[bnralt]

Online I see this mentality that roundabouts are great no matter what and it seems really strange to me. It really depends on the design of the roundabout and the traffic conditions. Where I grew up there are a lot of roundabouts, but many of them are so dangerously designed I started actively avoiding them. It’s not that you can’t poorly design a four way stop, but it seems to be much less common, for whatever reason.

I see people complain about roundabouts with traffics lights and how it negates some of the reasons for the roundabout. The thing is, these aren’t just put in for fun, usually they’re in areas with extremely heavy traffic where merging can get extremely difficult which leads to long backups (or in cities, accidents that can shut down traffic).

Roundabouts can be great when used well, but they’re hardly the silver bullet that online discourse often portrays them as.

[lmm]

They absolutely are. Even if they don't prevent all collisions, they turn T-bones into glancing hits and so save a lot of lives. The worst roundabout beats the best 4-way stop any day of the week. Sometimes there really are easy answers.

[bnralt]

> The worst roundabout beats the best 4-way stop any day of the week. Sometimes there really are easy answers.

Maybe you haven't seen the worst ones, then. For instance, one by my house had traffic lines which gave people the wrong impression about the right of way within the roundabout, leading to every vehicle treating driving like that. I actually drove like that as well for a long time - when you're spending every day driving the exact same way that the hundreds of other cars surrounding you are driving, and the lines on the road suggest that it's correct way to drive, it's easy to mistakenly think this is what you're supposed to be doing.

Then it hit me one day - this isn't how right of way works in a roundabout at all. I talked to others in the area, who were surprised when I brought it up. That's what the lines implied, that's what everyone _did_, but that's not how it was supposed to be used. Everyone was driving through this incorrectly. And it was a major roundabout, that had some of the heaviest traffic in the city.

Maybe it didn't matter because everyone was driving incorrectly, which worked most (but not all) of the time? But when it wouldn't, the accident would be a T-bone, so we can't say that roundabouts eliminate those.

Years later someone in the city seemed to realize it, and changed the design of the roundabout. It's better now, but there are still a few areas they overlooked that have the potential to cause accidents.

[Arn_Thor]

I'd really like to know where this was or see some pictures of it. It's almost inconcievable that something designed like a roundabout would be more dangerous. It might indeed cause more accidents due to the kind of confusion you describe, but at the very least the angles and grading should lower speeds dramatically and result in fewer deadly accidents.

[bnralt]

It's set up like this - busy avenue with lanes (left to right) 1, 2, and 3 enter into roundabout with circles (inner to outer) A, B, and C. The problem is that half way around the circle, where the avenue continues, A, B, and C then have lines indicating that you can either continue on the circle or move in a perpendicular direction to the circle and exit back such like this A -> 1, B -> 2, and C -> 3. And that's what everyone does. The problem is If someone from C is going around the circle, they're going to t-bone anyone going A -> 1 or B -> 2, and there's no moment to prepare because A or B is going to be suddenly cutting in front of them.

Or to visualize it another way - if you can image those intersections where there are two right turn only lanes, and one lane to the left of them that's right turn or go straight. Now imagine if all three lanes were right turn or go straight, and everyone made right turns - but if someone in the far right lane is going straight, they're plowing into the cars turning in the other two lanes.

After years they eventually fixed it and made the two outer circle lanes right turn only, which is what they should have done at the beginning. But even there they screwed up, because there's a street that enters the circle right after the right turn only signs, so if someone is entering from that direction and isn't familiar with the circle it's possible for them to ram into the other cars.

[USiBqidmOOkAqRb]

PIT maneuver is not a T-bone. Even if you cut across a lane (from C to A) there won't be enough of lateral velocity to make it potentially deadly. That's one the of the major points of roundabouts.

[Clent]

I live in an area with many A, B, C as you call them. Assuming we're going backwards, where A is right most lane, with these three lane roundabouts it's always A can only turn right, C an only turn left, B is for going straight, but can also turn right or left.

There are variations on this, sometimes, B can only go straight so that C can also go straight. C can also be used for a fully controlled U-turn. In fact, C is has the markings such that one can just go around and around and around forever in if one chose to do so.

All of the roundabouts here have overhead signage leading up to them that indicates which lanes are for each direction of travel. There are also lines on the roads themselves have solid and dashed lines. Never cross solid lines, optionally cross dashes. We get snow so lines aren't always visible.

I've been through many different roundabouts countless times and there is occasionally someone that doesn't get it right but the traffic is moving slowly enough that it unusually only leads to honking.

One strategy is to watch the faces of other drivers, people will be looking in the direction they will be turning.

[Aeolun]

Just because you drove wrong does not make the roundabout bad. That would require you to compare accident numbers from before and after. I’m fairly certain the stats lean in favor of even terribly designed roundabouts.

[bnralt]

> Just because you drove wrong does not make the roundabout bad.

You seem to have misread my post. Everyone drove wrong. I seemed to be the only one to notice it, and started avoiding that roundabout, because driving with the correct right of way rules during busy times would lead you to t-boning another car. Other people I talked to said "no, that's just how you're supposed to drive on that roundabout" (it wasn't, and the signage was eventually updated many years later).

If _everyone_ is driving through it incorrectly doesn't make it a bad roundabout, than I suppose no roundabout can be bad. If it's always the fault of the drivers and never the design, you can't really say 4 way stops are any worse in this regard either.

[Aeolun]

I think you missed my point due to me saying something about driving through the roundabout incorrectly. My apologies, that was entirely besides the point.

I’m trying to say that everyone driving through it incorrectly is not a great metric to judge bad roundabout. If everyone does it wrong and it’s still safer than a regular intersection, then is a success.

Of course I don’t know the numbers involved, so I can’t say if that’s the case here.

[shiroiushi]

>Even if they don't prevent all collisions, they turn T-bones into glancing hits

No, they don't, at least not in America. When you let American traffic engineers design a roundabout, you get this: https://www.google.com/maps/@38.8643875,-77.2755474,583m/

[esskay]

Nobody in their right mind would ever class that as a roundabout. You dont stick a high speed road directly through a roundabout.

An actual roundabout DOES solve the tbone issue.

[lozenge]

That's... Not a roundabout. It would be funny if it weren't so scary.

[ColinWright]

As others have said ... that's not a roundabout.

Here's one of my favourite hybrid "roundabout" junctions:

https://www.openstreetmap.org/search?query=Boughton%20Heath%...

[shiroiushi]

>As others have said ... that's not a roundabout.

American traffic engineers would apparently disagree with you.

[ndsipa_pomu]

That looks like a Hamburger Junction (or roundabout interchange https://www.roads.org.uk/interchanges/roundabout-interchange).

I think they're a bad design as they encourage drivers to go fast with the sweeping corners etc. Ideally, a roundabout should be designed to slow traffic joining it to reduce collisions and their severity. Trying to keep vehicles moving quickly at junctions is just asking for trouble.

[USiBqidmOOkAqRb]

It's disheartening to see that much parking place around that spot.

[offices]

This reminds me of this oddity in Nottingham:

https://osm.org/go/eu8S4TeKc?way=50459468

(right-hand drive)

[123pie123]

similar one here, but with added lights https://www.openstreetmap.org/#map=18/53.479432/-2.281970

[shiroiushi]

The one I linked to in Fairfax County VA also has lights, though it might not be obvious from the aerial view. It's really a disaster of traffic engineering. It's probably the most complicated intersection I've ever driven through.

[davidgay]

You can actually screw them up: by our house (in California) they replaced a 4-way stop with a roundabout with no signaling on 2 of the ways, and a stop on the other 2. An absolute disaster, as the 2 ways without the stop assumed they had the right of way over people already in the roundabout.

After the neighbourhood complained, it's now a roundabout with 4 stops (not ideal, but not dangerous either).

[talideon]

The right solution would've been to remove all the stops. They defeat almost the whole purpose of the roundabout.

[Ekaros]

I thought the standard for roundabouts is yield sings on all entrances. Not stops, just simple yields...

[rjmunro]

This. If it's not the case that all entrances have a Yeild (what we call "Give Way" in the UK), it's not a normal roundabout.

The feature that seemed to be missing from the roundabout in the original post was any kind of signage. Normally in the UK, roundabouts have a sort of map view as you approach them, then on the islands are signs telling you where to exit.

[Filligree]

Yields, yes.

[bfirsh]

I can confirm these are dangerous. There are several of these in Berkeley and I got knocked off my bicycle on one of them for exactly the reason you describe.

I am from the UK and it makes me wonder why road design in the US is so bad. Just one minute of thinking about this as a lay person would reveal the problem with the design.

Is there some structural reason in the US that would cause it? Perhaps some lack of standards or approval process? Perhaps iteration speed is slower so they don’t get better? Some other incentives going on?

[pclmulqdq]

My personal hypothesis on this is that the worst 5% of Americans is likely both dumber and more sociopathic than Europeans, and the behavior of the worst drivers is what creates a lot of traffic and road accidents. If that is the case, you will not have the same kind of design that works in a high-trust, more cohesive society.

[Aeolun]

What should I imagine when you say roundabout with 4 stops? Isn’t that just an intersection that looks like a roundabout without functioning like one (entirely negating the point)?

[lozenge]

I guess drivers just don't realise they need to slow down or give way to anybody unless there's a stop sign, traffic light or they're turning into a different road.

[esskay]

Surely drivers know what Yield means though right? I guess the US might need yield signs at a roundabout given not all drivers will get the basics of how they work. There should never be a stop sign on a roundabout, the whole point is you're supposed to be able to keep going without stopping at all if theres nobody coming round it.

[turboponyy]

This is literally just a skill issue

[WillPostForFood]

No easy answers, no solutions only trade-offs. Perhaps better for safety, but they makes crossing as a pedestrian longer and harder. And while intersections designed for roundabouts can be pretty smooth, retrofitting undersized roundabouts into intersections designed a 4-way makes for ugly and difficult to navigate messes.

I like them, but it is a mistake to blindly install them anywhere possible.

[ndsipa_pomu]

What's wrong with mini-roundabouts? We've got lots of them here in the UK, mainly in residential areas and I don't see the issue with replacing a 4-way stop intersection (U.S. style) with a mini-roundabout. All that's needed is to remove the STOP signs and splash a bit of white paint onto the road to mark the mini-roundabout. Optionally, build up the mini-roundabout to make it harder to drive over.

[rjmunro]

In most of the world, unless the intersection has pedestrian features (like traffic lights with green men or islands with pedestrian waiting areas), it's better to cross the road away from the intersections. Then you only have 2 directions of traffic to worry about. AFAICT, in the US, crossing away from the intersections is illegal in many cases.

When Cycling and approaching a roundabout move to the middle of the lane and follow the same routes as a car. Yes you slow the cars a bit but they are supposed to be going slowly anyway. If you don't want to do that, you can get off your bike and cross as a pedestrian would.

[cameronh90]

Roundabouts not good for pedestrians and cyclists. In London we’ve been replacing roundabouts with other types of junction to improve pedestrian and cyclist safety.

We don’t have four way stops though so instead it’ll be min/maj junction or traffic lights.

[robjwells]

This is only true of typical UK-style roundabouts which are designed for motor vehicle throughput.

It’s extremely common in the Netherlands to replace crossroads and T-junctions with roundabouts to improve safety, but Dutch urban roundabouts are designed with safety as the main priority. This is achieved through single lanes, sharp entries, limiting forward visibility, and pedestrian and cyclist priority (via what are effective zebras).

For more information see eg: https://bicycledutch.wordpress.com/2015/10/13/explaining-the...

(Edit: fixed wrong link)

[cameronh90]

We should absolutely be deploying these where we can, but they do take up a lot of space relative to their traffic throughput, and are only really suitable for a fairly narrow range of traffic volumes.

NL seems to quite commonly have this kind of physically large but medium traffic suburban junction, but outside of Milton Keynes and the outskirts of some towns that got heavily developed in the 60s, it's hard to see many places where we could just drop it in.

[tinodb]

I don’t think they do!

> That the Dutch roundabout, including the cycle tracks all around it, can be built in almost the same space of a traditional junction is the reason why so many are being converted.

From: https://bicycledutch.wordpress.com/2014/02/23/junction-desig...

[ensignavenger]

In some cases, I see roundabouts used in places a stoplight would be much better. It isn't roundabouts vs 4-way stops, its roundabouts vs a whole bunch of other options.

[Auracle]

My experience driving in rural France was that nearly every intersection was a roundabout and it slowed things down dramatically. Many, many times I was the only driver within sight. Surely one of the two directions is more used and a couple of putting stop signs the other way would make more sense.

Roundabouts are great sometimes, but they aren’t a magic bullet.

That said we have a nasty intersection in the area on a highway that they’re going to redo, which absolutely no one could have foreseen 10 years ago when they first put it in.

The 3 options were j-turn or roundabout soon, or a full on overpass type system in another 10 years.

J-turns are awful, so while that was their first idea it was thankfully put down. It would have been even worse as it leads into a school and most buses in the area would have needed to do U-turns on the highway, as well as new teen drivers. In Minnesota.

Old people complained about roundabouts because even though they’re used quite a bit in the area apparently they don’t drive and don’t understand them.

So, 10+ million dollar overpass for a town of 2,000 it is, in 10 years. Let’s hope not too many more people die before then, eh?

[bluecalm]

That it slows things down significantly is a feature not a bug. Rural roads have a lot of accidents. In my country the most fatal ones. There are two main reasons for that: speeding and fail to yield. Often combination of the two. Roundabouts solve the issue as you have to slow down before the intersection.

[fransje26]

> My experience driving in rural France was that nearly every intersection was a roundabout and it slowed things down dramatically. [..] Surely one of the two directions is more used and a couple of putting stop signs the other way would make more sense.

Yes, that is by design. Slowing traffic down, also in relatively low-traffic areas, is one of the use-cases for roundabouts in France. Mostly around villages and/or industrial areas.

[DrBazza]

Try driving in England, rural or otherwise, and you'll see our current trend of adding traffic lights to roundabouts.

If you think roundabouts slow you down (they don't really), just wait until non-rush hour at one of these "roundabouts" when you're the only car waiting on several sets of red lights, or during rush hour when the lights have failed and it's totally gridlocked where traffic simply cannot pass.

[ndsipa_pomu]

To be fair, most of the gridlocked traffic is caused by drivers not understanding that they shouldn't enter a yellow box junction until their exit is clear and similarly, they shouldn't be nosing out onto a roundabout when their lane is already full - that's what tends to cause the issues.

[DrBazza]

True. It's in the Highway Code. Then again, so is 'move quickly past the vehicle you are overtaking, once you have started to overtake. Allow plenty of room. Move back to the left as soon as you can but do not cut in'. But you wouldn't know it driving on UK motorways.

[ndsipa_pomu]

There's a special ring of hell reserved for drivers that stay in the middle lane.

[makeitdouble]

You can mess roundabouts, but it requires a sever lack of competence that we rarely see TBH, and it can be progressively improved (signage, better visibility, lines etc)

I'm with you on how some will still be dangerous, and can require traffic stops. But it's still better than going back to a plain stops IMHO, and it's usually in portions where it was already dangerous before putting in the roundabout. In practice I've never seen a reversal of a roundabout to get back to a plain intersection.

[bnralt]

I don't think most of the ones here could be easily reversed, for what it's worth. The streets were designed with them in mind, so they're usually at the exact spot where 3-5 different roads intersect.

The number of bad roundabouts is pretty common here, though. But it wouldn't entirely surprise me (based on other things I've seen) if there was a level of local incompetence that went beyond the norm. You're right that they can be improved, but (I mentioned this in another reply), sometimes that takes years or decades for whatever reason (and even then, they don't fix all of the issues).

[onlyrealcuzzo]

The biggest problem with a 4-way stop in a busy city is that it can be easy to miss the stop sign which makes it easy to cause an accident, which could kill someone.

No matter how terribly designed, it's hard to entirely miss a roundabout. You basically need to be incoherent.

[closewith]

> It’s not that you can’t poorly design a four way stop, but it seems to be much less common, for whatever reason.

All four way stops are badly designed. Roundabouts are not always the best options, but they're always better than four ways stops.