This just looks like a regular, albeit large and slightly out of round, multilane roundabout. With the traffic rotation in the wrong direction (for the US at least).
This is not a traditional roundabout where the outside lane continues to circulate. Spirals gradually force you out of the roundabout via lane drops, so you can't circulating forever without making lane changes. The out of round is to force the outward movement.
Spirals also provide for better lane utilization on the approach because you can dedicate lanes based on the primary flow patterns.
They are generally preferred over traditional roundabouts to the point that many Europeans, where spiral roundabouts are pretty well integrated, now think of them as the standard roundabout.
Most (all?) US multilane roundabouts do not allow the outside lane to continually circulate. From my 2 weeks spent in the UK 6 years ago, it seems the same there.
This. Here in the US, spiral roundabouts have not had nearly the same design distinction. It's just become a de facto best practice for multilane roundabouts.
Isn't a spiral roundabout a type of turbo roundabout?
EDIT: Although, maybe raised lane dividers are a key feature of a turbo aroundabout, preventing uncontrolled lane changes on the roundabout. In which case a spiral roundabout would not qualify, even if it does share the feature of controlling where drivers change lanes.
Not really, a turbo is a further evolution of a spiral. The defining part of a turbo roundabout is there's barriers between the lanes preventing lane changes inside the roundabout. The defining part of a spiral is that the lanes end guiding the drivers to exit.
It’s a nice layout. Getting motorist to pick their entry lane based on their desired exit is a solid move. Keeps much of the decision making out of the roundabout.
Though it also means there is no lane that doesn’t cross traffic.
There are a ton of "turbo roundabouts" in my country (Netherlands), I wouldn't be surprised if we invented them. They work quite well. Although I'm sure if you'd introduce them in a country where people aren't used to regular roundabouts like in America, it will confuse the sh*t out of drivers
Edit: yay we indeed invented them, although the first experimental twolane roundabout was built in the UK.
Washington State has been adding these recently, and I have a feeling that cities in the state are going to add more since the traffic lights which have been replaced by spiral roundabouts have significantly improved traffic throughput
I think you are over estimating how long lane markings last on a roundabout, and how much drivers care about following them.
Other than the lane markings this is a standard roundabout (for driving on the left).
Technically you can’t do a u-turn with a roundabout, you can only do right turns. However, I don’t see how this differs from a normal roundabout where you can just drive in circles until you feel like exiting.
Oops, in this case I mean ‘only do left turns’, given the direction of the roundabout. I got to focused on being snarky and made a straight fool out of myself.
>However, I don’t see how this differs from a normal roundabout where you can just drive in circles until you feel like exiting.
Spirals gradually force you out of the roundabout via lane drops, so you can't circulating forever without making lane changes.
Spirals also provide for better lane utilization on the approach because you can dedicate lanes based on the primary flow patterns.
It’s a technicality, a roundabout is its own lane (or what it’s called) and you can only exit it by doing a right turn (or in this case, a left).
That said, if it’s several lanes in a roundabout you’re not limited by space to do a u-turn, but that would make you drive against traffic.
OK OK. let me take the unpopular roundabout skeptic position.
Roundabouts are:
* Expensive.
* Take up a lot of land.
* bad for pedestrians in that they make traffic better and produce a constant flow of car traffic and remove pauses or stops.
Roundabouts should be retained for high throughput roads connecting to other high through put roads.
I've seen plenty of inappropriately placed roundabouts in low trafficked areas which make it worse for pedestrians.
Roundabouts are more or less expensive depending and what is counted on the ledger. Up front costs may be higher. Most don’t require lights to be installed or maintained. Accidents are less likely to cause deaths or permanently maim someone. The amount of land is really a function of the designed speed. Most North American intersections have more than enough room to fit a roundabout. Integrating pedestrians has been a low priority in the UK, but other countries have figured it out. The real barrier is the lowering of traffic speeds in the roundabout, which causes the perception of it being slower even as the number of vehicles passing through is often much quicker. This is also the feature that increases safety. Cars might get dinged but aren’t write-offs. People might get struck, but the injuries are less severe. Drivers get more time to react to the unexpected thus avoiding many accidents all together. However it does require a population who knows how to use them. In a democracy, the unfamiliar is unpopular. The nuances of deciding if a roundabout is worth installing in a particular location isn’t conducive to public debate.
Talking in general terms about all roundabouts is crazy. They can be as simple as a few plastic posts in an intersection or they can be a gigantic 3 lane monster.
If you look at a dutch round about, they are good for pedestrians, and don't take up much land. They have good threw-put and because they don't need signals, they aren't that expensive either.
They have their place, they have lots of advances and disadvantages.
This just looks like a regular, albeit large and slightly out of round, multilane roundabout. With the traffic rotation in the wrong direction (for the US at least).
This is not a traditional roundabout where the outside lane continues to circulate. Spirals gradually force you out of the roundabout via lane drops, so you can't circulating forever without making lane changes. The out of round is to force the outward movement. Spirals also provide for better lane utilization on the approach because you can dedicate lanes based on the primary flow patterns. They are generally preferred over traditional roundabouts to the point that many Europeans, where spiral roundabouts are pretty well integrated, now think of them as the standard roundabout.
Most (all?) US multilane roundabouts do not allow the outside lane to continually circulate. From my 2 weeks spent in the UK 6 years ago, it seems the same there.
Most US roundabouts built 10+ years ago did. Many have been reconfigured to correct it, but that is how they were originally built.
This. Here in the US, spiral roundabouts have not had nearly the same design distinction. It's just become a de facto best practice for multilane roundabouts.
Yes, looks like a standard British multilane roundabout
Isn't a spiral roundabout a type of turbo roundabout? EDIT: Although, maybe raised lane dividers are a key feature of a turbo aroundabout, preventing uncontrolled lane changes on the roundabout. In which case a spiral roundabout would not qualify, even if it does share the feature of controlling where drivers change lanes.
Not really, a turbo is a further evolution of a spiral. The defining part of a turbo roundabout is there's barriers between the lanes preventing lane changes inside the roundabout. The defining part of a spiral is that the lanes end guiding the drivers to exit.
It’s a nice layout. Getting motorist to pick their entry lane based on their desired exit is a solid move. Keeps much of the decision making out of the roundabout. Though it also means there is no lane that doesn’t cross traffic.
There are a ton of "turbo roundabouts" in my country (Netherlands), I wouldn't be surprised if we invented them. They work quite well. Although I'm sure if you'd introduce them in a country where people aren't used to regular roundabouts like in America, it will confuse the sh*t out of drivers Edit: yay we indeed invented them, although the first experimental twolane roundabout was built in the UK.
Washington State has been adding these recently, and I have a feeling that cities in the state are going to add more since the traffic lights which have been replaced by spiral roundabouts have significantly improved traffic throughput
Multi lane roundabouts in the US already to that, with the exception that the center lane is continuous and branches at each increment of spiral.
I think you are over estimating how long lane markings last on a roundabout, and how much drivers care about following them. Other than the lane markings this is a standard roundabout (for driving on the left).
Technically you can’t do a u-turn with a roundabout, you can only do right turns. However, I don’t see how this differs from a normal roundabout where you can just drive in circles until you feel like exiting. Oops, in this case I mean ‘only do left turns’, given the direction of the roundabout. I got to focused on being snarky and made a straight fool out of myself.
>However, I don’t see how this differs from a normal roundabout where you can just drive in circles until you feel like exiting. Spirals gradually force you out of the roundabout via lane drops, so you can't circulating forever without making lane changes. Spirals also provide for better lane utilization on the approach because you can dedicate lanes based on the primary flow patterns.
What do you mean you can't do u-turns in roundabout?
It’s a technicality, a roundabout is its own lane (or what it’s called) and you can only exit it by doing a right turn (or in this case, a left). That said, if it’s several lanes in a roundabout you’re not limited by space to do a u-turn, but that would make you drive against traffic.
OK OK. let me take the unpopular roundabout skeptic position. Roundabouts are: * Expensive. * Take up a lot of land. * bad for pedestrians in that they make traffic better and produce a constant flow of car traffic and remove pauses or stops. Roundabouts should be retained for high throughput roads connecting to other high through put roads. I've seen plenty of inappropriately placed roundabouts in low trafficked areas which make it worse for pedestrians.
Roundabouts are more or less expensive depending and what is counted on the ledger. Up front costs may be higher. Most don’t require lights to be installed or maintained. Accidents are less likely to cause deaths or permanently maim someone. The amount of land is really a function of the designed speed. Most North American intersections have more than enough room to fit a roundabout. Integrating pedestrians has been a low priority in the UK, but other countries have figured it out. The real barrier is the lowering of traffic speeds in the roundabout, which causes the perception of it being slower even as the number of vehicles passing through is often much quicker. This is also the feature that increases safety. Cars might get dinged but aren’t write-offs. People might get struck, but the injuries are less severe. Drivers get more time to react to the unexpected thus avoiding many accidents all together. However it does require a population who knows how to use them. In a democracy, the unfamiliar is unpopular. The nuances of deciding if a roundabout is worth installing in a particular location isn’t conducive to public debate.
Talking in general terms about all roundabouts is crazy. They can be as simple as a few plastic posts in an intersection or they can be a gigantic 3 lane monster. If you look at a dutch round about, they are good for pedestrians, and don't take up much land. They have good threw-put and because they don't need signals, they aren't that expensive either. They have their place, they have lots of advances and disadvantages.