Am I the only person who hates going through a roundabout? What I hate even more are the two-laned roundabouts. I first saw one in the 90s when one was constructed near the Jackson International Airport. It's a one-lane roundabout, so I can at least deal with that one. Since then, one was constructed on Highland Colony Parkway north of town and several have been built in the Jackson State University area (all two-lane roundabouts). The ones near the JSU area are not heavily traveled (at least when schools not in session), but traffic volume has been increasing on HCP with all the suburban development going on there. I almost got into an accident once with somebody not being aware how to navigate through a roundabout.
I love roundabouts. I wish there were more roundabouts. I wish idiot Americans would stop complaining about roundabouts and actually take the time to learn how to properly navigate them.
And as for this near accident, was it you or the other guy that was in the roundabout? did someone not give way to the person inside? what happened?
The two most important things when approaching a roundabout:
1) Position your vehicle in the appropriate lane before approaching the roundabout, so exiting is easier and you don't change lanes inside (which is highly discouraged and problematic for other drivers).
2) Entering traffic always yields to traffic already inside the circulatory roadway.
Roundabouts really aren't that hard to master once you grasp these concepts. They are much more efficient than multi-way stops at low to moderate volume intersections. Two-lane roundabouts aren't all that bad, either. More recent roundabouts are designed with better signage and striping/markings such that it is much easier to determine lane positioning to easily navigate the roundabout. Now three-lane roundabouts, even with excellent signing and striping...that's pushing it!
3 lanes can be done fairly easily. Roundabouts on motorway junctions in Britain sometimes will have 3 lanes, striped and marked well from the beginning, telling you to stay in lane, and you eventually just end up on the road you want.
The fact that roundabouts are still fairly new to the U.S. (first ones being installed in Las Vegas in the early 1990s) is a major reason why so many people seem to have issues with them. Until more drivers become accustomed to driving roundabouts, I don't think three-lane roundabouts will see widespread use in the states.
There are some (partial) three-lane roundabouts in Nevada. I don't think they're too bad, but experience shows that some drivers just don't grasp the concept and have trouble negotiating them.
I only hate roundabouts when they replace traffic signals (honestly, who didn't see this coming? :D ). Other than that, I am so-so about them.
I love Roundabout (the song by Yes). I hate roundabouts! They serve no purpose and are nothing but a waste of taxpayers money! There are 2 in this area that I know of. One is in front of a retirement home along a residential drive that has no traffic whatsoever (probably 2-300 cars/day). Absolutely no reason for a roundabout, traffic light or even a stop sign. The other one replaced a 4-way stop where traffic would back up for a half mile or so in every direction. They built the roundabout and traffic still backs up for a half mile or so in every direction! Quit wasting our money on these unnecessary atrocities!
Wait, so how do multi-lane roundabouts work, anyway? I get single-lane ones, of course, but how do the two-lane ones work? If you're in the left lane on a spoke road, do you have to wait for both lanes of the circulatory to clear? And then wait for the right-hand lane to clear before exiting the roundabout? :hmmm: Sounds dangerous and/or prone to long waits!
Quote from: Scott5114 on September 18, 2009, 08:54:56 AM
Wait, so how do multi-lane roundabouts work, anyway?
Not very well! :-D
Quote from: Terry Shea on September 18, 2009, 08:59:23 AM
Quote from: Scott5114 on September 18, 2009, 08:54:56 AM
Wait, so how do multi-lane roundabouts work, anyway?
Not very well! :-D
Not exactly the response I was looking for, Terry :happy:
The problem with roundabouts can be illustrated by a trip to your local Secretary of State/DMV/whatever they call it in your state. While you're there, take a look at the luddites that inhabit the long lines, and you'll have your answer.
Quote from: golden eagle on September 18, 2009, 12:30:36 AM
Am I the only person who hates going through a roundabout?
No, I dislike them immensely.
I like roundabouts, myself. I'd like to see more. Currently, GDOT will only build single lane roundabouts, but they're open to the idea of multi-lane roundabouts; however, multi-lane roundabouts must be approved by the chief engineer.
Single lane roundabouts (ADT): less than 20,000 vpd
Multi-lane roundabouts (ADT): less than 40,000 vpd
Be well,
Bryant
Multi-lane roundabouts: you choose your position on the approach roadway according to the exit you intend to take (moving further to the left the more of the circle you plan to negotiate) and, once in the circulatory carriageway, you work your way to the right as you approach the exit you want to take. It is actually very simple to do and many multilane roundabouts now have spiral markings which help you maintain optimum lane position as you go through.
When you enter a multilane roundabout, you have to yield to all lanes in the circulatory carriageway. You should do this when you turn into a multilane road too--it is not defensive driving to assume that approaching traffic won't change into your lane just as you start the turning maneuver.
QuoteWait, so how do multi-lane roundabouts work, anyway? I get single-lane ones, of course, but how do the two-lane ones work? If you're in the left lane on a spoke road, do you have to wait for both lanes of the circulatory to clear? And then wait for the right-hand lane to clear before exiting the roundabout? Sounds dangerous and/or prone to long waits!
No it's just like turning from a street with 2 right turn lanes. If the outside lane is clear but the inside is taken, then the outside lane can turn in white the inside lane waits. If the outside lane is occupied but the inside clear everyone will wait until it's clear.
WHAT IS THE BIG DEAL with people not liking traffic circles?
Quote from: Annunciation70130 on September 18, 2009, 12:20:36 PM
QuoteWait, so how do multi-lane roundabouts work, anyway? I get single-lane ones, of course, but how do the two-lane ones work? If you're in the left lane on a spoke road, do you have to wait for both lanes of the circulatory to clear? And then wait for the right-hand lane to clear before exiting the roundabout? Sounds dangerous and/or prone to long waits!
No it's just like turning from a street with 2 right turn lanes. If the outside lane is clear but the inside is taken, then the outside lane can turn in white the inside lane waits. If the outside lane is occupied but the inside clear everyone will wait until it's clear.
WHAT IS THE BIG DEAL with people not liking traffic circles?
Because I don't like accidents, traffic jams and wasting tax payers money. I don't know, maybe they make sense in some areas but the ones I've seen do nothing to alleviate traffic tie-ups, confuse the drivers causing more accidents and are nothing but a big waste of money! Put up a traffic signal if the traffic volume warrants it but get rid of these stupid merry-go-rounds. A lot of drivers are dizzy enough w/o them.
I prefer the turn right then U-Turn thing myself, but Roundabouts are not as bad as people make them out to be. A useless roundabout doesn't waste the amount of money that a useless signal interchange would. It's a simple process: Yield, Go Yield, Go Yield Go.
I'm nowhere nere and advocate of roundabouts, but i don't think they get a fair shot.
Quote from: Terry Shea on September 18, 2009, 01:50:01 PM
I don't know, maybe they make sense in some areas but the ones I've seen do nothing to alleviate traffic tie-ups, confuse the drivers causing more accidents and are nothing but a big waste of money!
Do you have a cite that supports this? I've seen some DOT statements that say roundabouts generally
improve safety. I'd be interested to see how the costs and benefits of roundabouts work out as well.
I'd much prefer a roundabout to a four-way stop - or even a stop sign period. If there is no traffic around, you can waltz right through - while a 4 way stop - you HAVE to stop - even if no one's around.
I personally love roundabouts. Once people get used to driving in them, which does take some time, mind you, I've noticed that the amount of griping about them tends to go down, generally.
Roundabouts have really begun to spring up here in Michigan in recent years, and I know of many more planned. The same thing is true in New York State, where I believe NY 590 north of NY 104 in Irondequoit, NY is being reconstructed into a succession of a few roundabouts up to its current Northern Terminus by Sea Breeze...although it looks like when the work is done, it will be truncated to the southernmost of those roundabouts.
Quote from: Terry Shea on September 18, 2009, 08:52:07 AM
I love Roundabout (the song by Yes). I hate roundabouts!
Ditto here for the most part. Yes is my favorite band :sombrero: and while I've grown to accept some roundabouts, I don't think they're the cure-all that some tout them to be. My biggest pet peeve with them is when people don't use their turn indicators, as required by law (at least here in Oregon). Because of that, it's hard to tell just where people are exiting the roundabout, and it ends up functioning like a really convoluted 4-way stop.
Case in point of roundabouts that don't work--the two rural roundabouts that Washington County, Oregon's Department of Land Use and Transportation (DLUT) installed in 2003 on
NW Verboort Road (http://maps.google.com/maps?hl=en&client=firefox-a&q=NW+Verboort+Rd,+Forest+Grove,+Washington,+Oregon+97116&ie=UTF8&cd=1&geocode=FYIItwId6N2p-A&split=0&sll=37.0625,-95.677068&sspn=23.875,57.630033&ll=45.551428,-123.069556&spn=0.006581,0.01929&z=16), a major arterial north of Forest Grove that forms part of a link between OR-47 and US-26. The
accident statistics (http://www.co.washington.or.us/LUT/Divisions/Operations/loader.cfm?csModule=security/getfile&pageid=38488) released by the county to the Rural Roads Committee in 2008 showed negligible improvements.
-Alex
I don't understand what all the roundabout hate is either. I must admit that I don't get multi-lane roundabouts. Do you have to change lanes in the circle? Can that be safely done? There's one coming to Rochester soon (NY 590/Titus Ave) and while it will only be two lanes on one side (the other is single lane) I imagine it will be very difficult from drivers to go between Titus Ave and Titus Ave Ext.
@DanTheMan: the signage for NY 590's truncation at Titus is already up. Haven't been up there since mid-August so I don't know if traffic is using that side of the road yet or not.
@Tarkus: that problem could be solved by having police give out tickets to drivers that don't use their signals. It would work fine if people just drove properly!
Addressing multiple points relating to negotiating multi-lane roundabouts...
Quote from: Scott5114
Wait, so how do multi-lane roundabouts work, anyway? I get single-lane ones, of course, but how do the two-lane ones work? If you're in the left lane on a spoke road, do you have to wait for both lanes of the circulatory to clear? And then wait for the right-hand lane to clear before exiting the roundabout? Hmm. Sounds dangerous and/or prone to long waits!
Quote from: J N Winkler
Multi-lane roundabouts: you choose your position on the approach roadway according to the exit you intend to take (moving further to the left the more of the circle you plan to negotiate) and, once in the circulatory carriageway, you work your way to the right as you approach the exit you want to take. It is actually very simple to do and many multilane roundabouts now have spiral markings which help you maintain optimum lane position as you go through.
Quote from: deanej
I must admit that I don't get multi-lane roundabouts. Do you have to change lanes in the circle? Can that be safely done?
With most newer roundabouts, there is significant striping in the circulatory roadway itself that guides the user to the appropriate roundabout exit. It should be noted that you don't always work your way to the right within the roundabout itself--especially in cases where the number of approach lanes equals the number of exit lanes. In cases where you do work your way to the right to exit, you don't change lanes per se, but the striping guides you outward at an appropriate point so as to not conflict with other circulating traffic. If you happen to be using an inside lane, striping within the circulatory roadway directs traffic on your right to exit at points which do not conflict with the exits prescribed to your lane.
It's kinda tough to explain how multi-lane roundabouts work using words only, so here's a visual aid for those interested: The proposed MUTCD has 15 figures depicting lane striping at various types of roundabouts (the current version only has two figures, which aren't nearly as illustrative). Go to the Proposed Amendments to the MUTCD page (http://mutcd.fhwa.dot.gov/resources/proposed_amend/index.htm) and click on the "Proposed Figures" PDF link. Figures 3C-4 through 3C-17 (pages 233-248 of the PDF) show pavement lane markings for single- and multi-lane roundabouts for a variety of entry and exit conditions (including connected roundabouts at freeway interchanges). Certain figures show how the striping guides a driver from the inner to an outer lane to make an exit, in conditions where the number of lanes are not equal on all approaches or throughout the entire circle.
Several state/local agencies have also published informative guides to educate drivers about negotiating roundabouts (here's an example from Nevada DOT (http://www.nevadadot.com/safety/pdfs/RBbrochure.pdf)).
Quote from: Annunciation70130
No it's just like turning from a street with 2 right turn lanes. If the outside lane is clear but the inside is taken, then the outside lane can turn in white the inside lane waits. If the outside lane is occupied but the inside clear everyone will wait until it's clear.
WHAT IS THE BIG DEAL with people not liking traffic circles?
Not the case at all. The way roundabouts are designed, traffic within the circulatory roadway does not have to yield to any other drivers, including those in other lanes of the roundabout. Traffic within the circulatory roadway should not stop at any time. The situation you're describing sounds more akin to a traffic circle than a roundabout.
The term "traffic circle" is not synonymous with the term "roundabout".
QuoteNot the case at all. The way roundabouts are designed, traffic within the circulatory roadway does not have to yield to any other drivers, including those in other lanes of the roundabout. Traffic within the circulatory roadway should not stop at any time. The situation you're describing sounds more akin to a traffic circle than a roundabout.
The term "traffic circle" is not synonymous with the term "roundabout".
Where did I say anywhere that traffic in the circle yields? I was referring to traffic entering the circle, not leaving it. You can't turn into and inside lane from an inside lane if the lane outside of the one you are turning into is occupied and that's pretty much the case.
My city has both roundabouts and traffic circles and people hate them all the same.
Wisconsin has had roundabout fever recently (http://www.dot.wisconsin.gov/safety/motorist/roaddesign/roundabout-works.htm), which is both a good thing and a baaaaad thing.
Good roundabouts:
The intersection in the middle (http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=fitchburg,+wi&sll=37.0625,-95.677068&sspn=33.435463,77.871094&ie=UTF8&ll=43.020133,-89.430245&spn=0.003765,0.009506&t=h&z=17&iwloc=A) has a roundabout, but this is a very light intersection and is more decorative than functional. There's more landscaping there now than Street View shows and I've never had a problem with it.
This one is a bit (http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=fitchburg,+wi&sll=43.020423,-89.430739&sspn=0.003765,0.009506&g=fitchburg,+wi&ie=UTF8&ll=43.041216,-89.35465&spn=0.007528,0.019011&t=h&z=16&layer=c&cbll=43.041114,-89.35448&panoid=S_fgjcMh_VIfqOPJi6YUWg&cbp=12,177.98,,0,5.3%5B/url) more awkward. It popped up in the past year and people are still getting used to it but there are plenty of signs directing traffic. Why do I think this one is good? There's a gas station that is only accessible from southbound traffic (i.e., off the freeway) by coming up to the intersection and making a U-turn. The road is too busy otherwise to have a direct access to Royal Ave like Google Maps currently shows. Making a U-turn here feels so much safer and efficient than having to wait for a sharp U-turn at a signal. Bravo.
Bad roundabouts:
Hoo boy. (http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=fitchburg,+wi&sll=43.020423,-89.430739&sspn=0.003765,0.009506&g=fitchburg,+wi&ie=UTF8&ll=42.96948,-90.112775&spn=0.007536,0.019011&t=h&z=16) So last year about this time, WisDOT closed US 18 just east of Dodgeville, WI, directing traffic to South WI-23 and I never bothered looking up why. Never went that way often enough to care. When they finally opened up later that fall, there was a 2-lane roundabout right in the middle of that image, at Bennett Rd. Signs direct traffic to slow down to 25 MPH and go go go go carefully. Problem is, this was the Dodgeville Expressway and the speed limit west and east of the intersection is 55 MPH. Instead of a triggered-only stoplight, everyone has to slow down... then speed back up again. It's infuriating.
There's more: Here is a PDF (http://www.dot.wisconsin.gov/projects/docs/us12newsspring2006.pdf) of the latest roundabouts, three of them on US-12 between Lake Delton and Baraboo. PHANTOM EDIT: Upon closer inspection, they mentioned using three interchanges meaning that the exits will utilize roundabouts but traffic will flow uninterrupted. Whew. Still, the road carries a lot of casino traffic and tourist traffic, so those trying to exit the freeway may be a bit confused. It's still silly and a bad precedent.
Quote from: Annunciation70130 on September 18, 2009, 05:06:23 PM
Where did I say anywhere that traffic in the circle yields? I was referring to traffic entering the circle, not leaving it. You can't turn into and inside lane from an inside lane if the lane outside of the one you are turning into is occupied and that's pretty much the case.
I misinterpreted your first response...my apologies.
However, if I'm understanding what you wrote, the first part of your comment isn't always correct. Entering vehicles should to yield to all vehicles in any lane of the circulatory roadway--especially since all roundabouts are not marked the same, and few drivers actually signal their intent to exit a roundabout.
Say a driver is heading northbound towards a 4-leg roundabout approaching from the outside lane. When that driver reaches the yield line, there's a car coming in the inner circulating lane at the same time. If the driver in the inner circulating lane wants to exit on the east leg of the roundabout, the northbound driver cannot enter simultaneously, because their paths will cross at the eastbound exit (resulting in a sideswipe collision). The northbound driver has to wait for the circulating vehicle to clear the conflict point before entering the roundabout.
Quote from: rawr apples on September 18, 2009, 02:03:26 AM
I love roundabouts. I wish there were more roundabouts. I wish idiot Americans would stop complaining about roundabouts and actually take the time to learn how to properly navigate them.
And as for this near accident, was it you or the other guy that was in the roundabout? did someone not give way to the person inside? what happened?
I was trying to go north and was in the right lane, the other driver was in the left lane trying to go east.
Quote from: roadfro on September 18, 2009, 04:23:00 PM
The term "traffic circle" is not synonymous with the term "roundabout".
To me it is... :banghead:
Quote from: Tarkus on September 18, 2009, 03:53:37 PM
Case in point of roundabouts that don't work--the two rural roundabouts that Washington County, Oregon's Department of Land Use and Transportation (DLUT) installed in 2003 on NW Verboort Road (http://maps.google.com/maps?hl=en&client=firefox-a&q=NW+Verboort+Rd,+Forest+Grove,+Washington,+Oregon+97116&ie=UTF8&cd=1&geocode=FYIItwId6N2p-A&split=0&sll=37.0625,-95.677068&sspn=23.875,57.630033&ll=45.551428,-123.069556&spn=0.006581,0.01929&z=16), a major arterial north of Forest Grove that forms part of a link between OR-47 and US-26. The accident statistics (http://www.co.washington.or.us/LUT/Divisions/Operations/loader.cfm?csModule=security/getfile&pageid=38488) released by the county to the Rural Roads Committee in 2008 showed negligible improvements.
Were those two roundabouts originally proposed to be multilane ones? The markings seem to indicate such.
Quote from: wandering drive on September 18, 2009, 06:04:17 PM
The intersection in the middle (http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=fitchburg,+wi&sll=37.0625,-95.677068&sspn=33.435463,77.871094&ie=UTF8&ll=43.020133,-89.430245&spn=0.003765,0.009506&t=h&z=17&iwloc=A) has a roundabout, but this is a very light intersection and is more decorative than functional. There's more landscaping there now than Street View shows and I've never had a problem with it.
Interesting. A 2-way stop with a roundabout.
Here they installed recently the first roundabout in Hampton Roads that I am aware of on a public roadway, but it is pathetic. All they did was take an existing 4-way intersection with a 2-way stop and put a small circular plastic curb in the middle, and remove the stop signs. It is rather pointless as there is not much traffic and it is ineffective at slowing down traffic, which was its purpose (it was installed about 500 feet before where Beach Rd. in Hampton ends right at the edge of the Chesapeake Bay--come flying through there and prepare to get wet). And so far it seems to be a waste of money in most regards because, to prevent people from flying through it, they installed those folding plastic pole things along the shoulder line, which are all replaced about every 2 weeks because they get repeatedly flattened.
Quote from: deathtopumpkins on September 18, 2009, 08:41:03 PM
Quote from: wandering drive on September 18, 2009, 06:04:17 PM
The intersection in the middle (http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=fitchburg,+wi&sll=37.0625,-95.677068&sspn=33.435463,77.871094&ie=UTF8&ll=43.020133,-89.430245&spn=0.003765,0.009506&t=h&z=17&iwloc=A) has a roundabout, but this is a very light intersection and is more decorative than functional. There's more landscaping there now than Street View shows and I've never had a problem with it.
Interesting. A 2-way stop with a roundabout.
That sat image is likely taken before the roundabout was installed.
Quote from: roadfro on September 18, 2009, 08:02:35 PM
However, if I'm understanding what you wrote, the first part of your comment isn't always correct. Entering vehicles should to yield to all vehicles in any lane of the circulatory roadway--especially since all roundabouts are not marked the same, and few drivers actually signal their intent to exit a roundabout.
You're right as far safety/legal standpoint, but in the city a lot of times the defacto rule is "get in where ya fit". Sit and wait for all lanes to clear and you'll probably never get in and in the process be cursed out, have something thrown at you, or in rare cases shot at.
I know it's dangerous, but it is what it is.
Quote from: Master son on September 18, 2009, 09:23:29 PM
Quote from: deathtopumpkins on September 18, 2009, 08:41:03 PM
Quote from: wandering drive on September 18, 2009, 06:04:17 PM
The intersection in the middle (http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=fitchburg,+wi&sll=37.0625,-95.677068&sspn=33.435463,77.871094&ie=UTF8&ll=43.020133,-89.430245&spn=0.003765,0.009506&t=h&z=17&iwloc=A) has a roundabout, but this is a very light intersection and is more decorative than functional. There's more landscaping there now than Street View shows and I've never had a problem with it.
Interesting. A 2-way stop with a roundabout.
That sat image is likely taken before the roundabout was installed.
The Street View clearly shows stop signs on two approaches :confused:
Quote from: Master son on September 18, 2009, 09:23:29 PM
Quote from: deathtopumpkins on September 18, 2009, 08:41:03 PM
Quote from: wandering drive on September 18, 2009, 06:04:17 PM
The intersection in the middle (http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=fitchburg,+wi&sll=37.0625,-95.677068&sspn=33.435463,77.871094&ie=UTF8&ll=43.020133,-89.430245&spn=0.003765,0.009506&t=h&z=17&iwloc=A) has a roundabout, but this is a very light intersection and is more decorative than functional. There's more landscaping there now than Street View shows and I've never had a problem with it.
Interesting. A 2-way stop with a roundabout.
That sat image is likely taken before the roundabout was installed.
I was referring to the streetview. ;-) The satellite view doesn't show the roundabout at all.
Quote from: deathtopumpkins on September 19, 2009, 10:49:40 AM
QuoteThat sat image is likely taken before the roundabout was installed.
I was referring to the streetview. ;-) The satellite view doesn't show the roundabout at all.
Ah - forgot to look down - doesn't look like a true roundabout for sure. if anything that was hap-hazardly put together by the local street department :pan:
The term traffic circle is deprecated in relation to circular intersections which operate to a yield-on-entry rule because it is also used to refer to circular intersections where traffic in the circle does have to yield to entering traffic, like at the Arc de Triomphe in Paris.
There are also presentational advantages in differentiating between roundabouts and traffic calming circles. Roundabouts are specialized to handle balanced traffic flows more efficiently and safely, with shorter queues and less waiting time, in comparison to traffic signals. In fact, the standard recommendation nowadays (in many jurisdictions) is to use traffic signals only in constrained locations, to handle severely unbalanced flows, or when the overall volumes would cause a roundabout to "lock up" but system considerations militate against grade separation. Traffic calming circles are a different animal altogether--they usually try to reduce traffic speeds in residential neighborhoods by leaving the existing curb returns unrevised while replacing part of the circulatory area in the intersection with an island.
In general, I believe it is a mistake to introduce roundabouts and traffic calming circles at the same time in a community which is naïve to both, and in general to design roundabouts with crossfall in the circulatory carriageway so steep that they come across more as traffic calming devices than as a different form of intersection control.
I think a reason that Americans and roundabouts may not get along so well is because Americans are loathe to yield to anyone. Or is that just Oklahomans (somehow I doubt that). I doubt most people around here would yield to their own grandmother!
Quote from: J N Winkler on September 19, 2009, 12:22:45 PM
The term traffic circle is deprecated in relation to circular intersections which operate to a yield-on-entry rule because it is also used to refer to circular intersections where traffic in the circle does have to yield to entering traffic, like at the Arc de Triomphe in Paris.
There are also presentational advantages in differentiating between roundabouts and traffic calming circles. Roundabouts are specialized to handle balanced traffic flows more efficiently and safely, with shorter queues and less waiting time, in comparison to traffic signals. In fact, the standard recommendation nowadays (in many jurisdictions) is to use traffic signals only in constrained locations, to handle severely unbalanced flows, or when the overall volumes would cause a roundabout to "lock up" but system considerations militate against grade separation. Traffic calming circles are a different animal altogether--they usually try to reduce traffic speeds in residential neighborhoods by leaving the existing curb returns unrevised while replacing part of the circulatory area in the intersection with an island.
In general, I believe it is a mistake to introduce roundabouts and traffic calming circles at the same time in a community which is naïve to both, and in general to design roundabouts with crossfall in the circulatory carriageway so steep that they come across more as traffic calming devices than as a different form of intersection control.
Spot-on descriptions.
"Traffic calming circles", as used in residential neighborhoods, can be a great way to reduce speeds--I much prefer these over unwarranted two-way or four-way stop signs. I've also heard the term "mini roundabout" used professionally to describe these.
My understanding is that traffic circles are being gradually phased out in many areas, in favor of roundabouts or other controls. In my personal opinion, it would be a mistake to introduce traffic circles
anywhere in the U.S. that doesn't already have them...and it's better to just not construct new ones at all. Seeing some of the circles in Washington DC in action a few years ago really made my head spin--definitely some complex signal timing involved to make sure those don't jam up.
I believe the cross slope of roundabouts is generally designed to be around 2%, which is the standard crossfall of a typical roadway.
Quote from: Scott5114 on September 18, 2009, 02:36:27 PM
Quote from: Terry Shea on September 18, 2009, 01:50:01 PM
I don't know, maybe they make sense in some areas but the ones I've seen do nothing to alleviate traffic tie-ups, confuse the drivers causing more accidents and are nothing but a big waste of money!
Do you have a cite that supports this? I've seen some DOT statements that say roundabouts generally improve safety. I'd be interested to see how the costs and benefits of roundabouts work out as well.
Well the only experience I've had with them is the 2 that I mentioned previously. The one that receives too much traffic is the one at the intersection of 3 Mile RD and Dean Lake Ave in Grand Rapids Twp. Traffic gets backed up as far as the eye can see in all directions during rush hour. It did when it was a 4-way stop and it still does now.
The other one is in front of a retirement home on Pfeiffer Woods Dr in Kentwood. It's not even at the main entrance to the home but at a service drive! And I'm betting that large service vehicles making deliveries are going to have trouble negotiating the tight sharp turns. (Kentwood has also been turning their busy streets into boulevards with Michigan left turns and they didn't design most of them with enough room for a semi to negotiate the left turn.) Like I said there is absolutely no reason for a roundabout, traffic signal or stop sign here because there is absolutely no traffic on this road.
Both of these projects were a total waste of money. The one doesn't do the job it was designed to do because traffic is still log jammed and the other serves no purpose whatsoever, accept for making it difficult for delivery trucks to enter the service drive.