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National Boards => General Highway Talk => Topic started by: tradephoric on February 07, 2019, 09:48:16 AM

Title: Over 7000 roundabouts in America
Post by: tradephoric on February 07, 2019, 09:48:16 AM
Here is a Google Earth KMZ file that contains over 6000 modern roundabouts in America.

http://www.mediafire.com/file/j6zcvi91whg3j2u/Roundabouts+%282019-02-12%29.kmz
Title: Re: Over 6000 roundabouts in America
Post by: formulanone on February 07, 2019, 11:18:32 AM
If you're not a traffic light salesman, we'll help you conquer your obsessive fear of roundabouts.
Title: Re: Over 6000 roundabouts in America
Post by: cabiness42 on February 07, 2019, 12:11:44 PM
Only half of those are in Carmel, IN.
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 07, 2019, 12:24:29 PM
They're all crash-prone.
Title: Re: Over 6000 roundabouts in America
Post by: TechZeke on February 07, 2019, 01:18:18 PM
I can deal with roundabouts; it's the other idiots that can't seem to figure out how to properly yield that make them unpleasant for me. I have to pray that I don't get cut off from when another car approaches when I'm already in the roundabout.
Title: Re: Over 6000 roundabouts in America
Post by: abefroman329 on February 07, 2019, 01:31:32 PM
I can deal with roundabouts; it's the other idiots that can't seem to figure out how to properly yield that make them unpleasant for me. I have to pray that I don't get cut off from when another car approaches when I'm already in the roundabout.
Come to Chicago, where they installed roundabouts as traffic-calming measures on certain streets, but didn't provide any signage on how to use them, and consequently, many drivers make a left-hand turn by turning left at the roundabout.
Title: Re: Over 6000 roundabouts in America
Post by: froggie on February 07, 2019, 01:33:29 PM
^ Some of that could also just be Chicago/Illinois drivers.  You guys tend to be arseholes on the road....almost as bad as mAss or DC drivers...
Title: Re: Over 6000 roundabouts in America
Post by: abefroman329 on February 07, 2019, 01:54:15 PM
^ Some of that could also just be Chicago/Illinois drivers.  You guys tend to be arseholes on the road....almost as bad as mAss or DC drivers...
Nah, this is a total Maryland driver move.
Title: Re: Over 6000 roundabouts in America
Post by: kalvado on February 07, 2019, 02:14:05 PM
^ Some of that could also just be Chicago/Illinois drivers.  You guys tend to be arseholes on the road....almost as bad as mAss or DC drivers...
Yeah, US drivers seem to be much worse than average american driver.
And drivers on planet Earth are mostly crazy...
Title: Re: Over 6000 roundabouts in America
Post by: tradephoric on February 07, 2019, 02:25:21 PM
There are currently about 50 triple-lane roundabouts in America and roughly half of those are found in Wisconsin.  Green Bay alone has 10 triple-lane roundabouts.  Does anybody have any safety numbers out of Green Bay?  The city must keep track of the most dangerous intersections in the city (whether it be total crashes or a list weighted by severity).
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 07, 2019, 02:48:09 PM
Come to Chicago, where they installed roundabouts as traffic-calming measures on certain streets, but didn't provide any signage on how to use them, and consequently, many drivers make a left-hand turn by turning left at the roundabout.

Actual roundabouts, or just little bitty islands in the middle of the intersections?
Title: Re: Over 6000 roundabouts in America
Post by: Ben114 on February 07, 2019, 02:48:52 PM
A good chunk of those are in Cape Cod.
Title: Re: Over 6000 roundabouts in America
Post by: sparker on February 07, 2019, 03:44:58 PM
.............and another sizeable chunk out in the rural areas of CA (CA 43, CA 154/246 junction, etc.).  Not particularly beloved by truckers, to be sure!
Title: Re: Over 6000 roundabouts in America
Post by: Super Mateo on February 07, 2019, 03:46:24 PM
Come to Chicago, where they installed roundabouts as traffic-calming measures on certain streets, but didn't provide any signage on how to use them, and consequently, many drivers make a left-hand turn by turning left at the roundabout.

Actual roundabouts, or just little bitty islands in the middle of the intersections?

Tiny islands. 110th and Talman, for example. (https://www.google.com/maps/@41.6935593,-87.6872312,3a,75y,268.93h,90t/data=!3m6!1e1!3m4!1sUhTgeIPHvsNIpSD7HdXbPg!2e0!7i13312!8i6656?hl=en)
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 07, 2019, 03:48:52 PM


Come to Chicago, where they installed roundabouts as traffic-calming measures on certain streets, but didn't provide any signage on how to use them, and consequently, many drivers make a left-hand turn by turning left at the roundabout.

Actual roundabouts, or just little bitty islands in the middle of the intersections?

Tiny islands. 110th and Talman, for example. (https://www.google.com/maps/@41.6935593,-87.6872312,3a,75y,268.93h,90t/data=!3m6!1e1!3m4!1sUhTgeIPHvsNIpSD7HdXbPg!2e0!7i13312!8i6656?hl=en)

Well, assuming that's the type abefroman329 had in mind, then I don't see what's wrong with turning left in front of the little island.  I probably would.  The intersection you linked to, in fact, has stop signs on two approaches—just like a normal intersection.  That's not a roundabout, so why would people be expected to treat it like one?
Title: Re: Over 6000 roundabouts in America
Post by: Super Mateo on February 07, 2019, 03:53:51 PM


Come to Chicago, where they installed roundabouts as traffic-calming measures on certain streets, but didn't provide any signage on how to use them, and consequently, many drivers make a left-hand turn by turning left at the roundabout.

Actual roundabouts, or just little bitty islands in the middle of the intersections?

Tiny islands. 110th and Talman, for example. (https://www.google.com/maps/@41.6935593,-87.6872312,3a,75y,268.93h,90t/data=!3m6!1e1!3m4!1sUhTgeIPHvsNIpSD7HdXbPg!2e0!7i13312!8i6656?hl=en)

Well, assuming that's the type abefroman329 had in mind, then I don't see what's wrong with turning left in front of the little island.  I probably would.  The intersection you linked to, in fact, has stop signs on two approaches—just like a normal intersection.  That's not a roundabout, so why would people be expected to treat it like one?

If there's no traffic, I don't see the problem cutting through on a left turn.  There isn't that much traffic at this location, anyway.  There are roundabout signs on the approaches, but even then, I just treat it like a normal intersection.
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 07, 2019, 04:12:05 PM
Ah, I see the warning signs now.

Technically, warning signs don't tell you what to do, just what to watch out for.  I'm struggling to come up with any guidance in the Illinois Vehicle Code on what to do at a roundabout or traffic circle, so it's possible it's actually a legal loophole.
Title: Re: Over 6000 roundabouts in America
Post by: froggie on February 07, 2019, 04:32:13 PM
A good chunk of those are in Cape Cod.

Rotaries ≠ roundabouts

While both operate similarly in that traffic in the circle has right-of-way, rotaries in Mass are a noticeably larger radius than a roundabout.
Title: Re: Over 6000 roundabouts in America
Post by: kalvado on February 07, 2019, 04:55:12 PM
A good chunk of those are in Cape Cod.

Rotaries ≠ roundabouts

While both operate similarly in that traffic in the circle has right-of-way, rotaries in Mass are a noticeably larger radius than a roundabout.
Frankly speaking, there is no maximum roundabout diameter defined by FHWA. There are  minimum and recommended values (only for 4-leg 90 degree intersection), and mention of larger dimensions for high speed situations.  Larger diameters "should generally not be used", which is a pretty weak limit. 
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 07, 2019, 05:02:23 PM
These definitions are actually irrelevant to the topic at hand.  The 6000 figure posited by the OP came from a file with a specific data set.  Ben114's reply about a good chunk of them being on Cape Cod is therefore either objectively true or false.  If the data set doesn't include a sizable number of entries from Cape Cod, then he's wrong.  If it does, then he's right.

And more to the point of rotaries... if they are included in the data set, then they're part of the 6000.  If not, then they aren't.
Title: Re: Over 6000 roundabouts in America
Post by: MantyMadTown on February 07, 2019, 06:20:11 PM
Manitowoc, WI is also planning a roundabout at the intersection of WIS 42 and Maritime Dr. That one's not on the map.
https://projects.511wi.gov/waldo/full-project-overview/
Title: Re: Over 6000 roundabouts in America
Post by: jakeroot on February 07, 2019, 10:56:56 PM
^ Some of that could also just be Chicago/Illinois drivers.  You guys tend to be arseholes on the road....almost as bad as mAss or DC drivers...

I've never got the impression that District drivers were dickheads. What's the common arsehole move that you've seen?

My mother's primary complaint has been that drivers dilly-dally too much. Taxi's in particular.
Title: Re: Over 6000 roundabouts in America
Post by: froggie on February 07, 2019, 11:01:43 PM
Oh where should I start...

- Flagrant illegal parking
- Flagrant red light and stop sign running, despite the District having red light cameras.
- Flagrant speed.  While I'll agree that the DC area freeways could stand to have their 55 (or in the District's case, 45 or 50) limits reviewed, far too many drivers consider city streets their personal dragstrip and will rush upwards of 50 in a 25-or-30 in order to "beat the light".

Much more prevalent on the DC/MD side of the Potomac than on the Virginia side, though there are plenty of hotheads in Northern Virginia as well.
Title: Re: Over 6000 roundabouts in America
Post by: Road Hog on February 08, 2019, 12:14:01 AM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.
Title: Re: Over 6000 roundabouts in America
Post by: kalvado on February 08, 2019, 07:19:04 AM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.
not exactly, but close: NY85 - divided 4-lane 55 MPH, 3 roundabouts within 1 mile stretch.
https://www.google.com/maps/@42.6444845,-73.8563279,1384m/data=!3m1!1e3
Title: Re: Over 6000 roundabouts in America
Post by: tradephoric on February 08, 2019, 07:20:28 AM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.

This triple-lane roundabout in Wisconsin replaced a trumpet interchange about 10 years ago:

https://www.google.com/maps/@44.9210291,-91.3805333,156m/data=!3m1!1e3
Title: Re: Over 6000 roundabouts in America
Post by: US 89 on February 08, 2019, 08:55:15 AM
.............and another sizeable chunk out in the rural areas of CA (CA 43, CA 154/246 junction, etc.).  Not particularly beloved by truckers, to be sure!

California has state highway junctions as roundabouts? That’s really interesting.

I was just thinking about this yesterday, and realized that although there are lots of roundabouts in Utah, I can only think of two that carry a state highway: one at SR 224/Deer Valley Drive in Park City, and one on the University of Utah campus at Campus Center/South Campus (SR 282).

What I’ve noticed in Utah is that when routes get turned back to the city, often one of the first things the city does is install a roundabout or two on it. That happened to SR 140, SR 73...
Title: Re: Over 6000 roundabouts in America
Post by: abefroman329 on February 08, 2019, 09:05:01 AM


Come to Chicago, where they installed roundabouts as traffic-calming measures on certain streets, but didn't provide any signage on how to use them, and consequently, many drivers make a left-hand turn by turning left at the roundabout.

Actual roundabouts, or just little bitty islands in the middle of the intersections?

Tiny islands. 110th and Talman, for example. (https://www.google.com/maps/@41.6935593,-87.6872312,3a,75y,268.93h,90t/data=!3m6!1e1!3m4!1sUhTgeIPHvsNIpSD7HdXbPg!2e0!7i13312!8i6656?hl=en)

Well, assuming that's the type abefroman329 had in mind, then I don't see what's wrong with turning left in front of the little island.  I probably would.  The intersection you linked to, in fact, has stop signs on two approaches—just like a normal intersection.  That's not a roundabout, so why would people be expected to treat it like one?
I'm talking about something like this: https://www.google.com/maps/place/W+Albion+Ave+%26+N+Ashland+Ave,+Chicago,+IL+60626/@42.0016833,-87.6704428,3a,75y,341.27h,73.45t/data=!3m7!1e1!3m5!1sD3z9-EFxlzGZMUA7Ehu6mA!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DD3z9-EFxlzGZMUA7Ehu6mA%26output%3Dthumbnail%26cb_client%3Dsearch.TACTILE.gps%26thumb%3D2%26w%3D86%26h%3D86%26yaw%3D358.1608%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656!4m5!3m4!1s0x880fd1bba7352b9b:0x71cc4af7019040dd!8m2!3d42.0017289!4d-87.6705046

I treat that as a roundabout and think it's reasonable to do so.  The main problem with turning left in front of the little island is that there isn't sufficient space for two-way traffic.
Title: Re: Over 6000 roundabouts in America
Post by: vdeane on February 08, 2019, 12:48:09 PM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.
not exactly, but close: NY85 - divided 4-lane 55 MPH, 3 roundabouts within 1 mile stretch.
https://www.google.com/maps/@42.6444845,-73.8563279,1384m/data=!3m1!1e3

45 actually, though NY 85 east of the bypass and NY 140 south/west of it are both 55.  This was actually planned as part of a larger freeway to NY 85A near Voorheesville way back when.  The ROW on the eastern end of the bypass and Krumkill Road has space for the other carriageway.
Title: Re: Over 6000 roundabouts in America
Post by: Rothman on February 08, 2019, 12:52:51 PM
Meh.  NY 85 SB after becoming two lanes to cross the Thruway is not a freeway.
Title: Re: Over 6000 roundabouts in America
Post by: Flint1979 on February 08, 2019, 12:56:56 PM
I never understand what is so difficult about using them. There are several in Michigan and aren't hard to use at all. It's rather simple btw. The traffic in the circle has the right away, there are yield signs at all entries to the circle. It's much better than having traffic lights.
Title: Re: Over 6000 roundabouts in America
Post by: vdeane on February 08, 2019, 01:16:36 PM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.
NY 590 also comes close at Titus Avenue, though there's an at-grade RIRO just to the south.  NB 8 in Fredericton (https://www.google.com/maps/@45.9416102,-66.6714369,17.25z) is probably the true example.
Title: Re: Over 6000 roundabouts in America
Post by: silverback1065 on February 08, 2019, 01:23:12 PM
Carmel when it's all said and done will have around 127.  And a total of around 6 signals in the entire city, only 2 of which will be city signals, the rest will be INDOTs.  Interesting is that one of the first signals in the US and in Indiana was in Carmel at main and rangeline, that one will stay a signal. 
Title: Re: Over 6000 roundabouts in America
Post by: kalvado on February 08, 2019, 01:41:58 PM
I never understand what is so difficult about using them. There are several in Michigan and aren't hard to use at all. It's rather simple btw. The traffic in the circle has the right away, there are yield signs at all entries to the circle. It's much better than having traffic lights.
Several in the state? Oh, man.... How about several in your everyday drive, say driving through 3-4-6 within 1-2 miles? That is when you really get the taste.
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 08, 2019, 02:06:49 PM
I'm talking about something like this: https://www.google.com/maps/place/W+Albion+Ave+%26+N+Ashland+Ave,+Chicago,+IL+60626/@42.0016833,-87.6704428,3a,75y,341.27h,73.45t/data=!3m7!1e1!3m5!1sD3z9-EFxlzGZMUA7Ehu6mA!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DD3z9-EFxlzGZMUA7Ehu6mA%26output%3Dthumbnail%26cb_client%3Dsearch.TACTILE.gps%26thumb%3D2%26w%3D86%26h%3D86%26yaw%3D358.1608%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656!4m5!3m4!1s0x880fd1bba7352b9b:0x71cc4af7019040dd!8m2!3d42.0017289!4d-87.6705046

I treat that as a roundabout and think it's reasonable to do so.  The main problem with turning left in front of the little island is that there isn't sufficient space for two-way traffic.

Meh...  I wouldn't fault anyone for turning in front of the island there.  It's just an all-way stop with a big impediment in the middle.  If I were driving, I would turn in front of it if doing so wouldn't impede any other traffic, but I'd probably treat it as a roundabout if any other cars were nearby.



Oh where should I start...

- Flagrant illegal parking
- Flagrant red light and stop sign running, despite the District having red light cameras.
- Flagrant speed.  While I'll agree that the DC area freeways could stand to have their 55 (or in the District's case, 45 or 50) limits reviewed, far too many drivers consider city streets their personal dragstrip and will rush upwards of 50 in a 25-or-30 in order to "beat the light".

Much more prevalent on the DC/MD side of the Potomac than on the Virginia side, though there are plenty of hotheads in Northern Virginia as well.

Meh...  That just sounds like a healthy disregard for authority to me.  A true dickhead would be the guy who chases down the speeder or red light runner and tries to run him off the road.
Title: Re: Over 6000 roundabouts in America
Post by: jakeroot on February 08, 2019, 02:32:43 PM
Oh where should I start...

- Flagrant illegal parking
- Flagrant red light and stop sign running, despite the District having red light cameras.
- Flagrant speed.  While I'll agree that the DC area freeways could stand to have their 55 (or in the District's case, 45 or 50) limits reviewed, far too many drivers consider city streets their personal dragstrip and will rush upwards of 50 in a 25-or-30 in order to "beat the light".

Much more prevalent on the DC/MD side of the Potomac than on the Virginia side, though there are plenty of hotheads in Northern Virginia as well.

Meh...  That just sounds like a healthy disregard for authority to me.  A true dickhead would be the guy who chases down the speeder or red light runner and tries to run him off the road.

I would agree. I would only consider someone to be a dickhead if they were actively bothering me. Somebody who jumps through a light one-second-too-late, parks in an active lane of traffic, or drives well over the limit isn't cool, but both seem like a hallmark of city driving to me. I see all three in Seattle too, yet Seattle never makes the list of aggressive-driving cities.

Of course, if those things bother you, I can see why you might not like driving in cities. I, on the other hand, relish city driving, as I can screw up without anyone noticing (well, apart from the occasional horn, but no one's trying to kill me).
Title: Re: Over 6000 roundabouts in America
Post by: abefroman329 on February 08, 2019, 02:40:32 PM
I really found driving in DC to be worse than Chicago, maybe even NYC (though I rarely drove in Manhattan and it was never during rush hour).  The only annoying thing in Chicago is people who assume a two-way stop is a four-way stop and cut in front of me when I'm traveling on the street that doesn't actually have a stop sign.
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 08, 2019, 02:44:01 PM
The only annoying thing in Chicago is people who assume a two-way stop is a four-way stop and cut in front of me when I'm traveling on the street that doesn't actually have a stop sign.

There's a general driving mentality in Chicago that, if you don't go now, you won't get to go ever.  I think it might stem from the dearth of left-turn arrows in the city.
Title: Re: Over 6000 roundabouts in America
Post by: abefroman329 on February 08, 2019, 02:49:38 PM
The only annoying thing in Chicago is people who assume a two-way stop is a four-way stop and cut in front of me when I'm traveling on the street that doesn't actually have a stop sign.

There's a general driving mentality in Chicago that, if you don't go now, you won't get to go ever.  I think it might stem from the dearth of left-turn arrows in the city.
If you make a left turn at a signaled intersection without arrows the way you're supposed to, you will get to go, just not right now.
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 08, 2019, 02:58:11 PM
If you make a left turn at a signaled intersection without arrows the way you're supposed to, you will get to go, just not right now.

My experience is that, in heavy traffic, only one person would get to go, maybe two.  Once opposing traffic gets a red light, there's always that one car that will cruise on through after the change to red.  By the time the one or two cars out past the stop line get to clear the intersection, cross-traffic already has the green.  For this reason, I've seen a lot of drivers either (a) turn left the split-second the light turns green in front of oncoming traffic still coming off the line, or else (b) form a chain of five cars turning left after the light has turned red and making cross-traffic just wait there for four seconds of their green time.
Title: Re: Over 6000 roundabouts in America
Post by: abefroman329 on February 08, 2019, 03:07:18 PM
My experience is that, in heavy traffic, only one person would get to go, maybe two.
Right.  So wait you turn.  And tell the relevant elected official that there's regular heavy traffic at that intersection and it needs an arrow for left turns.
Title: Re: Over 6000 roundabouts in America
Post by: NoGoodNamesAvailable on February 08, 2019, 03:22:19 PM


Come to Chicago, where they installed roundabouts as traffic-calming measures on certain streets, but didn't provide any signage on how to use them, and consequently, many drivers make a left-hand turn by turning left at the roundabout.

Actual roundabouts, or just little bitty islands in the middle of the intersections?

Tiny islands. 110th and Talman, for example. (https://www.google.com/maps/@41.6935593,-87.6872312,3a,75y,268.93h,90t/data=!3m6!1e1!3m4!1sUhTgeIPHvsNIpSD7HdXbPg!2e0!7i13312!8i6656?hl=en)

Well, assuming that's the type abefroman329 had in mind, then I don't see what's wrong with turning left in front of the little island.  I probably would.  The intersection you linked to, in fact, has stop signs on two approaches—just like a normal intersection.  That's not a roundabout, so why would people be expected to treat it like one?
I'm talking about something like this: https://www.google.com/maps/place/W+Albion+Ave+%26+N+Ashland+Ave,+Chicago,+IL+60626/@42.0016833,-87.6704428,3a,75y,341.27h,73.45t/data=!3m7!1e1!3m5!1sD3z9-EFxlzGZMUA7Ehu6mA!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DD3z9-EFxlzGZMUA7Ehu6mA%26output%3Dthumbnail%26cb_client%3Dsearch.TACTILE.gps%26thumb%3D2%26w%3D86%26h%3D86%26yaw%3D358.1608%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656!4m5!3m4!1s0x880fd1bba7352b9b:0x71cc4af7019040dd!8m2!3d42.0017289!4d-87.6705046

I treat that as a roundabout and think it's reasonable to do so.  The main problem with turning left in front of the little island is that there isn't sufficient space for two-way traffic.

In the UK and some other countries, turning "offside to offside" is allowed by the road rules and is actually encouraged since it gives you a better view of oncoming traffic. If a queue forms behind a vehicle turning offside to offside, it's expected to leave enough of a gap for the oncoming vehicle to turn through. I wish we were allowed to do this in the US too, but I should know better than to trust drivers in the US to use good judgement rather than just force them to use a single method for uniformity.

(image depicts left-hand traffic)
(https://i.imgur.com/pTBGTLK.png)

So I would definitely agree with going around the island since it's safer, and even if it's illegal I don't think it would confuse other road users.
Title: Re: Over 6000 roundabouts in America
Post by: johndoe on February 08, 2019, 03:35:21 PM
I'm guessing that list came from this site: http://roundabout.kittelson.com/

It's cool to see them on a map.  You can also submit the locations that haven't been added yet.  (as far as I know all of them on there are just submitted by individuals, so certain areas may be more scrutinized than others)
Title: Re: Over 6000 roundabouts in America
Post by: jakeroot on February 08, 2019, 03:45:01 PM
My experience is that, in heavy traffic, only one person would get to go, maybe two.  Once opposing traffic gets a red light, there's always that one car that will cruise on through after the change to red.  By the time the one or two cars out past the stop line get to clear the intersection, cross-traffic already has the green.  For this reason, I've seen a lot of drivers either (a) turn left the split-second the light turns green in front of oncoming traffic still coming off the line, or else (b) form a chain of five cars turning left after the light has turned red and making cross-traffic just wait there for four seconds of their green time.

I've never seen A occur around here before (2-second all-reds make it hard to do), but B is quite common. Though as evidenced in loads of street view images (mostly from Vancouver), two or three cars is the typical 'past the stop line' number of cars (usually only one here in Seattle). Two is most common (http://bit.ly/2E1cra0).

Though if it does happen, A is yet another reason not to wait just past the stop line. Pull as far forward as you physically can without getting in the way. After that last car clears, hopefully a good portion of your turn has already occurred, keeping waiting drivers on the side-street from cutting you off. It's particularly important to do so at intersections without left turn lanes, but with wide medians, which are common in Vancouver (http://bit.ly/2RPNZfB).
Title: Re: Over 6000 roundabouts in America
Post by: jakeroot on February 08, 2019, 03:47:58 PM


Come to Chicago, where they installed roundabouts as traffic-calming measures on certain streets, but didn't provide any signage on how to use them, and consequently, many drivers make a left-hand turn by turning left at the roundabout.

Actual roundabouts, or just little bitty islands in the middle of the intersections?

Tiny islands. 110th and Talman, for example. (https://www.google.com/maps/@41.6935593,-87.6872312,3a,75y,268.93h,90t/data=!3m6!1e1!3m4!1sUhTgeIPHvsNIpSD7HdXbPg!2e0!7i13312!8i6656?hl=en)

Well, assuming that's the type abefroman329 had in mind, then I don't see what's wrong with turning left in front of the little island.  I probably would.  The intersection you linked to, in fact, has stop signs on two approaches—just like a normal intersection.  That's not a roundabout, so why would people be expected to treat it like one?
I'm talking about something like this: https://www.google.com/maps/place/W+Albion+Ave+%26+N+Ashland+Ave,+Chicago,+IL+60626/@42.0016833,-87.6704428,3a,75y,341.27h,73.45t/data=!3m7!1e1!3m5!1sD3z9-EFxlzGZMUA7Ehu6mA!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DD3z9-EFxlzGZMUA7Ehu6mA%26output%3Dthumbnail%26cb_client%3Dsearch.TACTILE.gps%26thumb%3D2%26w%3D86%26h%3D86%26yaw%3D358.1608%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656!4m5!3m4!1s0x880fd1bba7352b9b:0x71cc4af7019040dd!8m2!3d42.0017289!4d-87.6705046

I treat that as a roundabout and think it's reasonable to do so.  The main problem with turning left in front of the little island is that there isn't sufficient space for two-way traffic.

In the UK and some other countries, turning "offside to offside" is allowed by the road rules and is actually encouraged since it gives you a better view of oncoming traffic. If a queue forms behind a vehicle turning offside to offside, it's expected to leave enough of a gap for the oncoming vehicle to turn through. I wish we were allowed to do this in the US too, but I should know better than to trust drivers in the US to use good judgement rather than just force them to use a single method for uniformity.

(image depicts left-hand traffic)
https://i.imgur.com/pTBGTLK.png

So I would definitely agree with going around the island since it's safer, and even if it's illegal I don't think it would confuse other road users.

Offside turning is the norm at a few wide intersections in Vancouver. I filmed myself going through one a long time ago (skip to around 2:00):

Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 08, 2019, 03:56:17 PM

My experience is that, in heavy traffic, only one person would get to go, maybe two.

Right.  So wait you turn.  And tell the relevant elected official that there's regular heavy traffic at that intersection and it needs an arrow for left turns.

I prefer actually getting to where I'm going and, from what I've seen, a lot of other people prefer that too.




(a) turn left the split-second the light turns green in front of oncoming traffic still coming off the line

I've never seen A occur around here before (2-second all-reds make it hard to do)

I'm not sure if you're understanding me correctly or not.

1.  You're waiting to turn left.
2.  The light turns red, but only the car in front of you has time to turn left.
3.  You're now at the front of the line in the left-turn lane (if there is one).
4.  Cross-traffic gets the green and does their thing.
5.  Cross-traffic gets a red light.
6.  A few stragglers finish up their turns during the all-red phase.
7.  Your light and that for oncoming traffic gets the green.
8.  While oncoming traffic is still getting in gear, you immediately turn left in front of them.

The duration of the all-red phase doesn't really have much effect on one's ability to do this sort of thing.
Title: Re: Over 6000 roundabouts in America
Post by: Rothman on February 08, 2019, 04:02:19 PM
Turning left at the green in front of opposing traffic was commonplace in MA when I was a kid, but the practice seems to be lessening.
Title: Re: Over 6000 roundabouts in America
Post by: US 89 on February 08, 2019, 04:20:11 PM
Turning left at the green in front of opposing traffic was commonplace in MA when I was a kid, but the practice seems to be lessening.

Such is apparently called a Pittsburgh left (https://en.wikipedia.org/wiki/Pittsburgh_left). In my experience (largely in the West and South) I've seen it done on a few occasions, but almost always it just seems rude.
Title: Re: Over 6000 roundabouts in America
Post by: jakeroot on February 08, 2019, 04:37:14 PM
(a) turn left the split-second the light turns green in front of oncoming traffic still coming off the line

I've never seen A occur around here before (2-second all-reds make it hard to do)

I'm not sure if you're understanding me correctly or not.

1.  You're waiting to turn left.
2.  The light turns red, but only the car in front of you has time to turn left.
3.  You're now at the front of the line in the left-turn lane (if there is one).
4.  Cross-traffic gets the green and does their thing.
5.  Cross-traffic gets a red light.
6.  A few stragglers finish up their turns during the all-red phase.
7.  Your light and that for oncoming traffic gets the green.
8.  While oncoming traffic is still getting in gear, you immediately turn left in front of them.

The duration of the all-red phase doesn't really have much effect on one's ability to do this sort of thing.

You're right, I misunderstood. My bad. I thought you were referring to traffic from the cross-street setting off the line so quickly as to cut off cars still waiting to turn left. Which seems so odd to me, but knowing Chicago drivers, it seems like a plausible move.

I never see the Pittsburgh left around here, except at intersections that meet around the 45-degree mark. The sharper of the left turns can sometimes be made so quickly, you can do it before oncoming cars reach you.
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 08, 2019, 04:45:12 PM
I thought you were referring to traffic from the cross-street setting off the line so quickly as to cut off cars still waiting to turn left. Which seems so odd to me, but knowing Chicago drivers, it seems like a plausible move.

Oh gosh, no!  Not waiting for left-turn stragglers would get you killed in Chicago.  That's a T-bone wreck just waiting to happen.  This is especially true because those left-turn stragglers are some of the fastest cars through the intersection and there's no turning back once they've committed.
Title: Re: Over 6000 roundabouts in America
Post by: Flint1979 on February 08, 2019, 04:49:40 PM
I never understand what is so difficult about using them. There are several in Michigan and aren't hard to use at all. It's rather simple btw. The traffic in the circle has the right away, there are yield signs at all entries to the circle. It's much better than having traffic lights.
Several in the state? Oh, man.... How about several in your everyday drive, say driving through 3-4-6 within 1-2 miles? That is when you really get the taste.
Yeah several. I don't have an exact count of how many traffic circles Michigan has but there are a lot of them. There are a lot of them in Oakland County that you'd drive through like that.
Title: Re: Over 6000 roundabouts in America
Post by: BrianP on February 08, 2019, 05:26:37 PM
Turning left at the green in front of opposing traffic was commonplace in MA when I was a kid, but the practice seems to be lessening.

Such is apparently called a Pittsburgh left (https://en.wikipedia.org/wiki/Pittsburgh_left). In my experience (largely in the West and South) I've seen it done on a few occasions, but almost always it just seems rude.
I've seen this happen many times here:
https://www.google.com/maps/@39.1707592,-77.2625327,3a,75y,325.28h,92.69t/data=!3m6!1e1!3m4!1sngd26qr69BlTaPiTR3z0cA!2e0!7i13312!8i6656

I haven't seen it anywhere else.  The only reason I think it happens here is the size of the intersection and the lack of a turn arrow.  But that's not unique.  But for some reason it happens there.  Like someone did it once and it caught on.  But not everyone does it. 
Title: Re: Over 6000 roundabouts in America
Post by: MantyMadTown on February 08, 2019, 05:40:16 PM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.
not exactly, but close: NY85 - divided 4-lane 55 MPH, 3 roundabouts within 1 mile stretch.
https://www.google.com/maps/@42.6444845,-73.8563279,1384m/data=!3m1!1e3

Only 15 mph through the roundabout. Doesn't really feel close.

The closest I can think of to a "freeway roundabout" would be the large high-speed rotaries they have in the Northeast. I don't know specifically where they exist however.
I don't think freeways in the U.S. can legally have roundabouts or rotaries on their mainline. The definition of a freeway here means that it's controlled access, so the only way to get on or off a freeway is through on/off ramps. I could see two expressways having one (in Wisconsin they're defined as limited access).

I'm guessing that list came from this site: http://roundabout.kittelson.com/

It's cool to see them on a map.  You can also submit the locations that haven't been added yet.  (as far as I know all of them on there are just submitted by individuals, so certain areas may be more scrutinized than others)

I just submitted the planned roundabout in my hometown to the site. I don't know if they include ones that haven't been built though.
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 08, 2019, 06:00:42 PM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.

Though obviously not in America, the junction of the M1 and M50 on the north side of Dublin (RoI) was a roundabout with slip lanes until a 2008-2010 project made it free-flow.
Title: Re: Over 6000 roundabouts in America
Post by: bcroadguy on February 09, 2019, 03:44:37 AM
I guess this would kinda count as a freeway roundabout?

https://www.google.com/maps/@46.0974443,-64.7697549,15.72z
Title: Re: Over 6000 roundabouts in America
Post by: jeffandnicole on February 09, 2019, 06:09:25 AM
I can deal with roundabouts; it's the other idiots that can't seem to figure out how to properly yield that make them unpleasant for me. I have to pray that I don't get cut off from when another car approaches when I'm already in the roundabout.

Remember, if you feel that way about others, others are probably thinking the same thing about you as you approach a roundabout!

Ah, I see the warning signs now.

Technically, warning signs don't tell you what to do, just what to watch out for.  I'm struggling to come up with any guidance in the Illinois Vehicle Code on what to do at a roundabout or traffic circle, so it's possible it's actually a legal loophole.

I would think basic intersection protocal would apply (ie: keep right). 

Or, to think about it this way: If you turned left in front of the island, and another car hit you head on, would you think the car on the right (the one you hit) have the right of way, or would you (on the left) have the right of way?  That seemingly makes the answer much clearer.
Title: Re: Over 6000 roundabouts in America
Post by: tradephoric on February 09, 2019, 01:29:21 PM
I'm guessing that list came from this site: http://roundabout.kittelson.com/

It's cool to see them on a map.  You can also submit the locations that haven't been added yet.  (as far as I know all of them on there are just submitted by individuals, so certain areas may be more scrutinized than others)

That KML file i posted was created independently from that kittelson website.  Thank you for posting that link as i had never seen the kittelson database before.  It looks like a tremendous resource.  Within 10 minutes of looking through that website, i found dozens of examples of modern roundabouts that were not included in my database and vice versa.
Title: Re: Over 6000 roundabouts in America
Post by: tradephoric on February 09, 2019, 01:33:46 PM
^By the way, it looks like you can export the entire kittelson database into one large KML file if you click on INDEX and then the blue button that says "export as KML".  From there you can compare both databases together to see which roundabouts are potentially missing from each.
Title: Re: Over 6000 roundabouts in America
Post by: vdeane on February 09, 2019, 05:27:04 PM
I guess this would kinda count as a freeway roundabout?

https://www.google.com/maps/@46.0974443,-64.7697549,15.72z
Assuming one counts NB 15 there as a freeway.  Note the traffic light.

I already posted the other (much smaller) NB example in Fredericton.
Title: Re: Over 6000 roundabouts in America
Post by: MantyMadTown on February 10, 2019, 01:42:33 AM
I guess this would kinda count as a freeway roundabout?

https://www.google.com/maps/@46.0974443,-64.7697549,15.72z

That's a pretty big roundabout. Using the scale on Google Maps it looks like it has a diameter of roughly 1000 ft. It looks as big as the shopping mall right next to it. I wouldn't want to build such a big roundabout in the middle of any city.
Title: Re: Over 6000 roundabouts in America
Post by: bcroadguy on February 10, 2019, 04:58:57 AM
I guess this would kinda count as a freeway roundabout?

https://www.google.com/maps/@46.0974443,-64.7697549,15.72z
Assuming one counts NB 15 there as a freeway.  Note the traffic light.

I already posted the other (much smaller) NB example in Fredericton.

I just saw all the interchanges near it on Google Maps and kinda assumed it was a freeway for the most part / didn't notice the traffic light. Oops.

I saw the Fredericton example, but I thought I'd post this just because it's pretty big / relatively high speed for a roundabout (60 km/h limit inside the roundabout).
Title: Re: Over 6000 roundabouts in America
Post by: bcroadguy on February 10, 2019, 05:09:45 AM
I guess this would kinda count as a freeway roundabout?

https://www.google.com/maps/@46.0974443,-64.7697549,15.72z

That's a pretty big roundabout. Using the scale on Google Maps it looks like it has a diameter of roughly 1000 ft. It looks as big as the shopping mall right next to it. I wouldn't want to build such a big roundabout in the middle of any city.

And for such a huge roundabout, it seems pretty useless too. Judging from Google Maps, it looks like they could just get rid of it entirely and make all the traffic that exits there take the Paul St. interchange immediately east of it.

Edit: Didn't realize it wasn't a full movement diamond interchange, but they could easily convert it to one by adding signals on Paul St. / allowing left turns onto Paul St.
Title: Re: Over 6000 roundabouts in America
Post by: jakeroot on February 10, 2019, 05:14:12 PM
I guess this would kinda count as a freeway roundabout?

https://www.google.com/maps/@46.0974443,-64.7697549,15.72z

That's a pretty big roundabout. Using the scale on Google Maps it looks like it has a diameter of roughly 1000 ft. It looks as big as the shopping mall right next to it. I wouldn't want to build such a big roundabout in the middle of any city.

And for such a huge roundabout, it seems pretty useless too. Judging from Google Maps, it looks like they could just get rid of it entirely and make all the traffic that exits there take the Paul St. interchange immediately east of it.

Edit: Didn't realize it wasn't a full movement diamond interchange, but they could easily convert it to one by adding signals on Paul St. / allowing left turns onto Paul St.

As far as I can tell, the roundabout isn't there to facilitate U-turn movements for Paul Street, but to connect Wheeler Blvd with Route 15.
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 11, 2019, 02:30:23 PM

Ah, I see the warning signs now.

Technically, warning signs don't tell you what to do, just what to watch out for.  I'm struggling to come up with any guidance in the Illinois Vehicle Code on what to do at a roundabout or traffic circle, so it's possible it's actually a legal loophole.

I would think basic intersection protocal would apply (ie: keep right). 

Or, to think about it this way: If you turned left in front of the island, and another car hit you head on, would you think the car on the right (the one you hit) have the right of way, or would you (on the left) have the right of way?  That seemingly makes the answer much clearer.

"Keep right" laws often have an exclusion for turning left and/or for obstructions in the roadway, but it doesn't matter anyway because I found the state law for roundabouts and traffic circles.

Quote from: 625 ILCS 5, Sec. 11-708 (c)
A vehicle passing around a rotary traffic island must be driven only to the right of such island.
Title: Re: Over 6000 roundabouts in America
Post by: ScottRAB on February 11, 2019, 03:49:33 PM
I guess this would kinda count as a freeway roundabout?

https://www.google.com/maps/@46.0974443,-64.7697549,15.72z

Traffic engineers classify circular intersections by diameter and traffic control.  That link would be a traffic circle, or rotary.
Many people confuse other and older styles of circular intersections with modern roundabouts. High speed, east coast rotaries, large multi-lane traffic circles (Arc D’Triomphe, Dupont Circle), and small neighborhood traffic circles are not modern roundabouts and UK 'roundabouts' are not the same as US 'roundabouts'.  The Brits even call a merry-go-round a kid’s roundabout.
What is, and is not, a modern roundabout:
UMass video:

WA DOT: 
NJ traffic circles: https://en.wikipedia.org/wiki/List_of_traffic_circles_in_New_Jersey
NJ wins award for building roundabout:
https://www.prnewswire.com/news-releases/national-roadway-safety-award-winners-announced-300556007.html
Title: Re: Over 6000 roundabouts in America
Post by: ScottRAB on February 11, 2019, 03:50:34 PM
They're all crash-prone.

Modern roundabouts are the safest form of intersection in the world - the intersection type with the lowest risk of fatal or serious injury crashes - (much more so than comparable signals).  Modern roundabouts require a change in speed and alter the geometry of one of the most dangerous parts of the system - intersections. 

The reduction in speed to about 20 mph and sideswipe geometry mean that, when a crash does happen at a modern roundabout, you usually need a tow truck, not an ambulance.  Visit the Insurance Institute for Highway Safety for modern roundabout FAQs and safety facts.  Roundabouts are one of several proven road safety features (FHWA). 
The life saved may be your own.
https://safety.fhwa.dot.gov/provencountermeasures/roundabouts/
https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/
Title: Re: Over 6000 roundabouts in America
Post by: ScottRAB on February 11, 2019, 03:53:38 PM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.
not exactly, but close: NY85 - divided 4-lane 55 MPH, 3 roundabouts within 1 mile stretch.
https://www.google.com/maps/@42.6444845,-73.8563279,1384m/data=!3m1!1e3

The point of a modern roundabout is to reduce to near zero the probability of a fatal crash at an intersection.  High speed is not  a feature of a modern roundabout.  The definitions do matter if you're going to confuse the three primary forms of circular intersection.
Title: Re: Over 6000 roundabouts in America
Post by: abefroman329 on February 11, 2019, 04:00:39 PM
I'm talking about something like this: https://www.google.com/maps/place/W+Albion+Ave+%26+N+Ashland+Ave,+Chicago,+IL+60626/@42.0016833,-87.6704428,3a,75y,341.27h,73.45t/data=!3m7!1e1!3m5!1sD3z9-EFxlzGZMUA7Ehu6mA!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DD3z9-EFxlzGZMUA7Ehu6mA%26output%3Dthumbnail%26cb_client%3Dsearch.TACTILE.gps%26thumb%3D2%26w%3D86%26h%3D86%26yaw%3D358.1608%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656!4m5!3m4!1s0x880fd1bba7352b9b:0x71cc4af7019040dd!8m2!3d42.0017289!4d-87.6705046

I treat that as a roundabout and think it's reasonable to do so.  The main problem with turning left in front of the little island is that there isn't sufficient space for two-way traffic.

Meh...  I wouldn't fault anyone for turning in front of the island there.  It's just an all-way stop with a big impediment in the middle.  If I were driving, I would turn in front of it if doing so wouldn't impede any other traffic, but I'd probably treat it as a roundabout if any other cars were nearby.
It's now officially signed as a roundabout, so...I was right all along.
Title: Re: Over 6000 roundabouts in America
Post by: MNHighwayMan on February 11, 2019, 04:05:07 PM
They're all crash-prone.
Modern roundabouts are the safest form of intersection in the world - the intersection type with the lowest risk of fatal or serious injury crashes - (much more so than comparable signals).  Modern roundabouts require a change in speed and alter the geometry of one of the most dangerous parts of the system - intersections. 

The reduction in speed to about 20 mph and sideswipe geometry mean that, when a crash does happen at a modern roundabout, you usually need a tow truck, not an ambulance.  Visit the Insurance Institute for Highway Safety for modern roundabout FAQs and safety facts.  Roundabouts are one of several proven road safety features (FHWA). 
The life saved may be your own.
https://safety.fhwa.dot.gov/provencountermeasures/roundabouts/
https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/

Oh man, you have no idea. (https://www.aaroads.com/forum/index.php?topic=15546.0)
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 11, 2019, 04:38:03 PM

They're all crash-prone.

Modern roundabouts are the safest form of intersection in the world - the intersection type with the lowest risk of fatal or serious injury crashes - (much more so than comparable signals).  Modern roundabouts require a change in speed and alter the geometry of one of the most dangerous parts of the system - intersections. 

The reduction in speed to about 20 mph and sideswipe geometry mean that, when a crash does happen at a modern roundabout, you usually need a tow truck, not an ambulance.  Visit the Insurance Institute for Highway Safety for modern roundabout FAQs and safety facts.  Roundabouts are one of several proven road safety features (FHWA). 
The life saved may be your own.
https://safety.fhwa.dot.gov/provencountermeasures/roundabouts/
https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/

You're new here, and I was being sarcastic.  Please do take a look at the thread MNHighwwayMan linked to.  Do so when you have a good hour or two to read through a lot of the thread.  tradephoric, through all the noise of his rhetoric, does put forward good evidence that there is a great deal of variance in safety between simple single-lane roundabouts and larger multi-lane roundabouts.  State DOTs are only recently beginning, it seems, to get an inkling of this variance.
Title: Re: Over 6000 roundabouts in America
Post by: jakeroot on February 11, 2019, 05:41:49 PM
Guys, he's already posted in that thread on several occasions. He seems to have FritzOwl levels of defiance, repeating the same rhetoric over, and over, and over again (using very nearly the same wording too). Note this post (https://www.aaroads.com/forum/index.php?topic=15546.msg2361036#msg2361036) by him in that thread from last October. The data is before him, but judging by his username including "RAB", he's probably already made up his mind what he thinks.
Title: Re: Over 6000 roundabouts in America
Post by: kalvado on February 11, 2019, 05:51:22 PM
Guys, he's already posted in that thread on several occasions. He seems to have FritzOwl levels of defiance, repeating the same rhetoric over, and over, and over again (using very nearly the same wording too). Note this post (https://www.aaroads.com/forum/index.php?topic=15546.msg2361036#msg2361036) by him in that thread from last October. The data is before him, but judging by his username including "RAB", he's probably already made up his mind what he thinks.
What is RAB?
Title: Re: Over 6000 roundabouts in America
Post by: jakeroot on February 11, 2019, 06:05:24 PM
Guys, he's already posted in that thread on several occasions. He seems to have FritzOwl levels of defiance, repeating the same rhetoric over, and over, and over again (using very nearly the same wording too). Note this post (https://www.aaroads.com/forum/index.php?topic=15546.msg2361036#msg2361036) by him in that thread from last October. The data is before him, but judging by his username including "RAB", he's probably already made up his mind what he thinks.
What is RAB?

RoundABout
Title: Re: Over 6000 roundabouts in America
Post by: skluth on February 11, 2019, 06:28:05 PM
I guess this would kinda count as a freeway roundabout?

https://www.google.com/maps/@46.0974443,-64.7697549,15.72z

That's a pretty big roundabout. Using the scale on Google Maps it looks like it has a diameter of roughly 1000 ft. It looks as big as the shopping mall right next to it. I wouldn't want to build such a big roundabout in the middle of any city.

It's in a flood plain. Those wetlands probably help reduce flooding nearby, even though there's practically no elevation difference between the wetlands and the mall.
Title: Re: Over 6000 roundabouts in America
Post by: tradephoric on February 11, 2019, 06:50:22 PM
ScottRAB, here's a roundabout video the IIHS put together talking about the safety of roundabouts.  You should link to this video when you are out shilling...

Title: Re: Over 6000 roundabouts in America
Post by: MantyMadTown on February 12, 2019, 01:32:21 AM
ScottRAB, here's a roundabout video the IIHS put together talking about the safety of roundabouts.  You should link to this video when you are out shilling...


Man, these people don't know how to use roundabouts. Jumping over them and trying to pass through at high speeds, that's like the most blatantly wrong thing you can do at a roundabout. They're pretty safe if you use them correctly.
Title: Re: Over 6000 roundabouts in America
Post by: Plutonic Panda on February 12, 2019, 01:47:43 AM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.
Let's please not make this a thing. Completely defeats the purpose of a "freeway"!
Title: Re: Over 6000 roundabouts in America
Post by: tradephoric on February 12, 2019, 07:55:29 AM
Modern roundabouts are the safest form of intersection in the world - the intersection type with the lowest risk of fatal or serious injury crashes - (much more so than comparable signals).  Modern roundabouts require a change in speed and alter the geometry of one of the most dangerous parts of the system - intersections. 

A 2017 roundabout study out of Minnesota found that the dual lane roundabouts saw a 6% increase in injury crashes and a 212.5% increase in PDO crashes.   If we use FHWA’s comprehensive crash costs by injury severity level to perform a cost/benefit analysis, we see that these dual-lane Minnesota roundabouts increased crash costs by $1,664,300 over the comparable intersections they replaced.  Even though there were 3 less A-level crashes at the roundabouts, there were 7 more C-level crashes and a whopping 270 more PDO crashes.

(https://i.imgur.com/D77VC6z.png)
http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

BEFORE ROUNDABOUT CRASH COSTS = $4,882,600
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   3 X  $216,000 = $648,000
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   46 X $44,900 = $2,065,400
PDO (O)          133 X $7,400 =  $984,200

AFTER ROUNDABOUT CRASH COSTS = $6,546,900
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   0 X  $216,000 = $0
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   53 X $44,900 = $2,379,700
PDO (O)          403 X $7,400 =  $2,982,200

Instead of constructing complex multi-lane roundabouts that are prone to crashes (and increases in injury crashes) maybe agencies should consider innovative signal designs that eliminate direct left turns.  Median U-turns have been implemented in Michigan for over 50 years and have proven safety benefits with the FHWA estimating that they reduce injury crashes by 30% https://safety.fhwa.dot.gov/intersection/alter_design/pdf/fhwasa14069_mut_infoguide.pdf.  A 30% decrease in injury crashes sounds pretty good compared to a 6% increase in injuries these complex roundabouts are seeing.
Title: Re: Over 6000 roundabouts in America
Post by: 1 on February 12, 2019, 08:03:04 AM
Sometimes, it's hard to tell a roundabout/rotary/traffic circle from a median U-turn. See US 1 at I-95 in Danvers, MA.
Title: Re: Over 6000 roundabouts in America
Post by: tradephoric on February 12, 2019, 08:24:45 AM
Sometimes, it's hard to tell a roundabout/rotary/traffic circle from a median U-turn. See US 1 at I-95 in Danvers, MA.

That interchange really does start to mirror a median U-turn.  Here's a synchro model that is very similar to that US 1 at I-95 interchange just the off-ramp are signalized instead of free-flowing.  I like the concept.

Title: Re: Over 6000 roundabouts in America
Post by: kalvado on February 12, 2019, 08:40:44 AM
Sometimes, it's hard to tell a roundabout/rotary/traffic circle from a median U-turn. See US 1 at I-95 in Danvers, MA.
Topological similarity, maybe, but not conceptual similarity, I would say. Need to change lanes, much larger scale compared to a typical roundabout.
But overall, there are often examples where extreme cases are clearly different, but there are some intermediates which are neither one nor the other.  My pet example for today is viruses, which are neither alive nor truly dead - but somewhere in between, achoo....
Title: Re: Over 6000 roundabouts in America
Post by: NE2 on February 12, 2019, 01:08:58 PM
freeway roundabout (https://www.google.com/maps/@41.943402,-74.0276808,3a,75y,304.79h,91.88t/data=!3m6!1e1!3m4!1sv2ICaZu3MPltKubZJSo1dQ!2e0!7i13312!8i6656)
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 12, 2019, 01:12:50 PM
You keep viruses as pets?
Title: Re: Over 6000 roundabouts in America
Post by: kphoger on February 12, 2019, 01:13:52 PM
freeway roundabout (https://www.google.com/maps/@41.943402,-74.0276808,3a,75y,304.79h,91.88t/data=!3m6!1e1!3m4!1sv2ICaZu3MPltKubZJSo1dQ!2e0!7i13312!8i6656)

mmmm,,,   .......   barely.... ?
Title: Re: Over 6000 roundabouts in America
Post by: kalvado on February 12, 2019, 01:19:27 PM
You keep viruses as pets?
Hopefully just for a few days at most.
Title: Re: Over 6000 roundabouts in America
Post by: NE2 on February 12, 2019, 02:01:54 PM
More freeway roundabouts:
Fredericton NB: https://www.google.com/maps/@45.9397918,-66.666871,3a,75y,315.88h,86.34t/data=!3m6!1e1!3m4!1sHs8rcLur-7Odtd1RF0HMsQ!2e0!7i13312!8i6656
Pictou NS: https://www.google.com/maps/@45.6858615,-62.728353,3a,29.8y,209.16h,87.95t/data=!3m6!1e1!3m4!1stTYvOlCuIIqEuykWjZYCQg!2e0!7i13312!8i6656
Title: Re: Over 6000 roundabouts in America
Post by: skluth on February 12, 2019, 02:36:19 PM
Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.

This triple-lane roundabout in Wisconsin replaced a trumpet interchange about 10 years ago:

https://www.google.com/maps/@44.9210291,-91.3805333,156m/data=!3m1!1e3

I wouldn't be surprised if WIDoT is thinking about one somewhere right now.
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 12, 2019, 02:56:18 PM
I'm guessing that list came from this site: http://roundabout.kittelson.com/

It's cool to see them on a map.  You can also submit the locations that haven't been added yet.  (as far as I know all of them on there are just submitted by individuals, so certain areas may be more scrutinized than others)

I updated the roundabout database and changed the title to "Over 7000 roundabouts in America".  The kittelson website had a bunch of modern roundabouts that weren't included in my database.  The difference between my database and kittelson is that mine mainly focuses on modern roundabouts while they include traffic circles, rotaries, roundabouts, traffic calming circles, and mini roundabouts. I even stumbled upon a few culdesac circles in their database. 

Here is my database with about 7000 modern roundabouts:
http://www.mediafire.com/file/j6zcvi91whg3j2u/Roundabouts+%282019-02-12%29.kmz
Title: Re: Over 7000 roundabouts in America
Post by: kphoger on February 12, 2019, 03:03:01 PM
Fredericton NB: https://www.google.com/maps/@45.9397918,-66.666871,3a,75y,315.88h,86.34t/data=!3m6!1e1!3m4!1sHs8rcLur-7Odtd1RF0HMsQ!2e0!7i13312!8i6656

That's a great example!



This triple-lane roundabout in Wisconsin replaced a trumpet interchange about 10 years ago:

https://www.google.com/maps/@44.9210291,-91.3805333,156m/data=!3m1!1e3

I don't think it's fair to call something a "triple-lane roundabout" when...
 (a) all approach roads are two lanes,
 (b) the circulating roadway is two lanes.

There's only the briefest segment that has three lanes inside the actual roundabout.
Title: Re: Over 7000 roundabouts in America
Post by: MNHighwayMan on February 12, 2019, 03:17:49 PM
I don't think it's fair to call something a "triple-lane roundabout" when...
 (a) all approach roads are two lanes,
 (b) the circulating roadway is two lanes.

There's only the briefest segment that has three lanes inside the actual roundabout.

It's a 2¼ lane roundabout then. :)
Title: Re: Over 6000 roundabouts in America
Post by: skluth on February 12, 2019, 03:20:14 PM
More freeway roundabouts:
Fredericton NB: https://www.google.com/maps/@45.9397918,-66.666871,3a,75y,315.88h,86.34t/data=!3m6!1e1!3m4!1sHs8rcLur-7Odtd1RF0HMsQ!2e0!7i13312!8i6656
Pictou NS: https://www.google.com/maps/@45.6858615,-62.728353,3a,29.8y,209.16h,87.95t/data=!3m6!1e1!3m4!1stTYvOlCuIIqEuykWjZYCQg!2e0!7i13312!8i6656

I wouldn't consider the Pictou example as a freeway roundabout as it's not a freeway. NS 106 is two lanes. It may be limited access, but that doesn't make it a freeway.
Title: Re: Over 7000 roundabouts in America
Post by: kphoger on February 12, 2019, 03:27:17 PM

More freeway roundabouts:
Fredericton NB: https://www.google.com/maps/@45.9397918,-66.666871,3a,75y,315.88h,86.34t/data=!3m6!1e1!3m4!1sHs8rcLur-7Odtd1RF0HMsQ!2e0!7i13312!8i6656
Pictou NS: https://www.google.com/maps/@45.6858615,-62.728353,3a,29.8y,209.16h,87.95t/data=!3m6!1e1!3m4!1stTYvOlCuIIqEuykWjZYCQg!2e0!7i13312!8i6656

I wouldn't consider the Pictou example as a freeway roundabout as it's not a freeway. NS 106 is two lanes. It may be limited access, but that doesn't make it a freeway.

Looks like a freeway to me.  The number of lanes is rather irrelevant:  controlled access, no cross-traffic.  The only thing is that it might be short enough that the whole highway segment could be discounted as a freeway simply because the roundabout exists.
Title: Re: Over 7000 roundabouts in America
Post by: formulanone on February 12, 2019, 05:48:25 PM
ScottRAB, here's a roundabout video the IIHS put together talking about the safety of roundabouts.  You should link to this video when you are out shilling...


You posted a video posting every idiotic maneuver by inattentiveness or being flat-out dangerous, but surely it's the roundabout's fault.

You must be a traffic light sales-hole.
Title: Re: Over 7000 roundabouts in America
Post by: Max Rockatansky on February 12, 2019, 05:55:59 PM
Saw the title of the thread changed numbers, let me know when it’s over 9,000. 
Title: Re: Over 7000 roundabouts in America
Post by: jakeroot on February 12, 2019, 06:52:41 PM
You posted a video posting every idiotic maneuver by inattentiveness or being flat-out dangerous, but surely it's the roundabout's fault.

You must be a traffic light sales-hole.

He's simply highlighting the FHWA's ridiculous notion that roundabouts force drivers to do anything: slow down, yield, etc. Those things only happen if drivers choose to do them. Which most people will, yeah. But those that don't... they're gonna have a bad time.

And, before anyone says anything, none of this Darwinism business. Engineers are in the business of saving all lives, even the morons.
Title: Re: Over 7000 roundabouts in America
Post by: vdeane on February 12, 2019, 07:19:25 PM
Fredericton NB: https://www.google.com/maps/@45.9397918,-66.666871,3a,75y,315.88h,86.34t/data=!3m6!1e1!3m4!1sHs8rcLur-7Odtd1RF0HMsQ!2e0!7i13312!8i6656

That's a great example!

*cough*

Are there any freeway roundabouts? I could see this concept work in rural areas with lots of room for a wide radius to keep speed. Would save on overpasses and flyovers.
NY 590 also comes close at Titus Avenue, though there's an at-grade RIRO just to the south.  NB 8 in Fredericton (https://www.google.com/maps/@45.9416102,-66.6714369,17.25z) is probably the true example.
Title: Re: Over 7000 roundabouts in America
Post by: billpa on February 13, 2019, 04:54:16 AM
You posted a video posting every idiotic maneuver by inattentiveness or being flat-out dangerous, but surely it's the roundabout's fault.

You must be a traffic light sales-hole.

He's simply highlighting the FHWA's ridiculous notion that roundabouts force drivers to do anything: slow down, yield, etc. Those things only happen if drivers choose to do them. Which most people will, yeah. But those that don't... they're gonna have a bad time.

And, before anyone says anything, none of this Darwinism business. Engineers are in the business of saving all lives, even the morons.
The problem with the old thread and now, predictably this one, are the videos and stories handpicked to attempt to put roundabouts in a bad light. If someone drives at 60 mph strait through a roundabout the design and theory behind the intersection is not at fault. No one makes an argument that plowing through a red light means traffic light-controlled intersections are inherently dangerous.

Pixel 2

Title: Re: Over 7000 roundabouts in America
Post by: jeffandnicole on February 13, 2019, 06:10:51 AM
ScottRAB, here's a roundabout video the IIHS put together talking about the safety of roundabouts.  You should link to this video when you are out shilling...


I don't see anything that shows the IIHS is responsible for this video.  Someone simply took their logo, stuck it at the front of the video, and found other clips of accidents.  Heck, how does someone passing in a non-passing zone have anything to do with the roundabout?
Title: Re: Over 7000 roundabouts in America
Post by: english si on February 13, 2019, 07:22:15 AM
He's simply highlighting the FHWA's ridiculous notion that roundabouts force drivers to do anything: slow down, yield, etc. Those things only happen if drivers choose to do them.
This is true, but the way they want DOTs to do the geometry, etc does a better and more hands-on job at getting them to obey than mere signs, or lights by making the danger clear and present - rather than unseen and only there sometimes (say if you run a red light when traffic is quiet).

'Force' isn't quite the right word, but what the FHWA is getting at is to 'strongly encourage' people do something with more than just words and potential threat (of a ticket or a smash).

Of course, the engineers don't always get it correct, and the drivers likewise are sometimes unfit to be safe on the road and will come a cropper when they don't obey the strong encouragement to follow the rules of the roundabout when they might survive running through a stop sign or red light.
Title: Re: Over 7000 roundabouts in America
Post by: D-Dey65 on February 13, 2019, 07:46:48 AM
Meh.  NY 85 SB after becoming two lanes to cross the Thruway is not a freeway.
Somehow I think the use of the roundabouts might be a way to get people south of the Thruway to accept four lanes along NY 85, even if it isn't.

OT, I think I see a few makeshift exit ramp parts at some intersections in Voorheesville on GSV at places like Clipp Road and the vicinity of Helderhill Road.


Title: Re: Over 7000 roundabouts in America
Post by: Rothman on February 13, 2019, 08:39:16 AM


Meh.  NY 85 SB after becoming two lanes to cross the Thruway is not a freeway.
Somehow I think the use of the roundabouts might be a way to get people south of the Thruway to accept four lanes along NY 85, even if it isn't.

OT, I think I see a few makeshift exit ramp parts at some intersections in Voorheesville on GSV at places like Clipp Road and the vicinity of Helderhill Road.

The bypass has been a great improvement.  The light at Blessing Road was horrendous and almost seemed unnecessary; the roundabout there has been most welcome.  Getting through the lights on New Scotland was annoying and, although there were quite a number of fender benders due to human error at the get-go, I haven't seen an accident at the NY 85/NY 140 roundabout in a very long time (tradephoric likes to focus on the accident-prone transition period and ignore when accident dropoffs happen at those same sites).

So, I don't know how much the roundabouts were for convincing Bethlehem that four lanes were needed as much as it was built to address the congestion and to allow some commercial development (although I can't imagine that Shop Rite is doing very well from the traffic I see).

The Clipp Road thing is just a private pullout (you can see the property signs on the trees).  Same goes for Helderhill.
Title: Re: Over 7000 roundabouts in America
Post by: kalvado on February 13, 2019, 11:33:59 AM


Meh.  NY 85 SB after becoming two lanes to cross the Thruway is not a freeway.
Somehow I think the use of the roundabouts might be a way to get people south of the Thruway to accept four lanes along NY 85, even if it isn't.

OT, I think I see a few makeshift exit ramp parts at some intersections in Voorheesville on GSV at places like Clipp Road and the vicinity of Helderhill Road.

The bypass has been a great improvement.  The light at Blessing Road was horrendous and almost seemed unnecessary; the roundabout there has been most welcome.  Getting through the lights on New Scotland was annoying and, although there were quite a number of fender benders due to human error at the get-go, I haven't seen an accident at the NY 85/NY 140 roundabout in a very long time (tradephoric likes to focus on the accident-prone transition period and ignore when accident dropoffs happen at those same sites).

So, I don't know how much the roundabouts were for convincing Bethlehem that four lanes were needed as much as it was built to address the congestion and to allow some commercial development (although I can't imagine that Shop Rite is doing very well from the traffic I see).

The Clipp Road thing is just a private pullout (you can see the property signs on the trees).  Same goes for Helderhill.
Bypass was a great improvement in terms of rerouting 85 and not dumping all that traffic on New Scotland.
In terms of development - I believe that SHopRite is still the only larger tenant in Vista Technology Campus.
Roundabouts... well, replacing "no turn on red" woth some merge lanes can also go a long way. And those roundabouts were at the top of crash lists for quite a while. Probably long enough so that total elimination of crashes for next 20 years wouldn't brake it even.
My bet  is everyone would be better off if instead of roundabouts, rehabilitation off northern stretch of 85 was funded back then. Would definitely save a few suspensions.
Title: Re: Over 7000 roundabouts in America
Post by: D-Dey65 on February 14, 2019, 12:56:48 AM
The Clipp Road thing is just a private pullout (you can see the property signs on the trees).  Same goes for Helderhill.
Oh, I thought those were temporary Jersey Freeway-type ramps that were planned to be upgraded. My bad.


The one west of Helderhill looks like an on-ramp from nowhere.
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 14, 2019, 09:05:40 AM
The problem with the old thread and now, predictably this one, are the videos and stories handpicked to attempt to put roundabouts in a bad light. If someone drives at 60 mph strait through a roundabout the design and theory behind the intersection is not at fault. No one makes an argument that plowing through a red light means traffic light-controlled intersections are inherently dangerous. Pixel 2

The generalization has been that roundabouts are safe and traffic signals are dangerous.  However, studies published over the past couple years have found that there are safety issues with multi-lane roundabouts.  The multi-lane roundabouts analyzed in the Minnesota study saw a 6% increase in injury crashes compared to the conventional intersections they replaced. 

The generalization that all roundabouts are safe (whether they be single-lane or multi-lane) is largely based on the IIHS study back from 2000.  As I have mentioned before, only 5 roundabouts along a 2500 foot section of Avon Road in Colorado was analyzed for injury crashes - not to mention Avon Road is only signed for 25 mph.  Yet the safety statistics found in that IIHS study (ie. 35% reduction in all crashes, 76% reduction in injury crashes, 90% reduction in fatal crashes) has been cited countless times by agencies to justify the construction of complex 2x2 and 3x2 roundabouts throughout America... and those types of roundabouts have really exploded over the past decade.  Today there are about 50 triple-lane modern roundabouts whereas 20 years ago there were zero.  The truth is those triple-lane roundabouts have been somewhat of a disaster in this country.  Many triple-lane modern roundabouts have been downsized years after being constructed.  The roundabouts that haven't been downsized are the ones where you see 150+ crashes/year.  But roundabouts are safe and traffic signals are dangerous... after all that IIHS study is 'settled science'. 
Title: Re: Over 7000 roundabouts in America
Post by: billpa on February 14, 2019, 10:53:24 AM
* You never differentiate between single and multi-lane roundabouts until you're pressed.

* Your arguments would go down better with people like me if you did away with the ridiculous videos and stories of crashes 'related' ( usually just near ) to roundabouts which a cursory read reveal are actually caused by things like excessive speed and drunk driving.

* I never said anything negative about traffic-lighted intersections. My point is I could start a silly thread about traffic light junctions with news stories about crashes that occurred in them. It wouldn't prove much if the offending driver was wasted or driving at 50 mph when the light was red.

Pixel 2

Title: Re: Over 7000 roundabouts in America
Post by: TheHighwayMan394 on February 14, 2019, 11:21:06 AM
* Your arguments would go down better with people like me if you did away with the ridiculous videos and stories of crashes 'related' ( usually just near ) to roundabouts which a cursory read reveal are actually caused by things like excessive speed and drunk driving.

I’m pretty sure at least once he did fault a roundabout when a drunk speeder launched himself airborne through the center of a roundabout, saying the dude may have been safe if it was a standard signalized intersection - ignoring that whole drunk and speeding thing.
Title: Re: Over 7000 roundabouts in America
Post by: silverback1065 on February 14, 2019, 12:14:05 PM
* You never differentiate between single and multi-lane roundabouts until you're pressed.

* Your arguments would go down better with people like me if you did away with the ridiculous videos and stories of crashes 'related' ( usually just near ) to roundabouts which a cursory read reveal are actually caused by things like excessive speed and drunk driving.

* I never said anything negative about traffic-lighted intersections. My point is I could start a silly thread about traffic light junctions with news stories about crashes that occurred in them. It wouldn't prove much if the offending driver was wasted or driving at 50 mph when the light was red.

Pixel 2

roundabouts trigger him so he finds random articles to confirmation bias him into hating them more.  numbers speak for themselves, the accidents they do have tend to be less severe than traditional ones.  a lot of accidents come from people who have no idea what they are doing in one, I can't tell you how many times people try to make a left turn from the right lane in a roundabout.  there is sufficient signage and pavement markings that make this inexcusable.   
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 14, 2019, 01:50:37 PM
* You never differentiate between single and multi-lane roundabouts until you're pressed.

I just did a forum search and I referred to ‘complex multi-lane’ roundabouts in 24 separate posts.  I keep saying the phrase “complex multi-lane” because it not only distinguishes between single-lane and multi-lane, but it also distinguishes between simplified 1x2 multi-lane roundabouts and the complex 2x2 or 2x3 types.  In one post I attempted to explain why I feel there is a fundamental crash problem at 2x2 roundabouts that you don’t see at 1x2 types.   
 
Take a look at these two pictures below.  In both cases the yellow car assumes the blue car in the inner-most lane of the roundabout will continue circulating through the roundabout (“the circular road misconception”).  With a 2x2 roundabout the assumption can lead to a crash when the blue car actually takes the red path.    However, with a 1x2 roundabout this assumption by the yellow driver doesn’t lead to a crash since both paths the blue car can take is in conflict with the yellow car (so the yellow car is forced to wait regardless.. since it's tough to squeeze two cars into one lane).

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Conflicts_zpssn3x8lpr.png)

This is a fundamental problem I see with 2x2 roundabouts.  How do you design 2x2 roundabouts so the driver in the yellow car knows that the blue car may actually be exiting the roundabout?  In too many cases the yellow car wrongfully assumes the blue car is going to continue circulating around the roundabout and pulls out… leading to a failure to yield crash.
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 14, 2019, 02:11:03 PM
* Your arguments would go down better with people like me if you did away with the ridiculous videos and stories of crashes 'related' ( usually just near ) to roundabouts which a cursory read reveal are actually caused by things like excessive speed and drunk driving.

I’m pretty sure at least once he did fault a roundabout when a drunk speeder launched himself airborne through the center of a roundabout, saying the dude may have been safe if it was a standard signalized intersection - ignoring that whole drunk and speeding thing.

The IIHS study from 20 years ago found that roundabouts reduce injury crashes by 76%.  Then a study from 2 years ago looking specifically at 2x2 multi-lane roundabouts found that injury crashes increased by 6% compared to the intersection they replaced.  Maybe i missed it, but i don't remember either study saying "drunk driving accidents" were ignored in the study.  If that's the case I don't really care if Bozo the clown walked into the middle of the roundabout, causing someone to swerve and crash.  According to these studies, a crash is a crash is a crash.  The ultimate question is do roundabouts reduce injury crashes compared to signalized intersections.  At the very least, there seems to be a subset of modern roundabouts (ie. 2x2 or 2x3 types) where the answer may be NO.
Title: Re: Over 7000 roundabouts in America
Post by: kphoger on February 14, 2019, 02:17:39 PM
numbers speak for themselves, the accidents they do have tend to be less severe than traditional ones.

↓  "Numbers" are saying more than just one thing.  ↓

a study from 2 years ago looking specifically at 2x2 multi-lane roundabouts found that injury crashes increased by 6% compared to the intersection they replaced.
Title: Re: Over 7000 roundabouts in America
Post by: froggie on February 14, 2019, 02:57:50 PM
For the study that tradephoric keeps referencing (yes I read through it), one could argue that the lack of multi-lane roundabouts studied (only 6) could be introducing a bias into the results because of the small sample size.  Very unlike the number of single-lane roundabouts studied (over 100) and unbalanced roundabouts (over 30).

It's also worth noting that, despite the small sample size of multi-lane roundabouts, none of them produced a fatality or serious injury.
Title: Re: Over 7000 roundabouts in America
Post by: kalvado on February 14, 2019, 03:02:14 PM
For the study that tradephoric keeps referencing (yes I read through it), one could argue that the lack of multi-lane roundabouts studied (only 6) could be introducing a bias into the results because of the small sample size.  Very unlike the number of single-lane roundabouts studied (over 100) and unbalanced roundabouts (over 30).

It's also worth noting that, despite the small sample size of multi-lane roundabouts, none of them produced a fatality or serious injury.
Frankly speaking, there are only that many studies of roundabouts in US. Europe seems to have a bigger pool of studies with way better understanding of do's and donot's.
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 14, 2019, 03:38:34 PM
For the study that tradephoric keeps referencing (yes I read through it), one could argue that the lack of multi-lane roundabouts studied (only 6) could be introducing a bias into the results because of the small sample size.  Very unlike the number of single-lane roundabouts studied (over 100) and unbalanced roundabouts (over 30).

The 6 multi-lane roundabouts analyzed in the Minnesota study provided 668 data points (197 crashes in the before condition; 471 crashes in the after condition).  In addition, the IIHS study that generic roundabout safety statistics are based on only analyzed 5 multi-lane roundabouts that included before/after injury crash data.  If you want to be critical of the small number of multi-lane roundabouts in the Minnesota study you should also be critical of the small number of multi-lane roundabouts analyzed in the IIHS study.

It's also worth noting that, despite the small sample size of multi-lane roundabouts, none of them produced a fatality or serious injury.

Yet they produced 7 more Level-C crashes and a whopping 270 more PDO crashes.  It's great that there were 0 Type-A crashes, but if we use FHWA’s comprehensive crash costs by injury severity level it’s still clear that the roundabouts had a higher social cost than the intersections they replaced.

(https://i.imgur.com/D77VC6z.png)
http://www.dot.state.mn.us/trafficeng/safety/docs/roundaboutstudy.pdf

BEFORE ROUNDABOUT CRASH COSTS = $4,882,600
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   3 X  $216,000 = $648,000
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   46 X $44,900 = $2,065,400
PDO (O)          133 X $7,400 =  $984,200

AFTER ROUNDABOUT CRASH COSTS = $6,546,900
Fatality (K)           0 X $4,008,900 = $0
Disabling Injury (A)   0 X  $216,000 = $0
Evident Injury (B)   15 X $79,000 = $1,185,000
Possible Injury (C)   53 X $44,900 = $2,379,700
PDO (O)          403 X $7,400 =  $2,982,200
Title: Re: Over 7000 roundabouts in America
Post by: TheHighwayMan394 on February 14, 2019, 05:18:48 PM
* You never differentiate between single and multi-lane roundabouts until you're pressed.

I just did a forum search and I referred to ‘complex multi-lane’ roundabouts in 24 separate posts.  I keep saying the phrase “complex multi-lane” because it not only distinguishes between single-lane and multi-lane, but it also distinguishes between simplified 1x2 multi-lane roundabouts and the complex 2x2 or 2x3 types.  In one post I attempted to explain why I feel there is a fundamental crash problem at 2x2 roundabouts that you don’t see at 1x2 types.   
 
Take a look at these two pictures below.  In both cases the yellow car assumes the blue car in the inner-most lane of the roundabout will continue circulating through the roundabout (“the circular road misconception”).  With a 2x2 roundabout the assumption can lead to a crash when the blue car actually takes the red path.    However, with a 1x2 roundabout this assumption by the yellow driver doesn’t lead to a crash since both paths the blue car can take is in conflict with the yellow car (so the yellow car is forced to wait regardless.. since it's tough to squeeze two cars into one lane).

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Roundabouts/Conflicts_zpssn3x8lpr.png)

This is a fundamental problem I see with 2x2 roundabouts.  How do you design 2x2 roundabouts so the driver in the yellow car knows that the blue car may actually be exiting the roundabout?  In too many cases the yellow car wrongfully assumes the blue car is going to continue circulating around the roundabout and pulls out… leading to a failure to yield crash.


Correct me if I’m wrong, but doesn’t “yield” actually mean “yield” and not “yield only if I’m going to get in the way”? One of my pet peeves is cars with a stop/yield sign who turn into the right lane while I’m simultaneously in the left lane because I don’t know if he’s going to make a wide turn or slip on ice into me or some other stupid shit because he’s too impatient to wait a few seconds. Conversely if I’m the one at the sign I don’t know if he’s going to change lanes abruptly or something either.
Title: Re: Over 7000 roundabouts in America
Post by: kalvado on February 14, 2019, 05:45:09 PM

Correct me if I’m wrong, but doesn’t “yield” actually mean “yield” and not “yield only if I’m going to get in the way”? One of my pet peeves is cars with a stop/yield sign who turn into the right lane while I’m simultaneously in the left lane because I don’t know if he’s going to make a wide turn or slip on ice into me or some other stupid shit because he’s too impatient to wait a few seconds. Conversely if I’m the one at the sign I don’t know if he’s going to change lanes abruptly or something either.
I cannot find legal definition at the moment - but as far as I remember, "yield" means that other traffic should be able to move without changing speed or intentions as if yielding vehicle is not there.
SO a car going into a different direction, or into a different lane is OK - as long as turning into a different lanes is actually required (which is another pile of fine print)
Title: Re: Over 7000 roundabouts in America
Post by: silverback1065 on February 14, 2019, 06:18:10 PM
if you reach a yield sign, you YIELD the r/w to opposing traffic. hence the name
Title: Re: Over 7000 roundabouts in America
Post by: jakeroot on February 15, 2019, 01:55:48 AM
if you reach a yield sign, you YIELD the r/w to opposing traffic. hence the name

Right but you don't need to yield to traffic that shouldn't interfere with you.
Title: Re: Over 7000 roundabouts in America
Post by: Plutonic Panda on February 15, 2019, 02:28:45 AM
if you reach a yield sign, you YIELD the r/w to opposing traffic. hence the name

Right but you don't need to yield to traffic that shouldn't interfere with you.
If only more people understood this!
Title: Re: Over 7000 roundabouts in America
Post by: english si on February 15, 2019, 06:14:56 AM
In one post I attempted to explain why I feel there is a fundamental crash problem at 2x2 roundabouts that you don’t see at 1x2 types.
As I pointed out at the time, this particular crash problem only is as bad as it is because of the idea that it is a circular road is a fallacy - which comes from one influential, but idiotic, engineer.
In regards to using a signal indication when exiting a roundabout... that was actually being discouraged by the roundabout expert in the Minnesota webinar:
Quote
“We also would never tell a driver to use a right turn signal to exit a roundabout.  Again, that’s a through movement and we don’t want to create the impression that it’s a right turn.”
If the blue car's blinkers were being used to announce where it was going, then the yellow car's driver wouldn't be confused. Which is how it is meant to work in the UK...
This is a fundamental problem I see with 2x2 roundabouts.  How do you design 2x2 roundabouts so the driver in the yellow car knows that the blue car may actually be exiting the roundabout?  In too many cases the yellow car wrongfully assumes the blue car is going to continue circulating around the roundabout and pulls out… leading to a failure to yield crash.
Design it as an ACTUAL circular road, and so exiting the roundabout requires indication (using your blinkers) to follow the rules of the road (eg 186 (https://www.gov.uk/guidance/the-highway-code/using-the-road-159-to-203), which is the British rule governing these matters) as you are turning off it!
(https://assets.digital.cabinet-office.gov.uk/media/559af891e5274a155c00001d/the-highway-code-rule-185.jpg)
Title: Re: Over 7000 roundabouts in America
Post by: kalvado on February 15, 2019, 07:43:13 AM
if you reach a yield sign, you YIELD the r/w to opposing traffic. hence the name

Right but you don't need to yield to traffic that shouldn't interfere with you.
If only more people understood this!
Problem of many roundabouts is that there are a lot of situations where interference is not clear until traffic either passes (and you didn't have to yield), or you did have to yield - but it is a property-damage only now, don't worry.

(https://assets.digital.cabinet-office.gov.uk/media/559af891e5274a155c00001d/the-highway-code-rule-185.jpg)

And the thing is that the driver in a white car cannot see blue car blinkers. Not a problem if the circle is big enough so that there is time to pass.
But many supermicrocompact circles are squeezed into existing intersections, so white car has to wait until blue one actually exits.
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 15, 2019, 08:26:15 AM
And the thing is that the driver in a white car cannot see blue car blinkers. Not a problem if the circle is big enough so that there is time to pass.  But many supermicrocompact circles are squeezed into existing intersections, so white car has to wait until blue one actually exits.

The A roundabout pictured below has a central island diameter of about 80 feet while the B roundabout has a diameter of about 100 feet.  Even though the A roundabout is more compact, the design of "straight out" exits helps separate traffic between each leg of the roundabout.

(https://i.imgur.com/9JhlTTM.jpg)


And here's a redesign i made up of a crash prone triple-lane roundabout in Michigan.  The same idea applies here with separating legs of traffic with "straight out" exits.  Also designing the central island to be more "rectangular" than circular i believe could be beneficial.

(https://i.imgur.com/OsKh4no.jpg)
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 15, 2019, 11:04:49 AM
The bypass has been a great improvement.  The light at Blessing Road was horrendous and almost seemed unnecessary; the roundabout there has been most welcome.  Getting through the lights on New Scotland was annoying and, although there were quite a number of fender benders due to human error at the get-go, I haven't seen an accident at the NY 85/NY 140 roundabout in a very long time (tradephoric likes to focus on the accident-prone transition period and ignore when accident dropoffs happen at those same sites).

Actual crash data would make any argument you are trying to make more powerful.  You personally not seeing a roundabout accident in a very long time just doesn't cut it.  Here is a list of the 20 most crash prone intersections in Michigan in 2017.

https://www.freep.com/story/news/local/michigan/2018/05/11/michigan-most-dangerous-intersections/602137002/

The triple-lane roundabouts at 18 1/2 and Van Dyke (constructed about 15 years ago now) is the #2 most crash prone intersection in Michigan... and it doesn't come close to carrying an extensive amount of traffic to justify that high ranking.  That just happens to be the roundabout i attempted to redesign in the previous post.  The other triple-lane roundabouts in Michigan are #4 and #5 on that list.  There use to be 7 triple-lane roundabouts in Michigan, but 4 of them were downsized to 2x2.  The 3 that remain have horrible crash rates. 

Title: Re: Over 7000 roundabouts in America
Post by: Rothman on February 15, 2019, 11:44:53 AM
Oh, so despite my very routine trips up and down those roundabouts, you think all the crashes I saw are just happening at the same rate at different times of the day?  That is less powerful, actually.  At least I have my observations.  You don't even have that in your rebuttal regarding NY 85.

I also suspect that since you were able to find crash statistics on the NY 85/NY 140 shortly after the roundabout opened and you touted it's high crash rate that your refusal to look into that particular data again may be evidence of data cherry picking to support your crusade.
Title: Re: Over 6000 roundabouts in America
Post by: Paulinator66 on February 15, 2019, 11:55:43 AM
Actual roundabouts, or just little bitty islands in the middle of the intersections?

While travelling in Ireland last year there were roundabouts everywhere, as you would expect, but there was one intersection that was so small there was simply a 2 foot diameter circle painted in the middle of an otherwise normal looking American intersection.  I still drove around it though.
Title: Re: Over 6000 roundabouts in America
Post by: abefroman329 on February 15, 2019, 12:17:10 PM
Actual roundabouts, or just little bitty islands in the middle of the intersections?

While travelling in Ireland last year there were roundabouts everywhere, as you would expect, but there was one intersection that was so small there was simply a 2 foot diameter circle painted in the middle of an otherwise normal looking American intersection.  I still drove around it though.
It's known as a mini-roundabout, and they're pretty common in the UK.  I think the principle is "yield to whoever is in the intersection before proceeding," since there's really no way to traverse the intersection in a circular fashion.
Title: Re: Over 7000 roundabouts in America
Post by: kalvado on February 15, 2019, 12:20:26 PM
Oh, so despite my very routine trips up and down those roundabouts, you think all the crashes I saw are just happening at the same rate at different times of the day?  That is less powerful, actually.  At least I have my observations.  You don't even have that in your rebuttal regarding NY 85.

I also suspect that since you were able to find crash statistics on the NY 85/NY 140 shortly after the roundabout opened and you touted it's high crash rate that your refusal to look into that particular data again may be evidence of data cherry picking to support your crusade.
Crash data is difficult to come by. It usually comes as "worst intersections in the area"
At that point, 85's circles made the list, so data was readily available. I don't know where to look for those numbers outside of querying DOT, police or someone else along those lines.
Traffic counts are there for everyone to look at (fun fact: data on I-81 viaduct area is no longer there); accidents are not.
Actually you may have a better idea where to start.
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 15, 2019, 12:26:58 PM
Oh, so despite my very routine trips up and down those roundabouts, you think all the crashes I saw are just happening at the same rate at different times of the day?  That is less powerful, actually.  At least I have my observations.  You don't even have that in your rebuttal regarding NY 85.

For all i know the response time at clearing vehicles off the roadway after a roundabout crash has improved significantly, reducing the likelihood of you observing the aftermath of a crash.  After all they have plenty of experience dealing with crashes at the roundabout.  I've personally witnessed a vehicle flipped over at one of the crash prone roundabouts in Michigan, with EMS tending to the driver as he was bleeding profusely from his arm.  That's my personal anecdotal experience.  But me observing one injury accident doesn't tell me much about how the roundabout performs overall over the course of an entire year.  That's why years worth of crash data is useful for analysis. 

I also suspect that since you were able to find crash statistics on the NY 85/NY 140 shortly after the roundabout opened and you touted it's high crash rate that your refusal to look into that particular data again may be evidence of data cherry picking to support your crusade.

You are the one making the argument that i only focus on the accident-prone transition period (ie. the initial spike in accidents after a roundabout is first completed) and ignore when accidents drop off.  Yet I've cited the 18 1/2 Mile & Van Dyke roundabout several times in the past for its high crash rate... and that roundabout is nearly 15 years old.  The transitional period is long over. 

If there was a huge drop off in crashes at the NY 85/NY 140 roundabout then great.  All i know is i have yet to find a 2x2 roundabout with a crash rate below 1.0 MEV whether it's 2 years old or 20.  A crash rate of 1.0 MEV is higher than the average crash rate of signalized intersections... so you would think there would at least be a few multi-lane roundabouts with crash rates below that.  There are now literally hundreds of 2x2 or 2x3 roundabouts in America.  Just cite one with a crash rate below 1.0 MEV (and i don't care about how old it is).  A 2x2 roundabout with a low crash rate is like the mythical unicorn or bigfoot... maybe it exists.
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 15, 2019, 12:46:55 PM
^Think of it this way.  A crash rate of 1 MEV equates to 1 accident per million entering vehicles.  Just watch 20 cars go through a complex roundabout and you'll probably already witness a near miss.  You really think a million vehicles are going to navigate the roundabout without crashing into each other at least once?   There are too many ways for drivers to screw up at these complex roundabouts.  I'm not hiding anything from you.
Title: Re: Over 7000 roundabouts in America
Post by: BrianP on February 15, 2019, 02:01:27 PM
Just cite one with a crash rate below 1.0 MEV (and i don't care about how old it is). 
Does this one count?
MD450@MD435/MD387
https://www.google.com/maps/place/MD-435,+Annapolis,+MD/@38.976196,-76.5051311,114m/data=!3m1!1e3!4m5!3m4!1s0x89b7f6561b3a54a5:0x10eaff58740622a3!8m2!3d38.9831055!4d-76.5054642

From figure 3: ( I think this column has the value you're referring to, which is accident rate / MVE)
before: 1.52
after: 0.66
https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa09027/resources/Marylands%20Roundabouts%20Accident%20Experience%20and%20Economic%20Evaluation.pdf
I wish there was data for more recent years.

I think taking severity of a crash into account should be looked at more than just a raw accident count.    Having more fender benders is worth it when significantly reducing the number of severe crashes.  I think that's the trade off with roundabouts which is worth it.  The worst crashes that I see are usually the left turns at non-roundabouts.

That said I think Maryland agrees with you about larger roundabouts.  There are no 3x roundabouts that I've found.  And even 2x are rare.  They mostly do 1x or half 2x.  I'd like to see data for this roundabout, which is the most 2x like roundabout I know of in MD:
https://www.google.com/maps/@39.2517845,-76.7143174,159m/data=!3m1!1e3
Even that may not meet a strict interpretation of 2x. Since the inner lane of the roundabout never 'exits'.  It doesn't 'exit' since you have to cross a dotted line to exit from the inner lane.  That makes it seem like they prefer that you change to the outer lane before exiting to avoid the problem covered above. 
Title: Re: Over 7000 roundabouts in America
Post by: kphoger on February 15, 2019, 02:09:04 PM
Looks like a 2x2 roundabout to me.  Every approach is two lanes, and the entire circulating roadway is two lanes wide (exact striping varies around the circle but true nonetheless).
Title: Re: Over 7000 roundabouts in America
Post by: english si on February 15, 2019, 02:18:55 PM
Actual roundabouts, or just little bitty islands in the middle of the intersections?

While travelling in Ireland last year there were roundabouts everywhere, as you would expect, but there was one intersection that was so small there was simply a 2 foot diameter circle painted in the middle of an otherwise normal looking American intersection.  I still drove around it though.
It's known as a mini-roundabout, and they're pretty common in the UK.  I think the principle is "yield to whoever is in the intersection before proceeding," since there's really no way to traverse the intersection in a circular fashion.
In the UK, it's 'give way to right', the same as big roundabouts (Ireland is, I believe, the same - though they do love to be different just to be different from the UK - eg diamond warning signs). And you are meant to drive around them, but you can drive over them.
Title: Re: Over 7000 roundabouts in America
Post by: abefroman329 on February 15, 2019, 02:25:02 PM
In the UK, it's 'give way to right'
That's what I thought.

Apparently in France, traffic in the roundabout yields to traffic entering the roundabout, which makes no sense at all.
Title: Re: Over 7000 roundabouts in America
Post by: kphoger on February 15, 2019, 02:33:15 PM
Apparently in France, traffic in the roundabout yields to traffic entering the roundabout, which makes no sense at all.

I believe that depends.  At older traffic circles in urban areas, traffic in the circle yields to entering traffic.  However, France has a zillion newer roundabouts where entering traffic yields to traffic in the circle.  Basically, it's similar to the USA:  it all depends on the location.
Title: Re: Over 7000 roundabouts in America
Post by: jakeroot on February 15, 2019, 02:40:43 PM
Just cite one with a crash rate below 1.0 MEV (and i don't care about how old it is). 
Does this one count?
MD450@MD435/MD387
https://www.google.com/maps/place/MD-435,+Annapolis,+MD/@38.976196,-76.5051311,114m/data=!3m1!1e3!4m5!3m4!1s0x89b7f6561b3a54a5:0x10eaff58740622a3!8m2!3d38.9831055!4d-76.5054642

From figure 3: ( I think this column has the value you're referring to, which is accident rate / MVE)
before: 1.52
after: 0.66
https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa09027/resources/Marylands%20Roundabouts%20Accident%20Experience%20and%20Economic%20Evaluation.pdf
I wish there was data for more recent years.

I think taking severity of a crash into account should be looked at more than just a raw accident count.    Having more fender benders is worth it when significantly reducing the number of severe crashes.  I think that's the trade off with roundabouts which is worth it.  The worst crashes that I see are usually the left turns at non-roundabouts.

That said I think Maryland agrees with you about larger roundabouts.  There are no 3x roundabouts that I've found.  And even 2x are rare.  They mostly do 1x or half 2x.  I'd like to see data for this roundabout, which is the most 2x like roundabout I know of in MD:
https://www.google.com/maps/@39.2517845,-76.7143174,159m/data=!3m1!1e3
Even that may not meet a strict interpretation of 2x. Since the inner lane of the roundabout never 'exits'.  It doesn't 'exit' since you have to cross a dotted line to exit from the inner lane.  That makes it seem like they prefer that you change to the outer lane before exiting to avoid the problem covered above. 
Looks like a 2x2 roundabout to me.  Every approach is two lanes, and the entire circulating roadway is two lanes wide (exact striping varies around the circle but true nonetheless).

The West/Spa/Taylor roundabout in Annapolis is a 2x1 roundabout. The West St approaches are two lanes, and both may proceed through. But, the Taylor and Spa approaches are, while two lane, only single lane through movements (both right lanes on those approaches are right-only).

In tradephoric's language, this does not make it a complex multi-lane roundabout.

The MD-45 Towson oval roundabout is also on that list, and crashes went up quite a bit there. Thing is, the study's from 2004, before it was modified. But even before, I don't think it was a 2x2 roundabout (only ever 2x1, if that).
Title: Re: Over 7000 roundabouts in America
Post by: kphoger on February 15, 2019, 02:57:43 PM
But, the Taylor and Spa approaches are, while two lane, only single lane through movements (both right lanes on those approaches are right-only).

Yep, I missed that.
Title: Re: Over 7000 roundabouts in America
Post by: jakeroot on February 15, 2019, 03:09:56 PM
But, the Taylor and Spa approaches are, while two lane, only single lane through movements (both right lanes on those approaches are right-only).

Yep, I missed that.

Though it is interesting how many roundabouts in Maryland were apparently built to accommodate two lanes around the entirety of the circle, but are mostly fed only by one lane on two of the approaches, and two on the other two.
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 15, 2019, 03:12:10 PM
Just cite one with a crash rate below 1.0 MEV (and i don't care about how old it is). 
Does this one count?
MD450@MD435/MD387
https://www.google.com/maps/place/MD-435,+Annapolis,+MD/@38.976196,-76.5051311,114m/data=!3m1!1e3!4m5!3m4!1s0x89b7f6561b3a54a5:0x10eaff58740622a3!8m2!3d38.9831055!4d-76.5054642

From figure 3: ( I think this column has the value you're referring to, which is accident rate / MVE)
before: 1.52
after: 0.66
https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa09027/resources/Marylands%20Roundabouts%20Accident%20Experience%20and%20Economic%20Evaluation.pdf
I wish there was data for more recent years.

Traffic in the right most lane is striped to exit onto West St (so technically only one lane of traffic circulates around the circle along that leg).  But really the only thing preventing it from being a full 2x2 roundabout is the pavement markings.  The real point i wanted to make regarding that circle is the upstream geometry.  The roadway only widens out to two lanes in each direction just before the roundabout.  Otherwise drivers are driving along on a two-way street signed for 25 mph.  There is another multi-lane roundabout in Figure 3 that supposedly has a 0.0 crash rate but i can't even find it.... where is MD139@ Bellona Ave?
Title: Re: Over 7000 roundabouts in America
Post by: english si on February 15, 2019, 03:12:34 PM
Though it is interesting how many roundabouts in Maryland were apparently built to accommodate two lanes around the entirety of the circle, but are mostly fed only by one lane on two of the approaches, and two on the other two.
In Britain we have a lot of roundabouts that can accommodate two lanes with all the approaches being one lane until just before the roundabout.
Title: Re: Over 7000 roundabouts in America
Post by: kphoger on February 15, 2019, 03:23:43 PM
There is another multi-lane roundabout in Figure 3 that supposedly has a 0.0 crash rate but i can't even find it.... where is MD139@ Bellona Ave?

http://roundabout.kittelson.com/Roundabouts/Details/82 (http://roundabout.kittelson.com/Roundabouts/Details/82)
Status = removed
Title: Re: Over 7000 roundabouts in America
Post by: froggie on February 15, 2019, 10:01:47 PM
139 at Bellona was never a full 2x2 roundabout.  Westbound-to-southbound was the only part of the roundabout that had 2 lanes.  It was removed ca. 2011-12 when the ramp to 695 was separated from the leg of Bellona west of Charles St.
Title: Re: Over 7000 roundabouts in America
Post by: mrsman on February 17, 2019, 09:09:48 PM
139 at Bellona was never a full 2x2 roundabout.  Westbound-to-southbound was the only part of the roundabout that had 2 lanes.  It was removed ca. 2011-12 when the ramp to 695 was separated from the leg of Bellona west of Charles St.

Here's a picture:

https://www.google.com/maps/@39.4180381,-76.629021,3a,75y,217.34h,73.94t/data=!3m7!1e1!3m5!1swkk5EobPLecXSnMi5xUhhg!2e0!6s%2F%2Fgeo1.ggpht.com%2Fcbk%3Fpanoid%3Dwkk5EobPLecXSnMi5xUhhg%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D208.5173%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656


What seems extremely complicated is that there seems to be 3 (or 4) places near Baltimore where Ballona and Charles intersect.

But I think what they did to this intersection is a big improvement.  The roundabout was not helpful.
Title: Re: Over 7000 roundabouts in America
Post by: BrianP on February 19, 2019, 04:36:01 PM
But, the Taylor and Spa approaches are, while two lane, only single lane through movements (both right lanes on those approaches are right-only).

Yep, I missed that.
Thanks.  Usually when it's a 2x1 it's easier to tell from the ground markings like this one:
https://www.google.com/maps/@39.1456596,-76.9039883,91m/data=!3m1!1e3
Title: Re: Over 7000 roundabouts in America
Post by: jakeroot on February 19, 2019, 11:24:22 PM
But, the Taylor and Spa approaches are, while two lane, only single lane through movements (both right lanes on those approaches are right-only).

Yep, I missed that.
Thanks.  Usually when it's a 2x1 it's easier to tell from the ground markings like this one:
https://www.google.com/maps/@39.1456596,-76.9039883,91m/data=!3m1!1e3

Haha I spent an inordinate amount of time studying that interchange last week, trying to see if any of the roundabouts operated in 2x2 configuration. As far as I can tell, though they used to lack striping (http://bit.ly/2TXbwgv), none of the roundabouts through there ever had four 2-lane entrances.
Title: Re: Over 7000 roundabouts in America
Post by: tradephoric on February 21, 2019, 12:42:02 PM
Saw the title of the thread changed numbers, let me know when it’s over 9,000. 

Depending how strict of a definition you want to use for "modern roundabout", i bet you we are close to 9,000 today.  Just think of how many little subdivision roundabouts like this haven't been documented:

https://www.google.com/maps/@33.1405037,-96.8720605,110m/data=!3m1!1e3