90 must yield before even entering. It's very confusing until you're actually in them, but they're small enough that what you're saying usually isn't really a problem (at least in well designed roundabouts). When the car at 90 enters the roundabout intending to take the 270 exit, they yield to traffic in ALL lanes that might be exiting. Not just traffic in the outer lane. If they were intending to take the 180 exit, they only need to worry about traffic in the outer lane (or people incorrectly changing lanes when exiting).
The shitty part about roundabouts is when people allow blocking of the view to the right on the round about so you are unable to see incoming traffic till its almost on the round about.
Newbie drivers I talk to/drive with are much more worried/unsure about crossings (both the ones without traffic lights and the big ones with many lanes) and of course about parking.
Of course, there will be SOME people who are clueless on roundabouts, similar to how there are always some people who will stop on a highway after missing an exit and pull back. But let's not argue about the long tails.
IMO if you learn to drive at a time when roundabouts are already ubiquitous, they are trivial. At least I found other aspects of driving more difficult.
What?? People do that??
My mind is blown. I've never once seen that happen, so the possibility never entered my mind. Now that I think about it, though, I should probably be more surprised that I haven't encountered it.
https://youtu.be/r86kxxU-LUY
One that gets me every time I go past is one where there's like 20 signs saying that both lanes continue to the main road to the right (270 degrees around, the UK so driving on the left), but I don't think I've ever been through there and not have someone try to merge in to me trying to get into the left lane to exit, despite both lanes leading to that exit.
Of course the de facto standard here (which many people actually think is the law) would be "give way to the right" (i.e. left for US) meaning some people will proceed without stopping even if the car to their direct left got there just before them. I think this is predictable since more risk falls on the driver who is going to get T-boned in their driver side door if they don't stop so they will be naturally cautious.
I can't speak to the area you live, but where I'm from we get along just fine. Yes sometimes you still get the odd unfamiliar driver that doesn't understand them, but for locals there's a critical mass where roundabouts stop being avoidable and you adjust.
See also: https://www.iihs.org/news/detail/safety-at-two-lane-roundabo...
And that means everyone has to watch both left and right at the same time while also trying to figure out layout (Will the outer lane force me out when I do not what to? Some roundabouts are like that. Will the inner lane keep me trapped? etc)
It doesn't help that often those signs are pretty confusing all by themselves (at least the ones I've seen), and can't really be grokked from a brief glance driving by.
It would be better if all such roundabouts were consistent in how you should navigate them, but that isn't the case in my area.
Source? Not doubting you, just want something to reference in the future.
There seems to be quite a bit of literature that flatly disagrees with this statement. Perhaps you could add a source? The conventional wisdom where I'm from is that multilane roundabouts don't reduce the absolute number of crashes (and might even increase crash rates), but they still dramatically reduce the severity of crashes.
Canada:
> However recent data in the United States and Canada are showing that collision frequency at multi-lane roundabouts is often higher than expected, and sometimes higher than the prior signalized intersection. This trend is worrisome given that roundabouts are often constructed as a means of increasing safety. The good news is that fatal and injury crashes are almost always reduced with roundabouts, even if property-damage-only crashes are not.
https://www.tac-atc.ca/sites/default/files/conf_papers/weber...
Netherlands:
> Multi-lane roundabouts. These are less safe than single-lane roundabouts, but still safer than other types of intersection [22]. Multi-lane roundabouts are less safe because they have a larger number of conflict points, they are more complex, driving speed is higher, and they have a less sharp entry angle [23].
https://swov.nl/en/fact/roundabouts-how-safe-are-different-k...
US:
> Roundabouts force drivers to slow down and all but eliminate the most severe types of intersection crashes — right-angle, left-turn and head-on collisions. Single-lane roundabouts see fewer total crashes of any type.
https://www.iihs.org/news/detail/safety-at-two-lane-roundabo...
Two-lane roundabouts are larger; cars go around them faster. There is ambiguity. Some cars short-cut using the middle lane, and veer right out of it to their desired exit. Cars in the outer lane might be wrongly assumed to be turning off at the next exit. North American drivers get really confused by two-lane roundabouts.
I don't think these situations will typically lead to anything worse than fender benders.
The same intersection without a roundabout could be host to fatal collisions, when two vehicles enter at speed and hit each other in the middle.
Not at all. A large enough roundabout with good visibility from the approach can allow you to traverse it without slowing down at all - if the speed limits coming up to the yield line are appropriate, and traffic is flowing.
There's a sense in which a roundabout is just a short circular section of highway with a series of on and off-ramps around the edge. Well designed onramps allow you to merge without slowing, and off-ramps let you leave without disrupting traffic. Roundabouts can permit the same.
Since even a fender bender can cost many thousands of dollars in repairs that's still pretty terrible. Speed bumps slow drivers down too and don't risk people turning into you because they were trying to exit from the inside lane of a roundabout.
The two lanes are there in larger, busier roundabouts to reduce collisions, not for "slower traffic, keep right"; it's not a freeway. Cars enter the outer lane, and may use the inside lane to avoid other cars entering.
The problem is road users new to the road do not know which lane to be in already and they are pressured to go fast. The instant it looks like they've chosen a lane, a driver from behind who is familiar with the layout closes the gap in the other lane, trapping them.
This can be mitigated a bit by the first user having the confidence to slow down and straddle lanes until they are sure of the correct lane, but it's surprising how quickly such opportunities are missed.
The real problem is familiarity with lane layouts allows the road to operate at far higher capacity then normally possible and with less maintenance. They are squeezed to their limits in morning rush hours comprised of mostly familiar users. You'll even see users observing essentially invisible road markings because they're doing it from memory. No chance of you're unfamiliar with the road. Roads start to fail way before 100% capacity, but these lane markings allow that to be squeezed further during rush hours.
If you are in a wrong lane, the safest thing is to continue on it, exit the roundabout and comeback again or go around the roundabout.
Of course you could just not change lane, to the wrong way and safely correct your course later. This is preferable but people tend to get stressed out in those situations which is also bad for safety. Not to mention that a safe but ineffective road hasn't really achieved much.
I won't bother trying to expand on my comment to you, you're clearly not someone I'll be able to communicate comfortably with.
https://www.google.com/maps/@51.7874467,-1.278506,17.57z?ent...
Coming out of Oxford on the A4144 there are two lanes; the left lane is for taking the first two turns and the right lane for the remaining three. But, drivers unfamiliar with the layout who haven't seen the markings, or who fancy jumping the queue, will sometimes use the left hand lane to go straight ahead onto the A44. There's a similar situation coming from the A40 to the East.
I've seen a few accidents there and even been involved in one as a result of this (someone tried to undertake me at speed as I exited, and caused a collision, 100% their fault according to our insurers).
> drivers unfamiliar with the layout People familiar with the layout drive even when the markings are completely faded. It causes lot of anxiety if you are not familiar. It happened to me once where I was in a wrong lane. I continued on it as it was the most safest thing to do but the next exit was onto a motorway :). I was so angry with myself.
But of course not everyone notices every sign (and some drivers just wilfully disobey them if they think it'll save a few seconds...)
[1] https://www.google.com/maps/@51.787062,-1.2794264,3a,15y,317...
Based on the lines used in the 2-lane roundabout in the video in question, all right lane entrances should be forced to take the first exit.
Properly signed roundabouts make this clear. Here's an example: https://www.google.com/maps/@44.1104851,-121.2794584,97m/dat...
Simple roundabouts are fine.
Fortunately, I live in one of the few US cities that really are bike-friendly, so 90% of the time I'm on a bike path that is physically separated from where cars go.
The right lane is only permitted to turn right or continue straight. So the pink car is not supposed to continue counter-clockwise.
The left lane is only permitted to go straight or turn left. Thus it won't run into the cars on the right lane.
A collision could occur if people don't follow the rules, much like everything else when it comes to driving a car.
It's also worth noting: this are notably more difficult to traverse during fresh snows. While starting and stopping is certainly an issue in snowy intersections, a roundabout introduces a lot of turning, and especially so in cases of spiral ones. Two-lane roundabouts basically have to become one lane during a heavy snow, there just isn't enough grip to safely maneuver one with multiple lanes. And that's with Wisconsin lanes, which are notably large among US states.
Here in Michigan there are roundabouts everywhere. And I'd estimate oh maybe 20% of the drivers know how to use them. Because of that, I absolutely hate them.
A roundabout around here is just a total luck of the draw on what you will get: people treating it like a four way stop, people ignoring it completely and just blasting straight through at top speed, people going into the roundabout then stopping at every merge point, people going into the roundabout and stopping to let someone else merge in front of them, on and on. I'm still amazed at what people do.
I suspect the people who blast through it at top speed and cause an accident cause other people to turn into the type that treat roundabouts with extreme caution.
Just outside my neighborhood I must have seen 10 accidents in the past two years alone. That's a lot of accidents at an otherwise low traffic intersection.
Every time a roundabout is proposed near me there’s a vocal group of opposers. I just don’t really get it since in many cases a roundabout is preferred to an intersection in my opinion. But one comment I read summarizes it I guess:
“Drivers here are just too dumb for a roundabout. We can trust them to think.”
And I guess I sort of agreed. Driving in America is weird because so many people do things like passing on the right, not using turn signals, and driving the wrong speed in whatever lane they’re in causing chaos.
Mini Motorways also had them from the get-go, and they're much more robust than simple 3/4/5/6-way intersections.
Example: https://www.reddit.com/r/bayarea/comments/10pihgk/roundabout...
https://maps.app.goo.gl/BVrKXUqV6Ck7QTdQ6?g_st=ic
The problem is that it's not really a circle. It's like half-circle/half four-way stop.
A new roundabout in Brevard, NC has a very tight turning radius. There is a sign warning drivers in the outer lane to watch out for tractor trailers who will have to take both lanes to navigate the circle.
One went in here where people normally drive 60 mph:
https://maps.app.goo.gl/Ugnm36mkeHs2zpu7A
On Clark straight through, I would look for approaching traffic from either side or ahead and would cut across the hatched area, mostly maintaining speed. It's honestly better than stop signs or stop lights.
The second one is a bit of a mess. The fact that it is physically possible to take them at 60mph means they screwed up the design. They should've used something like slightly raised cobblestone for the hatched area, and they should've used a raised shoulder at the entrance/exit. This roundabout looks like it was designed by someone who has only ever seen it in a textbook, and never actually driven on one.
PS: One place that doesn't do proper traffic design (or architecture): Texas. They insist on placing massive concrete dividers everywhere and have camouflaged by wear obstacles in the middle of paths that are injurious to bicyclists. It's nothing like the Netherlands where there aren't many random, dangerous surprises.
The alternative (at least from my experience in the US) is a 4-way stop, and is worse for all those criteria.
[1] https://www.apsed.in/post/conflict-points-at-intersection
I live in the Netherlands, where roundabouts are very common. In many cases, they are an improvement.
But NL is also a huge bike country. And at most roundabouts, bikes have right of way. So as a car driver, you have to worry about other cars as well as bikes which may turn (go away from the roundabout) or continue (cross the adjacent road circularly around the roundabout.
In good visibility conditions, it's ok. And by OK, I mean it can still really f* up car traffic, especially when it is a high traffic area not far from a school. In lower vis conditions, and/or when electric higher speed bikes are concerned, it becomes a whole new kind of danger.
I would argue that the benefits of roundabouts diminish or fully disappear when the number of lanes exceeds 2, or when traffic lights are added to roundabouts, or (and!) especially when bike paths intersect with and circulate around the roundabouts.
The fact that it's on a case-by-case basis an not actually a consistent traffic law is really awful. To add insult to injury, the only signage is usually a yield sign painted on the road that is invisible as soon as it's dark and the road is wet. And this is of course further combined with the absolute scandalous amount of cyclists who don't have lights at night and are dressed in fully dark clothes.
Roundabouts are already a traffic situation that require heightened attention as a driver, so in the interest of safety I believe crossing cyclists should yield to cars at the exit. It's too many things to worry about otherwise. But at the very least, make it the same everywhere so it's always absolutely clear to both drivers and cyclists who has the priority.
Doesn't the red asphalt denoting a cycleway also typically continue across the exits when cyclists have priority?
The confusion can arise inside built-up areas where there's a separate bicycle path, usually close to the car lanes.
I hate these so much. Seems to break the purpose of a roundabout in the first place - to let a single entry and exit pattern dictate the traffic.
Stoplights in them fundamentally break their benefit, which is smooth, one-way flow.