Rotaries, Roundabouts, and Traffic Circles

[Subdude]

In the UK most roundabouts at major intersections have traffic signals to control the flow of traffic into the circle. There are occasional backups, but overall it seems to work fairly well. The confusing thing is being in the circle and having to maneuver to the correct lane to exit where you want, but at least traffic slows naturally as it enters the circle.

[CDeb]

It seems like a really good place for roundabouts are places like neighborhoods. When you're in a huge neighborhood, it can be a pain to stop at a million signs if you're heading towards the back.

So what kind of intersections would yall who seem to know more about this, suggest these things go if they were to implement them (which I think they are. I was on some city website and it had those listed as future projects)? Intersections that have mid-level congestion to lower level? Seems like yall think where there is a ton of congestion would be a bad place. Although in Paris at the Arc de Triumph, I believe that one has signal lights to help control flow, and although there were a ton of cars on there, it seemed to work pretty well, even though I was on foot and not in an automobile.

Personally, I think they are better suited for more suburban/rural settings, where traffic intensity is moderate, there are fewer pedestrians, and development is less dense. In those locales, they should be considered at unsignalized intersections before a signal is considered (although a signal may still be a better option for many intersections). While they usually cost more initially, they have essentially zero maintenance requirements and have an excellent safety record.

[musicman]

That's because the traffic circle in the photo is a traffic circle and not a roundabout. It isn't using yield at entry operation, hence the lockup.

concur

[lockmat]

concur

So what's the difference between a roundabout and a circle?

[CDeb]

So what's the difference between a roundabout and a circle?

There are three main differences:

1) The biggest is the operation. In traffic circles, the circulating traffic yields to entering traffic. In a roundabout, the entering traffic yields to the circulating traffic.

2) Size. Traffic circles are generally larger than roundabouts, thus having higher operating speeds and no safety advantage.

3) Flaring at entry. Roundabouts are more geometrically designed to slow enering vehicles, mainly by "flaring" the entry (i.e. adding curvature).

[Subdude]

Hmm. I thought they were just different names for the same thing.

Would that even work if the circulating traffic yields to entering traffic?

I have seen "mini-roundabouts" which are basically a dot painted in the street at an intersection. In these it seems strange having to yield to turning traffic when you are going straight.

[CDeb]

Hmm. I thought they were just different names for the same thing.

Common misconception. I believe that most people's aversion to roundabouts is due to their equating them with an awful traffic circle that they've experienced in the past.

And, as I've said before, roundabouts aren't a panacea. There are definitely some poorly-designed ones out there, and some installed at inappropriate locations.

[plumber2]

There was also another traffic circle on N. Wayside at Clinton Drive. Our high school student driving instructor made all of us drive this one and the one on Kelley St. (North Loop) at the Eastex Freeway. They were both pretty scary intersections for a 15 year old back in 1970. The driving instructor was a former marine sargent who was constantly barking at us to stay in our lane, keep your eyes on the road, to use our turn signals and so forth. Some of the girls would start to cry which really pissed him off even more. We all suvived though but those two traffic circles obviously didn't.

[Subdude]

I've seen photos of that one.

I guess your opinion depends on what you're used to. As it happens, I had a discussion about roundabouts last night with an English guy. He thought the worst thing about his experience driving in the US was the number of stop signs. He found it incredibly frustrating to go block after block starting and stopping, while with roundabouts you can frequently cover quite a distance without having to stopp. He also thought the system of stop signs and traffic signals was incredibly wasteful of fuel.

[Subdude]

Interesting stats on roundabouts from an NYTimes column.

Q. The United States has very few traffic circles, or roundabouts, as they are known in the United Kingdom. Are there traffic flow benefits to using traffic circles, assuming we could somehow teach the population how they should be properly entered and exited?

[CoolBuddy06]

I strongly oppose the use of unregulated traffic circles for arterial streets, as congestion in one direction can obstruct traffic going in the other three directions. The most problematic thoroughfares, such as SH6, need overpasses. However, traffic circles in residential neighbourhoods would be greatly beneficial, as an alternative to frequent stop signs.

Well said. My native country uses rotary style a lot, even on busy streets. Guess what? Traffic is nerve-racking-everyday of the week.

[Texas Wahoo]

I just got back from Cairns, Australia. They have a ton of giant traffic circles. Traffic definitely seems to flow faster and it cuts down on commute times, but as the original post says, it is a nightmare for pedestrians. You can't tell which cars are going to be coming your way and during rush hour the cars come constantly.

[ssullivan]

At busy traffic circles in large cities in Europe, there are usually pedestrian tunnels or pedestrian signals to allow pedestrians to navigate the intersection safely. Several of these also exist with at circles in Washington DC.

I'm all for increased use of yield-entry modern traffic circles in this country. Several states are using them more often, such as Colorado, and they work quite well. There's one in Grand Junction I drive through on a daily basis when I'm there for work, and it is much easier than dealing with a traffic light, especially since my morning commute always involves a left turn at this particular intersection.

The idea that people would find it difficult to go slowly around a small circle with other cars raises questions about whether those people should be operating heavy machinery to begin with.

This is so true! Of course these idiots who can't understand a roundabout are the same ones who can't understand a no left turn sign on Main St. in Houston.

[Ross]

Doha, Qatar is removeing most of the roundabouts, or putting signals on the ones where streets enter at odd angles. Removing the roundabouts has helped traffic flow tremendously, and prevented many accidents caused by drivers not following the rules on how to enter and leave roundabouts. Removal is pretty easy, as there's plent of space to put in multiple left turn lanes while maintaining the same number of through lanes.

[The Voice of University Oaks]

Doha, Qatar is removeing most of the roundabouts, or putting signals on the ones where streets enter at odd angles. Removing the roundabouts has helped traffic flow tremendously, and prevented many accidents caused by drivers not following the rules on how to enter and leave roundabouts. Removal is pretty easy, as there's plent of space to put in multiple left turn lanes while maintaining the same number of through lanes.

Dubai is also replacing congested roundabouts with standard four-way intersections. For example, the roundabout at Sheikh Kalifa bin Zayed Street and Bin Al Waleed Street in front of the Burjuman: it might have been a great idea fifteen years ago, when the number of vehicles in Dubai was a fraction of what they are today, but today that intersection is an absolute disaster. Once construction on the metro station at that location is complete, the roundabout will be replaced with a conventional intersection.

Roundabouts that haven't yet become congested, on the other hand, seem to work well.

[Subdude]

I agree. From what I've seen there are almost never roundabouts in congested city where there is a lot of pedestrian traffic. In pedestrian areas of cities it seems better to have signalized intersections to allow safe pedestrian crossing. On the other hand, small roundabouts in low traffic residential neighborhoods can be OK for pedestrians, since they are about the same size as an intersection with a stop sign (just paint a white dot in the middle).

What can be a challenge is riding a bicycle through a circle. This is because bikers generally keep to the side, and in a roundabout drivers will assume you plan to turn our of the circle and cut you off. I had several near-misses from this happening until a bike-commuting colleague pointed out that the trick was to cut closer into the center of the circle which will force cars to yield. I do that now and it works just fine. So now you know.

[dbigtex56]

What can be a challenge is riding a bicycle through a circle. This is because bikers generally keep to the side, and in a roundabout drivers will assume you plan to turn our of the circle and cut you off. I had several near-misses from this happening until a bike-commuting colleague pointed out that the trick was to cut closer into the center of the circle which will force cars to yield. I do that now and it works just fine. So now you know.

What you're saying makes sense.

Sense doesn't seem to be overrepresented among Houston drivers. I fear that nothing less than bicycles equipped with mine-like explosives will 'force' anyone to yield, locally.

[Subdude]

Learning to love the roundabout!

Why American drivers should learn to love the roundabout.

By Tom VanderbiltPosted Monday, July 20, 2009, at 6:54 AM ET

Here is a narrative that has been playing out over the last several years in any number of American towns: Traffic engineers notice that a particular intersection has a crash problem or is moving traffic inefficiently. After a period of study, the engineers propose a roundabout. The engineers, armed with drawings and PowerPoint slides, visit a community meeting. They try to explain the benefits of their proposed design in clear language, though they may occasionally drop phrases like entry path overlap or inscribed circle diameter. Townspeople raise concerns. Roundabouts are not safe, they say. They are confusing. They are bad for pedestrians. They will hurt local businesses. They are more expensive than traditional solutions. The local newspaper reports this, adding some man-in-the-street comments from "area drivers," who profess not to like roundabouts, even making dark references to "circles of death." Then, the roundabout is built, the safety record improves, traffic congestion doesn't seem any worse than before, and the complaints begin to fade faster than white thermoplastic lane markings in the heat of summer.

According to best estimates, the United States is now home to about 2,000 "modern roundabouts"—more on that phrase in a moment—most of which were built in the last decade. As engineer Ken Sides noted in the ITE Journal, however, in 2008 Australia built its 8,000th roundabout; by Sides' calculation, the United States would need to build roughly 148,519 more roundabouts to match the Australian rate per capita. Interestingly, Australia—a country whose traffic landscape is rather similar to ours—has, since 1980, cut its traffic-fatality rate to nearly half the U.S. figure. The rise of roundabouts has no doubt played some part.

Why are Americans so suspicious of roundabouts? The simplest answer is that we have grown used to (and feel comfortable with) binary, on-off traffic control. We suspect such signals are more efficient than the "fuzzy logic" that seems to govern roundabouts. Roundabouts require drivers to make their own decisions and assess others' actions, rather than relying on third-party signals.

And here is the link..

[IronTiger]

New Jersey (particularly Cherry Hill) had a ton, but sometime later they were "redone". Like this one: http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Cherry+Hill,+NJ&sll=37.0625,-95.677068&sspn=40.460237,76.640625&ie=UTF8&ll=39.893501,-74.927621&spn=0.0024,0.004678&t=h&z=18

I believe this was one too: http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Ponzio's+New+jErsey&sll=39.902428,-74.972591&sspn=0.019194,0.037422&ie=UTF8&ll=39.9136,-75.01026&spn=0.002399,0.004678&t=h&z=18

Look at the empty space around the intersection, the bizarre entrance to Kings Hwy. S and the "stub road".

Something is weird with this one: Street View shows roads that weren't there before.

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Ponzio's+New+jErsey&sll=39.902428,-74.972591&sspn=0.019194,0.037422&ie=UTF8&ll=39.919183,-75.088581&spn=0.002399,0.004678&t=h&z=18

[ihop]

I was in Sedona, AZ recently, where they replaced a few intersections along hwys 179 & 89 with roundabouts just under a year ago. They're at intersections where the major thoroughfare through the town is a state hwy, with small cross streets. Apparently they've been pretty effective at reducing congestion.

[jamesf]

The city of Meadows Place, a small city bordering Houston, Stafford, and Sugar Land, is planning on installing a series of four roundabouts on S. Kirkwood between W. Bellfort and W. Airport. They will replace the four stop signs within 300 yards of each other within the neighborhood. They are being billed as a traffic calming measure as S. Kirkwood runs through a residential neighborhood. The traffic along S. Kirkwood in that area is static and not expected to grow any. They will be reducing the road from four lanes to two lanes in the area so they are able to fit within the right-of-way. You can see more about it here.

[samagon]

I think a lot of people imagine intersections like westheimer and hwy 6 as being a roundabout, that just doesn't make sense, but for intersections that don't have a lot of flow, but do have streetlights (that you sit at for a minute with no one but you) it would be a good thing. It slows down the traffic, because you have to turn, but it doesn't waste fuel.

I also think that some signals are needed, but not all the time, better automation of the signals is key, between certain hours it could be a blinking signal, this would take a lot of research and observation though to determine when the lights should be timed.

[LTAWACS]

Montrose & Main, and there is one under the Gulf Freeway at Park Place & Broadway.

The latter has semaphores at all points. So it might as well just not count because one still have to stop no matter from which street one approaches.

[Subdude]

Americans whine about roundabouts!

Traffic is going in circles. Armed with mounting data showing that roundabouts are safer, cheaper to maintain and friendlier to the environment, transportation experts around the country are persuading communities to replace traditional intersections with them.

There’s just one problem: Americans don’t know how to navigate them.

“There’s a lot of what I call irrational opposition,” said Eugene R. Russell Sr., a civil engineering professor at Kansas State University and chairman of a national task force on roundabouts, sounding mildly exasperated in a telephone interview. “People don’t understand. They just don’t understand roundabouts.”

But many are being forced to learn, 25 years after Clark Griswold captured the public’s unease with roundabouts in “European Vacation,” spending a full day circumnavigating London’s famous Lambeth Bridge roundabout — “There’s Big Ben, kids! Parliament!” — unable to escape its inner lane.

The Department of Transportation does not keep statistics on roundabouts, but experts agree that they are proliferating rapidly. They point to Wisconsin, which has built about 100 roundabouts since 2004, and plans to build 52 more in the 2011 construction season alone. Maryland is closing in on 200. Kansas has nearly 100.

All told, there are about 2,000 roundabouts in this country, most built in the last decade, according to Edward Myers, a senior principal at Kittelson & Associates, a transportation engineering and planning firm.

That does not mean they are usually well received.

For instance, residents of Quentin, Pa., near Harrisburg, were distraught to learn last month that a stoplight intersection in town might be turned into a roundabout.

“I just foresee a lot of accidents,” said John Horstick, 61, who owns the Quentin Haus, a nearby restaurant. A petition circulated at the restaurant garnered hundreds of signatures in a matter of days.

Kitty Schaeffer, 81, said she was worried about large trucks navigating the circle. “Let’s just have a light there, and when the light changes, you just go,” she said.

NY Times article link

[barracuda]

I drove through a town in Indiana that had replaced intersections with roundabouts with one main inner-lane. The problem was that during rush hour, a steady stream of traffic going down one specific higher-speed road leading to the circle made it nearly impossible to get onto the roundabout from the other road. It helped keep the rush hour traffic flowing, but caused backlogs on the smaller streets. I think roundabouts are only effective when there are multiple lanes to allow more opportunities to enter, like the Main St./Montrose/Hermann Drive loop.

[sidegate]

I drove through a town in Indiana that had replaced intersections with roundabouts with one main inner-lane. The problem was that during rush hour, a steady stream of traffic going down one specific higher-speed road leading to the circle made it nearly impossible to get onto the roundabout from the other road. It helped keep the rush hour traffic flowing, but caused backlogs on the smaller streets. I think roundabouts are only effective when there are multiple lanes to allow more opportunities to enter, like the Main St./Montrose/Hermann Drive loop.

I'd like to see that one made into a true roundabout, such that traffic already circulating is not required to give way to oncoming traffic, which is currently the case with that one, and the reverse of the situation in a true roundabout.

[Witch King]

What about these 2 small roundabouts: Benignus @ Perthshire and Benignus @ Kingsride?

I have to manouvre around these when I mosquito fog this neighborhood at night!

Benignus @ Kingsride

http://maps.google.c...2,20.21,,0,8.04

[Subdude]

What about these 2 small roundabouts: Benignus @ Perthshire and Benignus @ Kingsride?

I have to manouvre around these when I mosquito fog this neighborhood at night!

Benignus @ Kingsride

http://maps.google.c...2,20.21,,0,8.04

Interesting. There is a stop sign in the background. What's that about? Isn't one of the points of roundabouts to eliminate stop signs? Also, it is odd to see such a small roundabout with landscaping. The smaller ones I've seen are usually sort of a round bump in the road. I think the idea is so large trucks or emergency vehicles can get through if necessary without destroying the decoration.

[samagon]

Interesting. There is a stop sign in the background. What's that about? Isn't one of the points of roundabouts to eliminate stop signs? Also, it is odd to see such a small roundabout with landscaping. The smaller ones I've seen are usually sort of a round bump in the road. I think the idea is so large trucks or emergency vehicles can get through if necessary without destroying the decoration.

I remember when they put in these 'roundabouts' I had an aunt living in the area, so I got to hear all about them going in.

Apparently, those were done because people were using those roads as through streets and driving exceedingly fast, there were some accidents caused, and possibly even a fatality, iirc (almost 20 year ago now).

I remember very clearly that after they initially put them in there was a big to do on the radio about it, cause there was apparently a fire in the neighborhood, and because they hadn't designed these 'roundabouts' with fire truck clearance in mind, it was difficult for the fire trucks to get where they needed to go. they had to go back and fix it by making those sidewalk ramps, previously it was all curb, so they made a ramp, giving enough room for fire engines to swing around.

Anyway, yeah, those aren't in place to help traffic move easier, they were put in place to slow people down (this was before road humps were invented). I haven't been down those streets in forever, but I wouldn't be surprised if they went back and added road humps as well.

Here's a proper roundabout in Houston...

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Meadowglen+Lane,+Houston,+TX&sll=29.729543,-95.327272&sspn=0.013546,0.01929&ie=UTF8&hq=&hnear=Meadowglen+Ln,+Houston,+Texas&ll=29.731477,-95.554764&spn=0.003387,0.004823&t=h&z=18

[20thStDad]

Most of the high traffic roundabouts I've seen in England have traffic lights, it's not a free-for-all. Those are usually just on smaller roads. A roundabout with lights is still useful, it allows for new traffic to start going well before the previous traffic exits the intersection.