Modern roundabout or Traffic Circle?

[tradephoric]

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

[tribar]

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.

[jakeroot]

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.

[NE2]

All roundabouts are traffic circles.

[Brandon]

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.

[Buffaboy]

Now that there are MUTCD standards for roundabouts, I think this would be classified as one. Aren't traffic circles from the 20th century?

[riiga]

In all possible ways it is a modern roundabout.

[english si]

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).

[jeffandnicole]

Roundabout.

[Zeffy]

Looks way safer than New Jersey's death circles, so I'll say roundabout.

[jakeroot]

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.

[riiga]

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.

[roadfro]

Looks to me like a rotary later modified to emulate modern roundabout operations.

[tradephoric]

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?

[TEG24601]

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


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.

[ScottRAB]

   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.

[tradephoric]

   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?

[riiga]

If the entry lane has a stop sign, it's not a modern roundabout.

True.

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.

If the circular roadway has a stop sign, yield sign or signal, it's not a modern roundabout.

True.

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 is easily done at 70 km/h if there is no traffic coming at the moment.

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).

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.

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 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.

[lordsutch]

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.

[ScottRAB]

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).

[vdeane]

To prove my point, here's 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

[froggie]

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.

[roadfro]

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.

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.

[hbelkins]

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?

[NE2]

Oh look, Hibby hates what he doesn't understand.