What do you think. Would this example be considered a modern roundabout or a traffic circle?
https://www.google.com/maps/@44.3103965,-69.7791636,81m/data=!3m1!1e3
Quote from: tradephoric on May 08, 2015, 04:57:37 PM
What do you think. Would this example be considered a modern roundabout or a traffic circle?
https://www.google.com/maps/@44.3103965,-69.7791636,81m/data=!3m1!1e3
I'd say a roundabout.
I was going to say...
If it looks like a dog, walks like a dog and barks like a dog, then it's a dog.
But I think this more accurate:
If it looks like a horse, walks like a dog, and barks like a dog, then it's a dog-horse.
Basically, it fails the requirement for both. It's not a traffic circle since it's painted like a modern roundabout with proper right-of-way signing, but it's too big to legally fit the MUTCD's opinion of what a modern roundabout should be (I believe they cite a 200' max diameter). That said, if I had to lean towards one or the other, I'd definitely say roundabout.
All roundabouts are traffic circles.
Quote from: tradephoric on May 08, 2015, 04:57:37 PM
What do you think. Would this example be considered a modern roundabout or a traffic circle?
https://www.google.com/maps/@44.3103965,-69.7791636,81m/data=!3m1!1e3
It's a "roundabout", but as far as I'm concerned, the terms are synonymous.
Now that there are MUTCD standards for roundabouts, I think this would be classified as one. Aren't traffic circles from the 20th century?
In all possible ways it is a modern roundabout.
Roundabout.
It's not that much bigger (if at all) than 200' surely? And even then it functions like a roundabout - circulating traffic has priority.
Plus Europe has many bigger roundabouts than that (while still not overly common outside of Grade-separated junctions).
Roundabout.
Looks way safer than New Jersey's death circles, so I'll say roundabout.
Hmm. Taking a second look, especially after english si's suggestion, it's definitely just a modern roundabout. I thought it was much bigger than it was, but the circle only has an inscribed diameter of 215'. Which is big, but certainly not obnoxious.
High-capacity (non-motorway) roundabouts are typically in the range 60-90 m, so nothing unusual really. The roundabout seems to lack roundabout signs though, so depending on how an intersection legally is determined to be a roundabout, it's possible that it isn't one.
Looks to me like a rotary later modified to emulate modern roundabout operations.
The geometry of the circle is pretty much the same today as it was in 1956 (when looking at historical imagery on NETR). It's tough to tell at what point a traffic circle can be considered a modern roundabout. Did it become a modern roundabout when the lanes were re-striped? Assuming the circle has always been yield control at entry, could this be considered the first modern roundabout in America?
There are three things it could be... Traffic Circle, Roundabout, or Rotary. Given there do not appear to be any traffic control devices, i.e. Traffic Signals or Stop Lights, nor is right of way given to those entering the circle, it is not a traffic circle. Given that traffic entering has to yield to traffic in the circle, and the speed limit is logical city speeds, it is a Roundabout. If it operated at higher speeds, it could qualify as a rotary.
Example of a Rotary...
https://www.google.com/maps/place/Pictou,+NS,+Canada/@45.6823814,-62.7312622,735m/data=!3m1!1e3!4m2!3m1!1s0x4b5ea1c8b6b56277:0xd3026362ae656532!6m1!1e1 (https://www.google.com/maps/place/Pictou,+NS,+Canada/@45.6823814,-62.7312622,735m/data=!3m1!1e3!4m2!3m1!1s0x4b5ea1c8b6b56277:0xd3026362ae656532!6m1!1e1)
Note how there does not appear to be any reduced speed for this rotary, which the approaching roads are traveling, at east on the TCH, at 100 KPH.
Many people confuse other and older styles of circular intersections with modern roundabouts. East coast rotaries, large multi-lane traffic circles (Arc D'Triomphe, Dupont Circle), and small neighborhood traffic circles are not modern roundabouts. If you want to see the difference between a traffic circle, a rotary (UK roundabout) and a modern roundabout (UK continental roundabout), go to http://tinyurl.com/kstate-RAB to see pictures. And here's another site that shows the difference between an older rotary and a modern roundabout: http://tinyurl.com/bzf7qmg
If the entry lane has a stop sign, it's not a modern roundabout.
If you could play a game of football in the center landscaped area, it's not a modern roundabout.
If the circular roadway has a stop sign, yield sign or signal, it's not a modern roundabout.
If you don't have to slow down to enter it, it's not a modern roundabout.
If you have to change lanes in the circular roadway to exit, it's not a modern roundabout.
If you can easily drive faster than 20 mph in the circular roadway, it's not a modern roundabout.
If it has a park for pedestrians, or a building, in the middle, it's not a modern roundabout.
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
Many people confuse other and older styles of circular intersections with modern roundabouts. East coast rotaries, large multi-lane traffic circles (Arc D'Triomphe, Dupont Circle), and small neighborhood traffic circles are not modern roundabouts. If you want to see the difference between a traffic circle, a rotary (UK roundabout) and a modern roundabout (UK continental roundabout), go to http://tinyurl.com/kstate-RAB to see pictures. And here's another site that shows the difference between an older rotary and a modern roundabout: http://tinyurl.com/bzf7qmg
If the entry lane has a stop sign, it's not a modern roundabout.
If you could play a game of football in the center landscaped area, it's not a modern roundabout.
If the circular roadway has a stop sign, yield sign or signal, it's not a modern roundabout.
If you don't have to slow down to enter it, it's not a modern roundabout.
If you have to change lanes in the circular roadway to exit, it's not a modern roundabout.
If you can easily drive faster than 20 mph in the circular roadway, it's not a modern roundabout.
If it has a park for pedestrians, or a building, in the middle, it's not a modern roundabout.
So what about the example i originally posted. Is it or is it not a modern roundabout in your opinion?
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If the entry lane has a stop sign, it's not a modern roundabout.
True.
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If you could play a game of football in the center landscaped area, it's not a modern roundabout.
False. What's inside the roundabout central area has no bearing on whether it's a roundabout or not.
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If the circular roadway has a stop sign, yield sign or signal, it's not a modern roundabout.
True.
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If you don't have to slow down to enter it, it's not a modern roundabout.
Depends. Large roundabouts with little to no traffic can allow entering at full speed. For example, taking the first exit here (https://www.google.se/maps/@58.42335,15.667195,3a,66.8y,49.5h,88.17t/data=!3m4!1e1!3m2!1szCAfbH535_520OyslDjptA!2e0) is easily done at 70 km/h if there is no traffic coming at the moment.
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If you have to change lanes in the circular roadway to exit, it's not a modern roundabout.
Depends on how you mean. If you mean there is a parallel lane like in a cloverleaf interchange, then it's true, otherwise false (multi-lane roundabouts).
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If you can easily drive faster than 20 mph in the circular roadway, it's not a modern roundabout.
False. Most modern roundabouts are designed for a speed of about 30 km/h, but there are many larger or older roundabouts that allow speeds of 50 km/h, even 70 km/h in some cases depending on where you're going.
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If it has a park for pedestrians, or a building, in the middle, it's not a modern roundabout.
False. Again, what's inside the roundabout central area has no bearing on whether it's a roundabout or not.
To prove my point, here's (https://www.google.se/maps/@58.4063292,15.5829215,18z) a roundabout with a diameter of about 200 m. While there is no football field or building inside the central area, there is enough space, and the area is used as a park from time to time. The roundabout's size allows traffic to go at 50 km/h with ease. All entrances are signed with the Vienna Convention roundabout sign as well as yield signs and shark teeth markings. It is also legally defined as a roundabout in the local traffic code.
Part of the problem in this thread is that there's a FHWA definition of "(modern) roundabout" that's substantially narrower than what the term "roundabout" is used for in practice in countries that have a longer history of building "modern" roundabouts, as opposed to old-school rotaries/traffic circles. So, for example, you'll find hundreds of roundabouts in the UK that are signed at the national speed limit (60 or 70 mph) and will have circulating traffic at speeds that by US standards would be considered rotary-like.
Would a modern US engineer, tasked with creating a roundabout, design the circular intersection in the first post? Probably not. At the very least, it would feature turbine-style striping (hardly ever used in the UK - indeed, multilane roundabouts often lack striping at all!), more elaborate provision for pedestrians (at the very least, crosswalks at right-angles to traffic) and perhaps even cyclists, some sort of truck apron (because FHWA said so!), deliberate calming of entering traffic like a sharper entry angle, and less elaborate landscaping within the circle on the grounds of it being a collision hazard. And Grove Street would be cul-de-saced (or at least channelized) so there's no chance of traffic from it entering the circular roadway without at least mounting a curb.
That said, I think it fits the common-sense definition of a "roundabout" even if FHWA guidance would frown on some of its specific design features.
It conforms to modern roundabout standards, apart from the entries.
The entries are more tangent than is preferred. Drivers should perceive the need to slow down before entering at a modern roundabout.
Modern roundabouts, in the US, are low speed intersections that do not typically operate faster than 20 mph (aka, 30 kph). As diameters get larger, vehicle speeds in the circular roadway increase and make it difficult for entering traffic to get in. This is the issue with east coast rotaries, and one of the reasons the US walked away from them. The circulating speeds conflict with entering speeds and crashes were the result.
The UK did not walk away, but continued to tinker with the concept, eventually reducing the circular roadway diameter and adopting the yield on entry rule (in the UK called the offside priority rule, look up Frank Blackmore).
Quote from: riiga on May 11, 2015, 04:42:45 PM
To prove my point, here's (https://www.google.se/maps/@58.4063292,15.5829215,18z) a roundabout with a diameter of about 200 m. While there is no football field or building inside the central area, there is enough space, and the area is used as a park from time to time. The roundabout's size allows traffic to go at 50 km/h with ease. All entrances are signed with the Vienna Convention roundabout sign as well as yield signs and shark teeth markings. It is also legally defined as a roundabout in the local traffic code.
That would not be considered in any way, shape, or form a roundabout in the US. Looks more like one of the old rotories.
Incidentally, I have been able to go faster than 20 mph in some multi-lane roundabouts, though the one I do so most frequently (Latham Circle) is actually a retrofitted traffic circle.
There's also one around here that appears to have a truck apron in the truck apron.
https://www.google.com/maps/@42.713117,-73.808284,3a,32.3y,300.89h,76.12t/data=!3m4!1e1!3m2!1sZTWDtRdnxt_k0OGj7AIrog!2e0
Quote from: riigaFalse. What's inside the roundabout central area has no bearing on whether it's a roundabout or not.
While you are technically correct, having a space large enough to play football (or soccer) in the middle means it would break FHWA's definition of a modern roundabout, as noted by lordsutch.
Quote from: riiga on May 11, 2015, 04:42:45 PM
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If you have to change lanes in the circular roadway to exit, it's not a modern roundabout.
Depends on how you mean. If you mean there is a parallel lane like in a cloverleaf interchange, then it's true, otherwise false (multi-lane roundabouts).
A properly-designed, multi-lane modern roundabout does not require a lane change to exit. The markings within the circulating roadway should channel drivers outwards as appropriate.
Quote from: froggie on May 11, 2015, 10:03:21 PM
Quote from: riiga on May 11, 2015, 04:42:45 PM
False. What's inside the roundabout central area has no bearing on whether it's a roundabout or not.
While you are technically correct, having a space large enough to play football (or soccer) in the middle means it would break FHWA's definition of a modern roundabout, as noted by lordsutch.
Specifically, by FHWA definition, modern roundabouts disallow any pedestrian activity on the central island. So having a space large enough to invite pedestrian activity to the center disqualifies it as a modern roundabout.
Quote from: roadfro on May 16, 2015, 06:29:20 PM
Quote from: riiga on May 11, 2015, 04:42:45 PM
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If you have to change lanes in the circular roadway to exit, it's not a modern roundabout.
Depends on how you mean. If you mean there is a parallel lane like in a cloverleaf interchange, then it's true, otherwise false (multi-lane roundabouts).
A properly-designed, multi-lane modern roundabout does not require a lane change to exit. The markings within the circulating roadway should channel drivers outwards as appropriate.
Then in that case, any two-lane circles/rotaries/roundabouts do not qualify as modern roundabouts. Why have the inside lane, then, which would require two lane changes, to enter the lane and then to exit the roundabout?
Oh look, Hibby hates what he doesn't understand.
Quote from: hbelkins on May 16, 2015, 06:55:52 PM
Quote from: roadfro on May 16, 2015, 06:29:20 PM
Quote from: riiga on May 11, 2015, 04:42:45 PM
Quote from: ScottRAB on May 11, 2015, 03:37:40 PM
If you have to change lanes in the circular roadway to exit, it's not a modern roundabout.
Depends on how you mean. If you mean there is a parallel lane like in a cloverleaf interchange, then it's true, otherwise false (multi-lane roundabouts).
A properly-designed, multi-lane modern roundabout does not require a lane change to exit. The markings within the circulating roadway should channel drivers outwards as appropriate.
Then in that case, any two-lane circles/rotaries/roundabouts do not qualify as modern roundabouts. Why have the inside lane, then, which would require two lane changes, to enter the lane and then to exit the roundabout?
The lanes are striped such that the inner lane moves outward at the major exits.
https://www.google.com/maps/@42.636931,-73.8562964,150m/data=!3m1!1e3
If I had run across this while driving, or seen the picture without context, I would have called it a roundabout.
Quote from: hbelkins on May 16, 2015, 06:55:52 PM
A properly-designed, multi-lane modern roundabout does not require a lane change to exit. The markings within the circulating roadway should channel drivers outwards as appropriate.
Such markings are typically used in turbo roundabouts, while regular roundabouts don't have them. I guess (multi-lane) modern American roundabouts are more turbo roundabout like than standard multi-lane roundabouts. Standard multi-lane roundabout. (http://www.hitta.se/kartan!~58.41237,15.65357,19z/tr!i=PSPn23vR/tileLayer!l=1) Turbo roundabout. (https://www.google.se/maps/@51.8484648,4.0884797,20z/data=!3m1!1e3)
QuoteThen in that case, any two-lane circles/rotaries/roundabouts do not qualify as modern roundabouts. Why have the inside lane, then, which would require two lane changes, to enter the lane and then to exit the roundabout?
Not true. Plenty of 2-lane roundabouts where you can legally (and via striping) exit from the inside lane.
Quote from: lordsutch on May 11, 2015, 05:41:06 PMSo, for example, you'll find hundreds of roundabouts in the UK that are signed at the national speed limit (60 or 70 mph)
The UK doesn't put specific speed limits for merely the duration of the intersection.
I believe the limit is 60mph, as a one-way road, rather than a dual carriageway. There's only a small number of roundabouts where that is possible to travel around the roundabout at that speed* - typically traffic signals have been added to busy large roundabouts, though sometimes smaller roundabouts have been added to make 'magic roundabouts' (and, in the case of Denham Roundabout, M40 J1: some of both).
*Rather than just plowing through taking a 'racing line' straight through. I've endured a driver doing ~100mph on the A43 who only slowed down a little for the roundabouts as it was empty and he could take the path of least deflection. Still was a jolt left followed by a jolt right and not comfortable.
Quote from: riiga on May 17, 2015, 05:35:10 AM
Quote from: hbelkins on May 16, 2015, 06:55:52 PM
A properly-designed, multi-lane modern roundabout does not require a lane change to exit. The markings within the circulating roadway should channel drivers outwards as appropriate.
Such markings are typically used in turbo roundabouts, while regular roundabouts don't have them. I guess (multi-lane) modern American roundabouts are more turbo roundabout like than standard multi-lane roundabouts. Standard multi-lane roundabout. (http://www.hitta.se/kartan!~58.41237,15.65357,19z/tr!i=PSPn23vR/tileLayer!l=1) Turbo roundabout. (https://www.google.se/maps/@51.8484648,4.0884797,20z/data=!3m1!1e3)
The "standard multi-lane" is considered a traffic circle on this side of the pond. The Turbo one looks like a modern roundabout with a barrier between lanes and a non-circular center island.
QuoteThe "standard multi-lane" is considered a traffic circle on this side of the pond.
If you consider that inside "sidewalk" to be a truck apron and adjust the lane striping to MUTCD-standard, then I would say yes that's more a roundabout than a traffic circle.
Quote from: riiga on May 17, 2015, 05:35:10 AM
Such markings are typically used in turbo roundabouts, while regular roundabouts don't have them. I guess (multi-lane) modern American roundabouts are more turbo roundabout like than standard multi-lane roundabouts. Standard multi-lane roundabout. (http://www.hitta.se/kartan!~58.41237,15.65357,19z/tr!i=PSPn23vR/tileLayer!l=1) Turbo roundabout. (https://www.google.se/maps/@51.8484648,4.0884797,20z/data=!3m1!1e3)
Washington State used to have a modern roundabout painted like your first example, and WSDOT noticed that no one was using the inside lane because they felt obligated to exit only from the outside lane. You can see the "cat tracks" are much heavier in the outside lane.
Some might say that this isn't a modern roundabout, but WSDOT's chief engineer Brian Walsh says it is, given the entry deflection and that it was built circa 2001. Unlike later designs, these earlier roundabouts used European guidelines, hence the pavement markings. Later designs used Aussie design standards.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FXbJmYp9.png&hash=992c943f284ea4f0bf22b6daa8cf9f0a24866c7e)
Gig Harbor, WA / WA-16 at Burnham Drive (https://goo.gl/4rHeCz)
As much as I like this traditional design, I would rather have no lanes lines than non-spiraling lines. Here's my preferences, in order from most to least preferred, for pavement markings:
1. no lane lines
2. spiral/turbo lane lines
3. traditional style
Quote from: jakeroot on May 17, 2015, 07:35:43 PM
Some might say that this isn't a modern roundabout, but WSDOT's chief engineer Brian Walsh says it is, given the entry deflection and that it was built circa 2001.
It has some features making it a modern roundabout, but it's not. There's no point where the inside lane directs people to an exit.
And it's a modern roundabout because it was built in 2001? Um...
Quote from: jeffandnicole on May 17, 2015, 07:39:56 PM
Quote from: jakeroot on May 17, 2015, 07:35:43 PM
Some might say that this isn't a modern roundabout, but WSDOT's chief engineer Brian Walsh says it is, given the entry deflection and that it was built circa 2001.
It has some features making it a modern roundabout, but it's not. There's no point where the inside lane directs people to an exit.
"Modern" in context; the design was considered state of the art (by European standards) when it was constructed.
Quote from: jeffandnicole on May 17, 2015, 07:39:56 PM
And it's a modern roundabout because it was built in 2001? Um...
Traffic circles were essentially dead before the turn of the century. Most roundabouts built since the 90s were built with "modern roundabout" intentions, as far as I'm concerned.
QuoteIt has some features making it a modern roundabout, but it's not. There's no point where the inside lane directs people to an exit.
Mainly because the striping is subpar, but one could technically exit from the inside lane to the east/right-side-of-the-image.
QuoteAnd it's a modern roundabout because it was built in 2001? Um...
That's around the time that modern roundabouts began to take root in the U.S. MnDOT built their first in 2002.
Quote from: froggie on May 18, 2015, 10:14:54 AM
That's around the time that modern roundabouts began to take root in the U.S. MnDOT built their first in 2002.
By 2002, there was roughly 400 modern roundabouts in the US. Colorado built a lot of modern roundabouts before 2000.
Here's a link to the FHWA typical lane markings of Modern Roundabouts.
Picture diagrams from the MUTCD: http://mutcd.fhwa.dot.gov/htm/2009/part3/part3c.htm
The lane use signs and lane markings should reinforce each other and tell people driving which lane can do what. You choose the lane to enter an intersection based on where you want to end up, just like at a signalized intersection.