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.
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.
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.
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.
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.
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.
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/
An actual roundabout DOES solve the tbone issue.
https://osm.org/go/eu8S4TeKc?way=50459468
(right-hand drive)
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.
Here's one of my favourite hybrid "roundabout" junctions:
https://www.openstreetmap.org/search?query=Boughton%20Heath%...
American traffic engineers would apparently disagree with you.
After the neighbourhood complained, it's now a roundabout with 4 stops (not ideal, but not dangerous either).
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.
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?
I like them, but it is a mistake to blindly install them anywhere possible.
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.
We don’t have four way stops though so instead it’ll be min/maj junction or traffic lights.
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)
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.
> 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...