Transportation engineer here: Multi-lane roundabouts don't typically have any safety benefits. Single lane roundabouts do.
Also, on the small side where you have traffic circles rather than roundabouts, those also suck.
Also, on the small side where you have traffic circles rather than roundabouts, those also suck.
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.
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.
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.
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.
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.
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.
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?
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
Source? Not doubting you, just want something to reference in the future.