Even these guys' simple test is an eye-opener. And they did not even measure the time delays of vehicles waiting in line to go through the 4-way STOP v. the roundabout.
Enjoy!
Mike
A roundabout is usually instead of a traffic light, not instead of a 4-way stop.
(I will not spoil the final result of the video.)
Quote from: 1 on September 14, 2013, 05:46:05 PM
A roundabout is usually instead of a traffic light, not instead of a 4-way stop.
That's...a bit of a generalization
A roundabout is a 4-way yield, so of course it's more efficient than a 4-way stop.
I think the real myth is that Americans have little exposure to or experience with roundabouts. Seems like every week for the past 10 or 15 years now, a new roundabout has opened somewhere in the U.S. with an accompanying news article about how confused drivers are by the technique. Confused they may indeed be, but I think the reason for that can no longer be that roundabouts are new or rare in this country.
Quote from: corco on September 14, 2013, 05:59:54 PM
Quote from: 1 on September 14, 2013, 05:46:05 PM
A roundabout is usually instead of a traffic light, not instead of a 4-way stop.
That's...a bit of a generalization
Massachusetts is home to a number of roundabouts and even more of its bigger cousin, the dreaded rotary. In my experience usually a light takes the place of a rotary or a roundabout takes the place of a light. I do not know of any instances of using a roundabout instead of a 4 way stop. In such a case of upgrading a 4-way however, I'm sure the delays and level of service provided by a light vs. a roundabout would be analyzed. Usually, the roundabout wins.
Right, in Arizona though where I lived recently, roundabouts were always used in place of four way stops where traffic volume wouldn't warrant a stoplight, like so http://goo.gl/maps/WExDo. I know of one exception:
http://goo.gl/maps/Uj9lV
Actually, I could be wrong on this- when I think of all the roundabouts on SR 89/89A/179 up around Sedona and Prescott, those are often used in lieu of stoplights.
Other states I've lived in...I think Washington had some in lieu of stoplights but also some in lieu of four way stops, there aren't enough of them that I've seen in Montana or Wyoming to really tell, Idaho had a few in lieu of four way stops.
There's going to be a roundabout at the intersection of US 62 and the new US 27 bypass of Cynthiana, Ky. The intersection is in somewhat of a rural area. I suspect the roundabout may have been installed in lieu of stop signs on US 62.
Roundabouts are ok in some places, but it seems they need more real estate and don't always mix well with pedestrians.
In Indiana, it seems north of Indianapolis and Bloomington are fairly aggressive with using them.
Because of traffic counts dictating widths, 1-lane roundabouts are often used in lieu of a 4-way stop while roundabouts with 2 or more lanes are usually used in lieu of a traffic signal.
What about Roundabouts vs clover leafs? in some places the UK over does Roundabouts where they need more grade separation
Quote from: andy on September 14, 2013, 08:55:08 PM
Roundabouts are ok in some places, but it seems they need more real estate and don't always mix well with pedestrians.
In Indiana, it seems north of Indianapolis and Bloomington are fairly aggressive with using them.
Roundabouts don't have to be small. See the miniroundabouts that are common in the UK. It's basically a painted circle in the middle of a small intersection and forces drivers to use roundabout rules (yield to cars on the right) at what would be a 4-way stop in the US.
Quote from: realjd on September 14, 2013, 11:22:46 PM
Quote from: andy on September 14, 2013, 08:55:08 PM
Roundabouts are ok in some places, but it seems they need more real estate and don't always mix well with pedestrians.
In Indiana, it seems north of Indianapolis and Bloomington are fairly aggressive with using them.
Roundabouts don't have to be small. See the miniroundabouts that are common in the UK. It's basically a painted circle in the middle of a small intersection and forces drivers to use roundabout rules (yield to cars on the right) at what would be a 4-way stop in the US.
I think you meant "can be small". Would that be much different than some type of 4 way yield, to which I would not be opposed. My apologies to law enforcement, but how much gas and time could be saved if rolling stops (where reasonable and safe) were permitted.
I am still not convinced that roundabouts are a good substitute for a very busy intersection with high traffic volume. I think that traffic signals with a proper traffic flow control system (ITS) are more efficient in areas where volume is high. In Carmel Indiana it works ok at "MOST" of the roundabouts they have put in. but there are some glaring failures where they roundabout has caused traffic backups. Such as the closely spaced roundabouts at 116th and Springmill and 116th and Illinois which are located west of US-31 https://maps.google.com/maps?q=116th+and+meridian&rlz=1C1AVSX_enUS390US395&um=1&ie=UTF-8&hl=en&sa=N&tab=wl (https://maps.google.com/maps?q=116th+and+meridian&rlz=1C1AVSX_enUS390US395&um=1&ie=UTF-8&hl=en&sa=N&tab=wl) If we were to put these kind of roundabouts in at Allisonville and 82nd street or Michigan and 86th street they would be likely disastrous to traffic flow during peak periods. Same as in Citrus Heights CA. if we replaced the signals along Sunrise Blvd from Madison all the way to Roseville CA, there would be serious traffic jams at Madison Ave, Greenback Lane, Old Auburn, Antelope Road, etc. as well as bumper to bumper traffic along Sunrise Blvd. a street that is usually very heavily traveled most all hours throughout the daytime.
Quote from: corco on September 14, 2013, 05:59:54 PMQuote from: 1 on September 14, 2013, 05:46:05 PMA roundabout is usually instead of a traffic light, not instead of a 4-way stop.
That's...a bit of a generalization
It is, but there is a very wide AADT range for which roundabouts and traffic signals are essentially interchangeable as intersection treatments, with stoplights having an advantage for unbalanced flows while roundabouts generally lead to less frequent and less severe side-impact crashes. Four-way stops, on the other hand, are able to cater only for a narrow AADT range at the low end.
Perhaps a more precise way of expressing the distinction is to say that while roundabouts can replace traffic lights and four-way stops in some circumstances, a four-way stop is unlikely to work well as a substitute either for traffic lights or a roundabout.
Quote from: corco on September 14, 2013, 07:58:16 PMOther states I've lived in...I think Washington had some in lieu of stoplights but also some in lieu of four way stops, there aren't enough of them that I've seen in Montana or Wyoming to really tell, Idaho had a few in lieu of four way stops.
It's been ten years since I was last in Washington state (other than to change planes), but I don't remember actually seeing any roundabouts deployed at intersections where the flows were blatantly too heavy for a four-way stop. This was the only roundabout I personally drove when I was last in Washington state, and traffic flows seemed light enough (at least in off-peak) to be handled by a four-way stop:
I-5 off-ramp at SR 510 (https://maps.google.com/maps?q=Yelm,+WA&ie=UTF8&hq=&hnear=Yelm,+Thurston,+Washington&ll=47.061239,-122.768875&spn=0.000919,0.002411&t=m&z=19&vpsrc=6)
This, on the other hand, seems to handle flows heavy enough to justify a traffic signal as an alternate to the roundabout:
SR 510 at Pacific Ave. SE and Marvin Way (https://maps.google.com/maps?q=Yelm,+WA&ie=UTF8&hq=&hnear=Yelm,+Thurston,+Washington&ll=47.039343,-122.76475&spn=0.000927,0.002411&t=m&z=19&vpsrc=6)
In Kansas I have never personally seen a roundabout used at a location where the traffic volumes were heavy enough to justify a signal. KDOT has typically used roundabouts in the following scenarios:
* Rural highway intersections with bad accident records--typically as a replacement for stop control (which handles the volumes adequately if not in complete safety)
* As part of diamond interchanges in rural areas (e.g., US 75 north of Topeka) or in small towns (e.g., I-135 in Newton), generally at locations previously handled with stop control
Roundabouts are also used in urban areas in Kansas. The roundabouts I am familiar with in Wichita, Topeka, and Manhattan are all in neighborhoods or on rural arterials where stop control (either two- or four-way) would have been used as an alternative.
There was a proposal to include a roundabout in the Turnpike/Kellogg/Webb interchange reconstruction in Wichita, but it was shot down in part because the design was considered too experimental for the heavy flows that needed to be accommodated. So although Kansas was one of the early pioneers in roundabout development, I sense a reluctance to use them for heavy flows that is only just now starting to fade. Kansas is nowhere near as aggressive in this regard as, say, Wisconsin, where US 41 is being built with multiple interchanges where multi-lane roundabouts are designed to handle quite heavy traffic volumes and have overhead signing to provide added positive guidance (similar in function if not appearance to the Queensland
MUTCD-style multi-lane roundabout diagrammatics used around Prescott in Arizona).
Quote from: empirestate on September 14, 2013, 06:35:19 PMI think the real myth is that Americans have little exposure to or experience with roundabouts. Seems like every week for the past 10 or 15 years now, a new roundabout has opened somewhere in the U.S. with an accompanying news article about how confused drivers are by the technique. Confused they may indeed be, but I think the reason for that can no longer be that roundabouts are new or rare in this country.
Considered at the national level, roundabouts are not rare in any absolute sense, nor are they novel any longer. But there is still very broad regional variation both in how frequently they are used overall, and how frequently they are used for heavy flows. Wisconsin probably represents one extreme: roundabouts used for preference (signals can be used only if specially justified), and roundabouts routinely used at very busy intersections. At the other extreme you have agencies like TxDOT: I can count on the fingers of one hand the number of contracts for roundabouts on the Texas state highway system I have seen in the last ten years (extent of the system is close to 80,000 miles and there are probably about 1000 contract advertisements annually). Most other state DOTs, including Kansas DOT--which was one of the early adopters and is very active in research on how to adapt roundabouts for overweight/overdimensional loads owing to the heavy wind industry in Kansas--are somewhere in the middle.
So, put simply, I don't think roundabouts are anywhere near "finding their level" as an intersection treatment in the US as a whole, so it doesn't really surprise me that they still cause localized confusion more than 20 years after the early experiments in Summerlin.
Having taken traffic engineering classes and calculated delay and capacity for all-way stops and roundabouts (by hand, no less), I can confidently say the Mythbusters' findings are valid. I think this explains the benefit of roundabouts over stop control better than formulas and data ever could.
What would have been even more interesting to see is whether their results would have been much different if they used a 2-lane setup...
Nevada has embraced the roundabout concept and has tried them in a number of urban and rural locations. There have been very few intersections where one hasn't improved traffic flow, and this goes for installations that have replaced both all-way stops as well as traffic signals. It has become pretty standard practice by NDOT and several local agencies to evaluate a roundabout as a potential option when looking at intersection improvements--however, they aren't promoting or installing them nearly as aggressively as, say Wisconsin has along the US 41 corridor.
Quote from: J N Winkler on September 15, 2013, 12:38:33 AM
So, put simply, I don't think roundabouts are anywhere near "finding their level" as an intersection treatment in the US as a whole, so it doesn't really surprise me that they still cause localized confusion more than 20 years after the early experiments in Summerlin.
For those that don't know, 'Summerlin' is a master-planned community in Las Vegas, NV, which is home to the first two "modern" roundabouts in the United States. I believe they were installed in 1990. Since the initial installation, Las Vegas (and the Summerlin area in particular) have had a number of roundabouts installed.
Town Center Drive & Village Center Circle (https://maps.google.com/maps?ll=36.189542,-115.303453&spn=0.001608,0.00284&t=k&z=19)
This is the biggest of those initial two roundabouts. Town Center is one of the major north/south streets in Summerlin, departing to the southwest--it has a freeway interchange about 1/4 from this location. The physical characteristics of this roundabout have not changed since original construction (to my knowledge), but striping has changed for additional guidance. I think it started off as partially 3-lane circulation (it may not have had any internal markings when it first opened) but now operates as a two-lane.
Town Center Drive & Hualapai Way (https://maps.google.com/maps?hl=en&ll=36.178618,-115.317258&spn=0.003217,0.005681&sll=36.189193,-115.30423&sspn=0.006434,0.011362&mra=mr&t=h&z=18)
This is a later roundabout in Summerlin about 1 mile southwest of the previous one. I think it was built in the early 2000s. Both Town Center and Hualapai are 3-lane arterials on all legs of this, but the right lane on each approach is a dedicated right turn separated from the circular roadway so it actually functions as a 2-lane roundabout. This intersection was built as a roundabout at initial construction, but would likely have been a signalized intersection if built in any other part of town. It operates very effectively (note that there is a hospital in the northern quadrant, so a significant traffic generator is nearby). Part of this is attributable to much more adequate signage and lane markings providing positive guidance to drivers.
As someone from Bend, OR (practically the king of roundabouts in the US, or at least the western states), roundabouts are definitely more efficient than 4 way stops in most situations. I like them.
What struck me was the observation that was noted in the clip that many more vehicles were in the intersection at the same time, as many as six, with the roundabout v. the 4-way STOP, meaning that they are likely getting through the intersection much more quickly.
Mike
Couldn't see the vid, of course (#LifeAtSea), but judging from the comments, sounds like it reinforces the concept that roundabouts are efficient.
I'd be interested to know what the results of a traffic light would be with their tests, especially since an intersection handling that many cars would have one in my area.
Quote from: vdeane on September 15, 2013, 11:55:27 AM
I'd be interested to know what the results of a traffic light would be with their tests, especially since an intersection handling that many cars would have one in my area.
that depends on the traffic signal. Some signals are set so stupid that you have to wait 1-2 minutes while no cross traffic is passing by for a green light. this is typical with timed signals as opposed to video/loop detection.
Quote from: Indyroads on September 15, 2013, 12:34:45 PM
Quote from: vdeane on September 15, 2013, 11:55:27 AM
I'd be interested to know what the results of a traffic light would be with their tests, especially since an intersection handling that many cars would have one in my area.
that depends on the traffic signal. Some signals are set so stupid that you have to wait 1-2 minutes while no cross traffic is passing by for a green light. this is typical with timed signals as opposed to video/loop detection.
That is also typical of every single signal in my city.
Quote from: Indyroads on September 15, 2013, 12:34:45 PM
Quote from: vdeane on September 15, 2013, 11:55:27 AM
I'd be interested to know what the results of a traffic light would be with their tests, especially since an intersection handling that many cars would have one in my area.
that depends on the traffic signal. Some signals are set so stupid that you have to wait 1-2 minutes while no cross traffic is passing by for a green light. this is typical with timed signals as opposed to video/loop detection.
An adaptive traffic signal can still be quite inefficient. Consider a 4-phased intersection. Each phase is going to have roughly 5 seconds of wasted time (~3 seconds wasted time for safety clearances and ~2 seconds wasted start up time). A 4-phased intersection that is running a 100 second dial has roughly 20% of wasted time where nobody is moving through the intersection.
In addition, a side-street pedestrian phase can greatly reduce the efficiency of an adaptive intersection. A side-street pedestrian crossing of 150 feet (which is not uncommon) would require 50 seconds to allow the pedestrian to safely cross. Due to the pedestrian clearance intervals, a side-street that may only require 15-20 seconds to clear out the vehicle traffic would still need to run a full 50 seconds to fit the peds. Adaptive signals aren't really that adaptive when you consider all the safety minimums that must be satisfied each cycle. An adaptive system also requires accurate working detection which isn't always the case (loops break, inaccurate traffic counts with video detection, broken push buttons, etc. etc.).
I went thru this intersection/roundabout recently. And as luck would have it, the aerial photo shows the older configuration, and GSV shows the newer configuration.
This is Spring Valley Road, which goes from US 322 to US 202 in the Concordville, PA area.
The old intersection, which was a 4 way stop: http://goo.gl/maps/VlFS8
The new roundabout...with a 4 way stop! http://goo.gl/maps/EQv15
I love roundabouts. My biggest beef with American roundabouts is with drivers who fail to signal. If signals are used properly, other drivers need never guess at what you will do, such that traffic moves more efficiently. If you fail to signal, it freezes entering drivers who don't know whether you plan to exit and so have to freeze in case you stay on the roundabout.
:hmmm:
Quote from: jeffandnicole on September 15, 2013, 07:47:18 PM
I went thru this intersection/roundabout recently. And as luck would have it, the aerial photo shows the older configuration, and GSV shows the newer configuration.
This is Spring Valley Road, which goes from US 322 to US 202 in the Concordville, PA area.
The old intersection, which was a 4 way stop: http://goo.gl/maps/VlFS8
The new roundabout...with a 4 way stop! http://goo.gl/maps/EQv15
So i could place a flower planter in the middle of an intersection and call it a roundabout?
If Quebec can build this thing... http://goo.gl/maps/ofGLZ
Quote from: vdeane on September 15, 2013, 08:19:43 PM
If Quebec can build this thing... http://goo.gl/maps/ofGLZ
Post that in the thread about keeping traffic moving at a red light!
Quote from: tradephoric on September 15, 2013, 08:16:12 PM
So i could place a flower planter in the middle of an intersection and call it a roundabout?
It it's marked as one, yes.
http://www.lowellsun.com/news/ci_24099795/pepperell-board-votes-against-pursuing-rotary?source=rss_emailed
Here is an example of a small town political board voting against a roundabout without any traffic engineering study being done. One possible reason is that they refer to it as a "rotary" which in Massachusetts is different from a "roundabout" (mostly in size and speed of travel). "Rotary" has a somewhat negative connotation in Mass due to some notorious ones that were locations of frequent traffic jams. I think the intent in this case was to use a "roundabout" to replace the multi-way (not all way) stop.
The intersection in question is here: https://maps.google.com/maps?hl=en&ll=42.666829,-71.573369&spn=0.001803,0.004013&t=h&z=18
My opinion is that if they did do a true traffic study the engineers would find that a roundabout would be more efficient than the current configuration.
Quote from: mass_citizen on September 16, 2013, 12:08:17 AM
http://www.lowellsun.com/news/ci_24099795/pepperell-board-votes-against-pursuing-rotary?source=rss_emailed
Here is an example of a small town political board voting against a roundabout without any traffic engineering study being done. One possible reason is that they refer to it as a "rotary" which in Massachusetts is different from a "roundabout" (mostly in size and speed of travel). "Rotary" has a somewhat negative connotation in Mass due to some notorious ones that were locations of frequent traffic jams. I think the intent in this case was to use a "roundabout" to replace the multi-way (not all way) stop.
The intersection in question is here: https://maps.google.com/maps?hl=en&ll=42.666829,-71.573369&spn=0.001803,0.004013&t=h&z=18
My opinion is that if they did do a true traffic study the engineers would find that a roundabout would be more efficient than the current configuration.
From looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.
Quote from: vdeane on September 15, 2013, 08:19:43 PM
If Quebec can build this thing... http://goo.gl/maps/ofGLZ
That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.sabre-roads.org.uk%2Fwiki%2Fimages%2Fthumb%2F7%2F75%2FTiny_mini_roundabout_1_-_Coppermine_-_4700.JPG%2F799px-Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG&hash=6566b988c12c4a72a52578f8acf351ea734d529b) (http://www.sabre-roads.org.uk/wiki/index.php?title=File:Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG)
Quote from: spooky on September 16, 2013, 12:55:42 PMFrom looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.
As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.
Quote from: english si on September 16, 2013, 01:50:25 PM
That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.sabre-roads.org.uk%2Fwiki%2Fimages%2Fthumb%2F7%2F75%2FTiny_mini_roundabout_1_-_Coppermine_-_4700.JPG%2F799px-Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG&hash=6566b988c12c4a72a52578f8acf351ea734d529b) (http://www.sabre-roads.org.uk/wiki/index.php?title=File:Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG)
Yeah... I can just see how that'll work here, around Chicago. Countdown until the first T-bone accident in 5..4..3..2..1...
Quote from: english si on September 16, 2013, 01:50:25 PM
Quote from: spooky on September 16, 2013, 12:55:42 PMFrom looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.
As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.
I think I can see what you're suggesting, but I don't see how you bring Railroad St into it.
Quote from: english si on September 16, 2013, 01:50:25 PM
Quote from: vdeane on September 15, 2013, 08:19:43 PM
If Quebec can build this thing... http://goo.gl/maps/ofGLZ
That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.sabre-roads.org.uk%2Fwiki%2Fimages%2Fthumb%2F7%2F75%2FTiny_mini_roundabout_1_-_Coppermine_-_4700.JPG%2F799px-Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG&hash=6566b988c12c4a72a52578f8acf351ea734d529b) (http://www.sabre-roads.org.uk/wiki/index.php?title=File:Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG)
Quote from: spooky on September 16, 2013, 12:55:42 PMFrom looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.
As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.
Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.
Quote from: jeffandnicole on September 16, 2013, 03:46:05 PM
Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.
More to the point, if I were going to make a right turn there, I'd be driving across the dot, not around it.
Nonetheless, this setup in theory should work... if everyone yields to each other properly. That's not something you can generally trust American drivers to do, especially when the yield is only implied by pavement marking rather than explicitly stated with a sign. Americans are thickheadded, we need things spelled out for us. :P
Quote from: jeffandnicole on September 16, 2013, 03:46:05 PM
Quote from: english si on September 16, 2013, 01:50:25 PM
Quote from: vdeane on September 15, 2013, 08:19:43 PM
If Quebec can build this thing... http://goo.gl/maps/ofGLZ
That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.sabre-roads.org.uk%2Fwiki%2Fimages%2Fthumb%2F7%2F75%2FTiny_mini_roundabout_1_-_Coppermine_-_4700.JPG%2F799px-Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG&hash=6566b988c12c4a72a52578f8acf351ea734d529b) (http://www.sabre-roads.org.uk/wiki/index.php?title=File:Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG)
Quote from: spooky on September 16, 2013, 12:55:42 PMFrom looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.
As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.
Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.
this is a great candidate for a worst roundabouts around the world thread. Why not just be like those quirky US blokes and put in the ole' 4 way stop gov-na.
Quote from: Indyroads on September 17, 2013, 12:43:45 AM
Quote from: jeffandnicole on September 16, 2013, 03:46:05 PM
Quote from: english si on September 16, 2013, 01:50:25 PM
Quote from: vdeane on September 15, 2013, 08:19:43 PM
If Quebec can build this thing... http://goo.gl/maps/ofGLZ
That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.sabre-roads.org.uk%2Fwiki%2Fimages%2Fthumb%2F7%2F75%2FTiny_mini_roundabout_1_-_Coppermine_-_4700.JPG%2F799px-Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG&hash=6566b988c12c4a72a52578f8acf351ea734d529b) (http://www.sabre-roads.org.uk/wiki/index.php?title=File:Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG)
Quote from: spooky on September 16, 2013, 12:55:42 PMFrom looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.
As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.
Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.
this is a great candidate for a worst roundabouts around the world thread. Why not just be like those quirky US blokes and put in the ole' 4 way stop gov-na.
What for? A mini-roundabout means you yield–you only have to stop if there's someone already there to whom you are required to yield. I like that a lot better than the silly American idea that you might have to stop sometime, so you should be required to stop every time Just In Case. Giving way properly is more important than the dot painted on the asphalt.
Quote from: 1995hoo on September 17, 2013, 09:25:29 AM
Quote from: Indyroads on September 17, 2013, 12:43:45 AM
Quote from: jeffandnicole on September 16, 2013, 03:46:05 PM
Quote from: english si on September 16, 2013, 01:50:25 PM
Quote from: vdeane on September 15, 2013, 08:19:43 PM
If Quebec can build this thing... http://goo.gl/maps/ofGLZ
That's massive. Bricks? Deflection? Pah, all you need is some paint and some signs.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.sabre-roads.org.uk%2Fwiki%2Fimages%2Fthumb%2F7%2F75%2FTiny_mini_roundabout_1_-_Coppermine_-_4700.JPG%2F799px-Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG&hash=6566b988c12c4a72a52578f8acf351ea734d529b) (http://www.sabre-roads.org.uk/wiki/index.php?title=File:Tiny_mini_roundabout_1_-_Coppermine_-_4700.JPG)
Quote from: spooky on September 16, 2013, 12:55:42 PMFrom looking at the satellite imagery, I think you can pretty quickly discount a roundabout without doing a traffic study, especially if they intend to maintain parking.
As has been shown, small roundabouts exist. And there's tons of room there, even maintaining the parking.
Looking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.
this is a great candidate for a worst roundabouts around the world thread. Why not just be like those quirky US blokes and put in the ole' 4 way stop gov-na.
What for? A mini-roundabout means you yield–you only have to stop if there's someone already there to whom you are required to yield. I like that a lot better than the silly American idea that you might have to stop sometime, so you should be required to stop every time Just In Case. Giving way properly is more important than the dot painted on the asphalt.
The problem in this particular example is that the sight lines are very poor. I would've recommended a four-way stop here if both roads have a near-equal amount of traffic due to the very poor sight lines. If the hedges and stone walls were not here, I'd agree that a mini-roundabout is better, but they are, and a four-way stop might be safer. There is no way you can adequately see vehicles, bicycles, or pedestrians at this intersection.
Quote from: spooky on September 16, 2013, 02:16:49 PMI think I can see what you're suggesting, but I don't see how you bring Railroad St into it.
I thought I'd keep it simple, but you can do a double mini-roundabout (https://maps.google.com/?ll=51.676537,-0.607612&spn=0.002924,0.008256&t=m&z=18&layer=c&cbll=51.676758,-0.607596&panoid=TCGSuWJha0hfBLBAO6IUOg&cbp=12,0.92,,0,5.38) if you want to include it.
Quote from: jeffandnicole on September 16, 2013, 03:46:05 PMLooking at the very straight oil line thru the lanes, I don't think traffic is curving to go around the paint in the middle of the roadway.
Yes, it isn't, but mini roundabouts are more a short-hand way of saying "Give Way to Traffic from Right"
Quote from: Indyroads on September 17, 2013, 12:43:45 AMthis is a great candidate for a worst roundabouts around the world thread. Why not just be like those quirky US blokes and put in the ole' 4 way stop gov-na.
Stop signs need special authorisation in the UK, though the visibility here would justify it. However traffic would slow to almost a rolling stop in order to make sure they were giving way to traffic from the right (and right turning traffic from straight on).
4-Way stop is worse as 1) you have to look in both directions (left and right) before entering the junction due to the 'who comes first' priority rather than the 'to the right' priority.
2) you have to stop.
Quote from: 1995hoo on September 17, 2013, 09:25:29 AMWhat for? A mini-roundabout means you yield–you only have to stop if there's someone already there to whom you are required to yield. I like that a lot better than the silly American idea that you might have to stop sometime, so you should be required to stop every time Just In Case. Giving way properly is more important than the dot painted on the asphalt.
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Quote from: Brandon on September 17, 2013, 09:55:06 AMThe problem in this particular example is that the sight lines are very poor. I would've recommended a four-way stop here if both roads have a near-equal amount of traffic due to the very poor sight lines. If the hedges and stone walls were not here, I'd agree that a mini-roundabout is better, but they are, and a four-way stop might be safer. There is no way you can adequately see vehicles, bicycles, or pedestrians at this intersection.
Traffic speeds would be very low - there's no way that stopping would make it safer as even if stopped, you'd still have the same visibility problems.
And the stupid unclear priority rules (and uniqueness of a four-way stop in the UK) would add confusion, which will decrease safety.
Not to mention the boy-who-cried-wolf syndrome that means that the use of STOP over GIVE WAY is very controlled in the UK.
Here's the junction on Street View (https://maps.google.com/maps?ll=56.395807,-3.428421&sspn=0.020973,0.066047&t=m&z=17&layer=c&cbll=56.395006,-3.419068&panoid=JhXBesfBNp3pnGW5W4ZKLg&cbp=12,150.11,,0,11.93).
Quote from: english si on September 17, 2013, 01:29:48 PM
4-Way stop is worse as 1) you have to look in both directions (left and right) before entering the junction due to the 'who comes first' priority rather than the 'to the right' priority.
And the stupid unclear priority rules (and uniqueness of a four-way stop in the UK) would add confusion, which will decrease safety.
Not to mention the boy-who-cried-wolf syndrome that means that the use of STOP over GIVE WAY is very controlled in the UK.
Here's the junction on Street View (https://maps.google.com/maps?ll=56.395807,-3.428421&sspn=0.020973,0.066047&t=m&z=17&layer=c&cbll=56.395006,-3.419068&panoid=JhXBesfBNp3pnGW5W4ZKLg&cbp=12,150.11,,0,11.93).
Even though some idiots don't seem to understand this, there are priority rules for an all-way stop.
1. First-come, first serve.
If you are there first, you go first. If you are there second, you
wait for the first person to go. (Bolded, italicized, and underlined as this is what you do, don't wave someone else!)
2. Priority to the right. If you arrive at the same time as another driver,
the driver to the right goes first, be it you or the other driver. (Who says we don't have priority to the right in the US and Canada. :-P)
3. Straight
then left. Straight movements are supposed to go first, then the left (right in RHD countries) goes behind the straight movement.
Quote from: Brandon on September 17, 2013, 02:01:15 PM
Even though some idiots don't seem to understand this, there are priority rules for an all-way stop.
1. First-come, first serve. If you are there first, you go first. If you are there second, you wait for the first person to go. (Bolded, italicized, and underlined as this is what you do, don't wave someone else!)
2. Priority to the right. If you arrive at the same time as another driver, the driver to the right goes first, be it you or the other driver. (Who says we don't have priority to the right in the US and Canada. :-P)
3. Straight then left. Straight movements are supposed to go first, then the left (right in RHD countries) goes behind the straight movement.
the problem with this is that 1 contradicts 2/3.
if I arrive a split second before someone to my right does, then I have right of way by rule 1, and he has right of way by rule 2, all within the margin of observer error.
Hence the order. In the US/Canada, it's 1, 2, 3. In Europe, it's 2 no matter what.
Quote from: english si on September 17, 2013, 01:29:48 PM
Yes, it isn't, but mini roundabouts are more a short-hand way of saying "Give Way to Traffic from Right"
Given that this is Europe, wouldn't a four-way yield mean the same thing?
Quote from: agentsteel53 on September 17, 2013, 02:07:34 PM
if I arrive a split second before someone to my right does, then I have right of way by rule 1, and he has right of way by rule 2, all within the margin of observer error.
I can't really think of a time when the notion of "Priority to the Right" has noticeably come into a play at any multi-way stop sign intersection I've navigated.
It usually comes down to the perception of who got to the point-of-stop first, even by that "split second". If two cars arrive at
almost the same time - so close it might as well be the same time - rather than anyone defaulting to the "Priority to the Right", it's usually an exercise in social behavior where someone either aggressively feels that they were there first and goes before the other person (though usually in a way where there won't be a collision), or a driver who simply waves (or flashes) the other motorist on first to avoid any conflict.
Maybe it's different some places, but I've found that unless someone were to be at the intersection to irrefutably prove to motorists that cars got there at literally the same time (triggering rules #2 & 3),
someone always got there first.
Quote from: vdeane on September 17, 2013, 09:46:13 PMGiven that this is Europe, wouldn't a four-way yield mean the same thing?
Not in the UK, as there's no default priority to the left (or right) as there is prioritie-a-droit in France, etc. Plus roundabouts in France are prioritie-a-gauche (just as UK ones are give-way-to-right), so a 4-way yield would do the opposite.
Quote from: vdeane on September 15, 2013, 08:19:43 PM
If Quebec can build this thing... http://goo.gl/maps/ofGLZ
Wow, that's only about half a mile from the house of my mother's aunt! I haven't been there in several years, though.
Quote from: Mr_Northside on September 18, 2013, 01:48:21 AMit's usually an exercise in social behavior where someone either aggressively feels that they were there first and goes before the other person (though usually in a way where there won't be a collision), or a driver who simply waves (or flashes) the other motorist on first to avoid any conflict.
if I feel like a situation like this is impending, I purposely slow down enough to have the other driver
clearly get there ahead of me.
it's effective about 85% of the time, which is pretty good given that most people around the residential neighborhood in which I most often encounter four-way stops (basically, "between my work and Home Depot") are morons.
Quote from: vdeane on September 17, 2013, 09:46:13 PMGiven that this is Europe, wouldn't a four-way yield mean the same thing?
No--mini-roundabouts are not the same as stop or yield control (regardless of priority rule) because drivers are required to do whatever is reasonably possible to avoid driving over the painted dot in the middle of the intersection. The dot is there to force traffic entering the intersection to circulate as if it is in a roundabout, and this overrides priority of straight-ahead traffic over turning traffic, priority of traffic approaching from left or right (English Si is correct to say that the UK has no handed-priority rule like the US and continental Europe--this is one thing the British just don't do, like curve advisory speeds), and priority of earlier-arriving traffic, all of which cause problems at US four-way stops.
There are very good reasons four-way stops (or four-way yields in countries where stop control is reserved for unusual visibility limitation) are not used even in countries that don't use mini-roundabouts.
I always felt the yield right rule was a result of the practical implications of the "disputed" portion of the intersection. If the left driver eases forward, the right driver either yields (stays put) or claims the intersection (proceedes). In the second case, the left driver is then required to slow or wait until the right driver, who gets to the disputed quadrant first, clears. As long as no one jack-rabbits, it works quite effectively.
Quote from: J N Winkler on September 18, 2013, 10:51:44 AM
Quote from: vdeane on September 17, 2013, 09:46:13 PMGiven that this is Europe, wouldn't a four-way yield mean the same thing?
No--mini-roundabouts are not the same as stop or yield control (regardless of priority rule) because drivers are required to do whatever is reasonably possible to avoid driving over the painted dot in the middle of the intersection. The dot is there to force traffic entering the intersection to circulate as if it is in a roundabout, and this overrides priority of straight-ahead traffic over turning traffic, priority of traffic approaching from left or right (English Si is correct to say that the UK has no handed-priority rule like the US and continental Europe--this is one thing the British just don't do, like curve advisory speeds), and priority of earlier-arriving traffic, all of which cause problems at US four-way stops.
There are very good reasons four-way stops (or four-way yields in countries where stop control is reserved for unusual visibility limitation) are not used even in countries that don't use mini-roundabouts.
Well, that means we won't see mini-roundabouts in the US! I don't think it's even physically possible for American cars to avoid the dot.
QuoteWell, that means we won't see mini-roundabouts in the US!
Too late. Swing through Manchester, VT on your way back from Burlington for an example.
QuoteI don't think it's even physically possible for American cars to avoid the dot.
It's possible for American CARS (even a minivan). It may not be possible for American DRIVERS.
Mini-roundabouts are everywhere in Seattle and Portland. They're old as shit too.
https://maps.google.com/maps?q=butternut+and+lichen+citrus+heights&ie=UTF-8&hq=&hnear=0x809adf826ac66cd7:0xefdf7c0fc141486b,Butternut+Dr+%26+Lichen+Dr,+Citrus+Heights,+CA+95621&gl=us&ei=63w7UsCzEOeEygHkkYDYCA&ved=0CCkQ8gEwAA (https://maps.google.com/maps?q=butternut+and+lichen+citrus+heights&ie=UTF-8&hq=&hnear=0x809adf826ac66cd7:0xefdf7c0fc141486b,Butternut+Dr+%26+Lichen+Dr,+Citrus+Heights,+CA+95621&gl=us&ei=63w7UsCzEOeEygHkkYDYCA&ved=0CCkQ8gEwAA)
Here's another mini roundabout built into a Citrus Heights intersection.
Not directly "efficiency" related, but just coincidentally, my home town (Madison, Indiana) is looking to add a roundabout at a troublesome intersection;
http://madisoncourier.com/main.asp?SectionID=178&SubSectionID=963&ArticleID=79058 (http://madisoncourier.com/main.asp?SectionID=178&SubSectionID=963&ArticleID=79058)
QuoteAccording to Maurvick, 38 percent of the accidents at the intersection are considered severe accidents, or accidents that involve an injury.
According to Maurvick, that's because the accidents frequently happen at a 90-degree angle. A roundabout, he said, reduces the opportunity for 90-degree collisions. Instead, vehicles are more likely to side swipe one another in a collision.
"You have a much better chance of walking away from a 20 mph sideswipe than a 50 mph T-bone," Maurvick said.
I'm pretty sure this is still a four way stop which too many drivers don't seem to notice until too late.
Fortunately (??), they just built the new hospital a quarter mile away. :-/
Mini-roundabouts, you say?
Circle Drive and Alban Avenue in Tallahassee (https://maps.google.com/maps?q=tallahassee,+fl&hl=en&ll=30.43043,-84.264097&spn=0.000384,0.00071&oe=utf-8&client=firefox-a&hnear=Tallahassee,+Leon,+Florida&t=k&z=21&layer=c&cbll=30.43043,-84.264225&panoid=MAC3QHimUgo0rsqk88lrMA&cbp=12,10.66,,0,18.88) - no driving over that "dot". And it used to be just a little concrete pillar in the middle of the intersection!
Or this one (https://maps.google.com/maps?q=tallahassee,+fl&hl=en&ll=30.430478,-84.266349&spn=0.000387,0.00071&oe=utf-8&client=firefox-a&hnear=Tallahassee,+Leon,+Florida&t=h&z=21&layer=c&cbll=30.430478,-84.266477&panoid=5Uy_MDAK-DA0pTbYcwJ2qg&cbp=12,277.24,,0,8.63), one block to the west at Circle and Seminole Drive.
this begs the question... How many people just ignore the glorified planter island or painted dot in the center of the intersection and just make a left turn (on the wrong side of the island) anyway because they are lazy or just don't care? And would a cop really make a big deal of it?
During my 7 years in Australia I got pretty familiar with them.
Small roundabouts that replace 4-way stops: I loved them. If the thing is empty, you just plow right around it without stopping, which is a big plus.
However, I hated the large multi-lane setups, especially when there were multiple spokes. There were parts of Melbourne that had maybe five or six points coming out with two and even three lanes in the roundabout, and I found those to be quite intimidating.
So I've tended to form the opinion that the one-lane variety is superior, but the multi-lane variety is not.