At first, I always took the three words to be synonymous.
I am thinking that “rotary” is more akin to a British “gyratory.” In other words, a more broad meaning which would mean any type of junction where traffic rotates around something. I have heard this triangular road in Skowhegan, Maine called a rotary; but it really doesn’t seem to function in the same way as what I have always thought of as a traditional rotary.
Would it be accurate linguistically (or technically) to say that a roundabout and a traffic circle are subsets of the broader definition above? Could I say “all roundabouts are rotaries, but not all rotaries are roundabouts” and be correct? Incidentally, the signs for rotaries in Maine have never used the word as a noun, always an adjective (“Rotary Junction” is the usual sign), but in common speech, it’s used as a noun.
A dumb question I suppose; except I thrive on a certain amount of useless trivia.
“The word roundabout dates from the early twentieth century,[1] In the U.S., the term traffic circle is used where entering traffic is either controlled by stop signs, traffic signals, or is not formally controlled at all and speed of vehicles may remain unchanged. The term, roundabout, is reserved for circular flow intersections where entering traffic must yield to traffic already in device,”
I think of a rotary and a roundabout being the same thing, just American (well, New England) and British. Generally, they will have more than 2 roads intersecting.
A traffic circle… I think of as two roads intersecting, but with a circle in it often to slow traffic down and make the intersection safer.
On a normal British roundabout, traffic entering the roundabout always yields to traffic already traversing it. I’m not sure that’s true of all the other circular traffic systems in other parts of the world.
Well, here in New England, the word roundabout has only been around for the past few years. But rotary and traffic circle have been common. The things I see called “roundabouts” by the state DOT tend to be much smaller than a typical rotary. Compare this roundabout in Bangor, Maine with this rotary in Windham, Maine. The rotary in Windham could also be called a traffic circle, but the thing I linked in the OP, while the natives of Skowhegan call it a rotary, I would certainly not call it a roundabout or a traffic circle. That’s what made me wonder if rotary were just a broader category for intersections where cars have to “rotate” around something, with traffic circles and roundabouts having more specific meanings.
The only exception anywhere in the world that I know of (there could of course be others, but this is the most famous one) is the Place de l’Etoile, around the Arc de Triomphe. Entering traffic has the right of way. Fun to watch from the top of the Arc de Triomphe, but it must be a nightmare to be in the middle of it.
I don’t understand why anyone would choose to set it up that way. It’s like asking for gridlock. When the circle has the right of way, everyone only has to yield once, no matter which way they are going. With the circle having to yield, the further around you are going, the more times you’re going to have to yield.
I suppose it’s a good idea if your goal is to create, rather than alleviate, gridlock.
It does make sense, though, if you need to maximize circle capacity. It is like the logic of right-of-way: at an uncontrolled intersection, you yield to the car on your right because that car is about to cross your path now whereas you have to cross half the intersection before you are about to cross their path. If you are turning right, you have to yield to no one, if you are going straight, you have to yield once, left twice, so it really cannot be that big a deal. Now if we could somehow reduce the number of discourteous sociopaths on the road, these things might work really well.
Traffic circles, or rotaries, are much larger than modern roundabouts. Traffic circles often have stop signs or traffic signals within the circular intersection. The Arc de Triomphe in Paris and Dupont Circle in Washington, D.C., are two examples of older-style traffic circles.
Neighborhood traffic calming circles are much smaller than modern roundabouts and often replace stop signs at four-way intersections. They are typically used in residential neighborhoods to slow traffic speeds and reduce accidents, but are typically not designed to accommodate larger vehicles.
Modern roundabouts are designed to accommodate vehicles of all sizes, including emergency vehicles, buses, and truck and trailer combinations. In a modern roundabout, drivers enter the intersection by navigating a gentle curve. Drivers yield at entry to traffic already in the roundabout, then proceed into the intersection and exit at their desired street.
That’s the rule in Spain. Exceptions exist when the circle is so large and has so many important streets running up to it that the whole thing is semaphore-managed, but that’s because semaphores trump general rules-of-way.
Just in the last few days I’ve gotten quite interested in roundabouts. They completed one in my county earlier this year and it’s done wonders for reducing traffic backups at that intersection. Unfortunately, that intersection is way out in the country away from the city. The only time I go through it is on bike rides – it doesn’t help at all for driving around town. I’d like to convince the local authorities to replace some of the traffic lights with them, but am uncertain of the best way to proceed.
As far as I’m concerned, a circular intersection needs several features to be considered a roundabout:
yield/give-way signs on the approaches.
splitter islands to separate the incoming and outgoing lanes. These slow incoming traffic and change its direction to being tangental to the circle rather than at right angles.
pedestrian crossings a car-length away from the circle and which use the splitter islands as refuge in the middle of the crossing. Pedestrians then have to look only one way at a time when crossing.
Without these features (and anything made before about the mid-60s usually doesn’t have them) it’s just a traffic circle.
As I said, I’d like to convince the county and cities here to put more of them in. There’s only 10 in the entire county I live in, which is a drop in the bucket compared to the number of traffic signals. Ideally, I’d like this area to be like Carmel, Indiana where they’re replacing just about every traffic light in town with them. But that has the mayor of the city behind it.
I’m not sure there is a real technical distinction but from my UK perspective I’d tend to generally agree with you and my terminology is thus:
A gyratory/rotary always suggest a larger, circular system often with multiple junctions and traffic lights. example here
A roundabout/traffic circle is smaller in scale. Three or four entries/exits with simple junctions at each.
Of course there are some roundabouts that are simple but large in scale and may have lights on a temporary or permanent basis.
So it is obvious to me when I’m looking at a “gyratory” system, and also when I’m looking at a simple roundabout, but where the line is drawn? I don’t know.
But that’s going to have the opposite effect. If the person entering the circle has the right of way, and traffic is heavy, the circle is going to gridlock, because cars on it aren’t going to be able to exit to make room. When the traffic in the circle has the right of way, they yield once, and get to keep going until they leave. Their space is quickly vacated to make room for additional traffic.
It’s kind of like the courtesy we follow at an elevator. We wait for people leaving it before we enter, else it’ll get too crowded.
If traffic in that circle linked above had the right of way, they could clear out to make room for more cars. But in that image, they grind to a halt, because cars coming from Point A must wait for B to get out of the way. B can’t get out of the way until C does. C must wait for D. And then there’s D, which must wait for A to move. In other words, A is ultimately waiting A.
That gridlock at that location would likely be reduced sharply just by giving traffic in the circle the right of way.
The only thing I can think of being called a gyratory in the UK is the Hangar Lane gyratory in London. I looked it up on Google maps and it’s no bigger or more complex that other things just called roundabouts. The Shepherd & Flock roundabout in Farnham is big enough to have several houses and a pub in it!
