Roundabouts vs Traffic Circles
Washington, DC is afflicted with a plague of “traffic circles” at places like Dupont Circle. These are very annoying for pedestrians, and also put drivers in the position of constantly facing imminent death. And don’t get me started on biking through Thomas Circle. One additional cost of all this madness is that if you go around town telling people that the country should have more “roundabouts” people look at you like you’re insane. These traffic circles are horrible, they say! But as Brad Plumer points out, a roundabout is actually something different and “modern-day roundabouts, in which incoming traffic yields to cars already in the circle, work quite smoothly, which explains why they’re creeping back in fashion.”
What’s so good about roundabouts? Well, relative to traditional intersections they lead to far fewer crashes and thus somewhat less congestion. This isn’t well-suited to every location, but it is something we ought to have more of.
62 Responses to “Roundabouts vs Traffic Circles”
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July 9th, 2009 at 4:08 pm
We hit a lot of roundabouts when driving around Scotland and Ireland. They took a little getting used to, but I could see the appeal in the long run. And fewer turns across traffic while we were getting used to driving on the wrong side of the road may well have saved our lives.
July 9th, 2009 at 4:08 pm
In Holland, biking around roundabouts is easy, as the bike paths usually form a square around the circle, if that makes any sense. I’d find a picture but I’m behind a work firewall that prevents image search!
July 9th, 2009 at 4:09 pm
In the more civilized regions of the country, they are called “rotaries”.
I think they’re great. Except when driving in England (which is full of them) if you’re not used to driving on the left side.
July 9th, 2009 at 4:10 pm
Roundabouts are safer for cars, but much more dangerous for bicycles unless you also build the bike lanes that alli talks about in Holland.
July 9th, 2009 at 4:11 pm
My county is finally relenting and putting in a roundabout at a problematic intersection. I was previously non-committal, until driving through a suburb of Sedona this last Christmas. It was a revelation, something even I, a rank novice and first time visitor, was able to grok on my first try in the middle of the night.
Looking at the on-line archive from their local rag, the usual selection of naysayers had fought it. I bet their grandfathers fought electrification.
July 9th, 2009 at 4:12 pm
My county installed a roundabout to replace a 4-way stop near my somewhat rural suburban neighborhood, and it has delivered on all fronts: far less congestion at both rush hours, fewer accidents, and greater overall convenience. Including the fact that they cost less to install, operate, and maintain than an improved intersection with traffic lights, it is a great solution that deserves widespread adoption.
July 9th, 2009 at 4:13 pm
The transition period, when a roundabout is first introduced to a community that has none, is truly beautiful. There was a donut shop on Lake Otis Parkway in Anchorage with a big sign saying “Stop the Circle of Death.”
The Anchorage rotary was actually a two circles in a row, in which the awesomeness is squared, not merely doubled.
July 9th, 2009 at 4:16 pm
There was a donut shop . . . .
Now that’s irony!
July 9th, 2009 at 4:19 pm
Meh, my experience traveling has led me to conclude that roundabouts are mostly used for putting up statues of dictators.
July 9th, 2009 at 4:23 pm
Brad’s definition of traffic circle is not universal. Traffic circles in many places, labeled as such, work exactly the same way as a roundabout.
July 9th, 2009 at 4:23 pm
I live and work in eastern suburbs of Cleveland, OH where I currently travel through one roundabout daily although I previously traveled through 3 daily. The city just a couple of years ago added a new one on the west side when they were doing some road configuration. It does make things move quicker, but you can instantly tell when someone in the circle has not encountered them often in the past because they appear totally scared s–tless or clueless on what to do.
July 9th, 2009 at 4:23 pm
But as Brad Plumer points out, a roundabout is actually something different and “modern-day roundabouts, in which incoming traffic yields to cars already in the circle, work quite smoothly, which explains why they’re creeping back in fashion.”
Sorry, but Brad Plumer is just plain wrong.
DC Code Title 18 Section 2208.7 very clearly states:
The driver of a vehicle approaching a traffic circle shall yield the right-of-way to traffic already within the circle unless official traffic control devices indicate
otherwise.
In other words, we already have roundabouts in DC. If you think our circles suck, then there’s no reason that changing their names to “roundabouts” (”Dupont Roundabout”?) is going to make them suck any less – either way, the entering driver is required by law to yield to those already in the circle.
C’mon – it’s even on the DC driver’s license exam.
July 9th, 2009 at 4:35 pm
Roundabouts suck for pedestrians. The lengthen the distance that needs to be walked, and there is no safe, traffic-free, place to cross a street.
Get rid of’em.
July 9th, 2009 at 4:36 pm
The ultimate roundabout is the Swindon Magic Roundabout in the UK.
July 9th, 2009 at 4:37 pm
Meh, my experience traveling has led me to conclude that roundabouts are mostly used for putting up statues of dictators.
Obama Circle, coming soon to NW Washington.
July 9th, 2009 at 4:38 pm
Here’s a photo and a video from a Dutch roundabout.
July 9th, 2009 at 4:38 pm
Dublin, Ohio (near Columbus) has built five modern roundabouts in the last four years and after my own initial skepticism, I must say that they work well to cut down congestion and accidents. But Dublin did not have bicyclists in mind when they built them and now is studying ways to make them more friendly. You can see a nice roundabout video here.
July 9th, 2009 at 4:40 pm
I’m not surprised Brad Plumer is wrong about this. It would be bizarre to require that people driving in the rotary have to give way to people entering it.
I do recall an extremely klutzy colleague who, several years ago, got “trapped” in the middle of one during heavy traffic and had to circle around many times before finally “escaping”.
July 9th, 2009 at 4:53 pm
I have a hard time seeing how a system that forces me to look away from the front of my vehicle and then accelerate swiftly is going to be better for pedestrians.
July 9th, 2009 at 4:54 pm
In the more civilized regions of the country, they are called “rotaries”.
A “rotary” is a “traffic circle” but a rotary is not the same thing as a “roundabout.”
Roundabouts have some key design differences that distinguish them from rotaries, with the primary difference being that roundabouts are designed primarily to reduce the speed of traffic going through the circle.
A well designed roundabout will allow most cars to enter the junction without stopping, while reducing their speed enough that any collisions that may occur won’t be severe. The traffic pattern reduces accidents because they eliminate the accidents caused by left-hand turns that would be made across traffic at a conventional intersection.
The old fashioned rotaries in New England are not roundabouts. Rotaries are actually hazardous because they usually aren’t designed to slow cars down, and would generally require extensive redesign in order to convert them into roundabouts.
It would be bizarre to require that people driving in the rotary have to give way to people entering it.
Until several years ago, the law in France was to give priority to the traffic entering the roundabout. Definitely not a good idea, which explains why they scrapped it.
July 9th, 2009 at 4:59 pm
Recalling my last visit to D.C., the problem with (what I recall to be) DuPont Circle was that it was broken up by a series of *!$#@ traffic lights. Whether on foot or behind the wheel, it was seriously messed up.
July 9th, 2009 at 5:00 pm
Re: The old fashioned rotaries in New England are not roundabouts. Rotaries are actually hazardous because they usually aren’t designed to slow cars down, and would generally require extensive redesign in order to convert them into roundabouts.
Frankly, I don’t care. We like our rotaries, and we aren’t giving them up. Massachusetts without rotaries might be hipper, more modern, and more rational, but it would not be Massachusetts. We have no desire to become a carbon clone of the rationally designed Portland Suburbs. No thank you.
July 9th, 2009 at 5:08 pm
The problem with DCs reoundabouts is that they have been converted to typical intersections that just happen to be in a circular pattern. Sometimes this is done for no good reason – traffic is limited and could handle the load. However, in most cases its because the traffic volume and number of streets converging overloads the roundabout i.e. Dupont Circle where Mass,Conn, 19th, and P meet.
July 9th, 2009 at 5:16 pm
No. Roundabouts are like the metric system: it’s some crazy European innovation that probably offers a marginal improvement but I will never, ever be comfortable with.
July 9th, 2009 at 5:19 pm
It’s the bootstrapping / learning curve that makes it tricky: you need people who know how to drive roundabouts when you build them, or you need to do decent education and signage on how to use them, otherwise people get into bad habits early on — mainly, stopping on the roundabout itself.
(The biggest efficiency comes when there are inner/outer lanes.)
Roundabouts suck for pedestrians. The lengthen the distance that needs to be walked, and there is no safe, traffic-free, place to cross a street.
Seen many six-lane drags outside big city downtown areas with pedestrian crossings at the crossroads? Didn’t think so.
July 9th, 2009 at 5:29 pm
I adore rotaries. And doing seventy on Storrow in the driving rain during rush hour.
Less idiosyncratically, rotaries seem most successful where 80% of the cars will want to take the same left out of the rotary. Otherwise, things start to get complicated with cars caught in the inside lanes (or piling onto the right lane leading up to the intersection). It doesn’t strike me as a cookie-cutter solution to intersections.
July 9th, 2009 at 5:33 pm
I’ve only lived in Maryland for 20 years, but I’m told that it used to be that the roundabout in College Park was the only one in the state. Now, Maryland seems to be roundabout crazy. Up in Howard County, they started using them over the last decade in a number of places.
I’m not so crazy about them, since they seem to create confusion, but this page has some arguments for them.
July 9th, 2009 at 5:37 pm
Also they save energy and cut down on carbon emissions.
July 9th, 2009 at 5:37 pm
My parents live in a town governed by a power-mad mayor with a fetish for roundabouts, who has built dozens of these things in recent years.
Currently, they are tearing out all the stoplights on a major 6-lane traffic artery and replacing them with on-ramps that are fed from traffic circles. The cross streets overpass the highway on bridges that have a pedestrian walkway, while the through traffic zips along unimpeded.
It’s an interesting model.
July 9th, 2009 at 5:37 pm
You can put crosswalks and pedestrian yields/signals on roundabouts where there is a need. And thanks to typical “splitter islands” you are usually only crossing one lane at a time on heavy traffic roads.
July 9th, 2009 at 5:44 pm
They lengthen the distance that needs to be walked, and there is no safe, traffic-free, place to cross a street.
A properly designed roundabout won’t have spoke roads with a lot of traffic lanes in the approach. They should generally be two- or four-lane roads at most.
The roundabout approach is supposed to be designed to get people to slow down to a speed that is low enough that they can stop if they have to, which makes them safer for cross traffic and for pedestrians. It does make for a longer walk, though.
Junctions of large, wide boulevards aren’t ideal places to install roundabouts, because there are too many lanes. You often need traffic lights for those, possibly with separate pedestrian crossings that go above or below the road.
July 9th, 2009 at 5:46 pm
I’ve lived in cities where they had them, and I’ll say while they do have their uses (and occasionally their charm), they’re absolutely awful at intersections that have a lot of traffic, and can cause traffic to backup for miles.
July 9th, 2009 at 6:07 pm
I love roundabouts, but can they please avoid multi-lane roundabouts? I live right near a two-laner that is fairly new and you’d be surprised (or not) at people’s inability to read the sign posted at entry telling how the lanes work (right lane going into the roundabout is for exits one and two, left lane for two and three). I nearly got wrecked by someone in the right lane trying to get to exit three while I was going into exit two from the left lane. This set up makes things tricker for biking too.
July 9th, 2009 at 6:14 pm
Roundabouts are indeed becoming much more popular in the Pacific NW. I am kind of a safety bug myself, so I approve. We have one on a VERY high traffic roadway near where I live, and while it does back up a but at peak traffic times, the waits are still not long as traffic flows through it quickly, and no one is getting killed or injured or having their automobiles block traffic for 30-60 minutes or more after an accident. I think the aggregate effect is smoother and faster traffic flow even without counting the beneficial social and economic effects of fewer injuries and fatalities.
July 9th, 2009 at 6:18 pm
I’m intrigued by this idea of a “modern” roundabout.
a) Living in England, I’ve never known a world without roundabouts. Except when I visit my family in the States
b) It’s just a round bit of grass with roads leading to it. How can it possibly be old or modern?
July 9th, 2009 at 6:22 pm
Speak for yourself. This Masshole hates those fucking things. Your comment, though is a good illustration of some of the reactionary sentiments than often run through this place. The provincial nature of New England can be really quite annoying.
July 9th, 2009 at 6:50 pm
Yes. All over Phoenix. And they’re starting to put in roudabouts and I’m the only one who likes them. Of course I’m from Boston so I would right?
There’s one in my hometown that has a stop sign facing the entering traffic. It was nescessary because the rotary was built so that only one of the incoming lanes is actually in the rotary and so the other two lanes almost never stopped. Plus that was the only place for pedestrian crossings. Cops made bank sitting at that intersection for the first few years after the stop sign went up. One cop, parks his bike next to the church and just stands on the sidewalk pointing to cars and telling them to pull over. It was hilarious, he had 6 cars lined up waiting for him to get done with the first guy. And he was still pulling over more.
July 9th, 2009 at 6:57 pm
They are popular with the Street Bots.
July 9th, 2009 at 7:22 pm
Yes. All over Phoenix.
That’s better than the strip-mall drag near me, which has plenty of crossroads, but no pedestrian crossings. The light sequence is designed entirely around traffic flow.
you’d be surprised (or not) at people’s inability to read the sign posted at entry telling how the lanes work
I wouldn’t be surprised, and that’s the bootstrapping problem I mentioned upthread — in places where multi-lane roundabouts are an established part of road design, it’s generally part of the driving test to negotiate them correctly.
Like DTM, I’ve seen Americans adapt quickly to two-lane roundabouts in the UK and Ireland. I drew a little sketch showing that it’s the outside lane for everything in the first 180 degrees, and the inside lane for the the next 180 degrees, and they got the hang of it after the first few attempts.
July 9th, 2009 at 7:37 pm
A “rotary” is a “traffic circle” but a rotary is not the same thing as a “roundabout.”
Roundabouts have some key design differences that distinguish them from rotaries, with the primary difference being that roundabouts are designed primarily to reduce the speed of traffic going through the circle.
The old fashioned rotaries in New England are not roundabouts. Rotaries are actually hazardous because they usually aren’t designed to slow cars down, and would generally require extensive redesign in order to convert them into roundabouts.
Well, most of the rotaries in Maine, definitely the ones in Augusta and the new one in Sanford, tend to slow cars down when they enter. You have to yield to traffic on the left, and that requires quite a bit of slowing down. Maybe its different in Southern NE.
July 9th, 2009 at 7:44 pm
When they suggested a set of roundabouts to replace some traffic lights in the Town of Poughkeepsie, I thought it was a bad idea.
But they work wonderfully well! I go through two of them twice a day. In the early morning when there’s light traffic, nobody’s stuck at a light in an otherwise empty intersection. In the afternoon’s rush hour, it feels like they work more smoothly than the lights did.
July 9th, 2009 at 8:06 pm
So I dug up this Federal Highway Administration document on roundabouts, and it includes a section distinguishing roundabouts from rotaries/traffic circles (Chapter 1, starting page 8):
FHA Roundabouts
Basically, they list a bunch of attributes a circular intersection must have in order to be a roundabout (the categories are traffic control, priority, pedestrian access, parking, and direction of circulation), with the remainder being traffic circles (aka rotaries).
Incidentally, that document also discusses a wide range of issues, including bicycles and pedestrians and so forth.
July 9th, 2009 at 8:09 pm
I once drove from central France to the outskirts of Paris on small country roads for about four hours and never had to stop once because of roundabouts. They are much better than stop signs in low travel areas and, I think, somewhat better even in higher traveled areas.
July 9th, 2009 at 8:11 pm
Wouldn’t it less confusing to argue that our traffic circles need certain attributes that many do not now possess rather than using two different terms to refer to traffic constructs that are, in structure, virtually identical?
July 9th, 2009 at 8:51 pm
Wouldn’t it less confusing to argue that our traffic circles need certain attributes that many do not now possess rather than using two different terms to refer to traffic constructs that are, in structure, virtually identical?
I don’t think your premise is correct: the defining characteristics of roundabouts (per the FHA) can get into structural issues, directly or implicitly. Practically speaking, that means you couldn’t just make a few tweaks and turn all existing rotaries/traffic circles into roundabouts.
So, it makes perfect sense to view the genus as “circular intersections”, and then view roundabouts as a species within this genus (the FHA actually identifies two contrasting species, rotaries and “neighborhood traffic circles”, but we don’t need to get into that).
July 9th, 2009 at 8:55 pm
Roundabouts are awful. They require pedestrians to walk farther and usually are an excuse to have more roads coming into the same point, which means more streets to cross.
And crosswalks? Pedestrian lights? If you live in an area where drivers pay attention to those, get down on your knees and thank your deity of choice.
What inevitably happens with roundabouts is traffic in the circle will drive around until they come to their exit, then will swerve onto that exit without signalling or looking for pedestrians or bicyclists. And rather than slowing down as most vehicle have to do when making a right-angled turn, they accelerate as they want to get out of the roundabout.
Crossing a spoke of a roundabout if there is _any_ traffic in the roundabout is taking your life into your own hands.
July 9th, 2009 at 9:26 pm
Scott de B.,
The FHA document I linked has some sections in Chapter 5 on pedestrian safety that cite British, Dutch, and Norwegian statistics suggesting roundabouts are in fact safer for pedestrians than signalled intersections. It seems the fewer conflict points (see the discussion), splitter islands, and generally slower speeds outweigh the considerations you mentioned.
July 9th, 2009 at 9:31 pm
I live in New Jersey where at one time we had over 100 circles. These were mostly on state roads where the speed limit is 45 or 50 mph. They were pretty dangerous, especially for people who aren’t familiar with the area. They were so bad, we had to phase them out. I think there are a few still left.
http://en.wikipedia.org/wiki/List_of_traffic_circles_in_New_Jersey
July 9th, 2009 at 11:16 pm
Yeah, this is confusing. Having grown up with roundabouts in Australia, I found it totally bizarre to discover that America suffers from a severe lack of roundabouts. Aren’t you guys meant to be practical?
Remember, just because it was invented by the French and gaily adopted by the British, doesn’t make it bad!
July 10th, 2009 at 12:23 am
just because it was invented by the French and gaily adopted by the British, doesn’t make it bad!
The roundabout was actually invented by the Brits during the 60’s. It was meant to improve upon the American-style rotaries of the day in Britain that were failing to keep up with increasing amounts of traffic.
The traffic circle predates the car, and was not designed to manage high speeds. (Look at the Arc de Triomphe if you want an example of a design that probably worked well enough with horses and wagons, but doesn’t cope at all with high speed traffic.)
The idea behind the American rotary was to speed traffic up, which seemed like a good idea at the time, before WWII. But that proved to be dangerous as more people began to drive.
The roundabout works because it slows traffic down. At the time that the Brits came up with this, this was out-of-the-box thinking; it was counterintuitive back in the day to believe that slowing down cars could actually increase their overall travel speeds. Now, it’s clear that roundabouts can move more traffic than regular intersections because a steady slow speed leads to an overall higher average rate of speed than does stop-and-go traffic, particularly when the roundabouts reduce accidents that contribute to congestion.
July 10th, 2009 at 1:26 am
Just watch the Tour de France every morning on VS. You’ll get the chance to watch the peloton flow through the roundabouts of France.
I don’t believe rural France has any traditional intersections anymore.
July 10th, 2009 at 1:54 am
The cursed French. World leader in roundabouts. Pumping out one thousand of these babies every year. And they are beautiful. I could look at French roundabouts all damn day.
http://www.sens-giratoire.com/textesrp/diaporama.php?i=1&
That is where the Frog’s 68 billion dollars worth of stimulus money is going! They are paying thousands of engineers, construction workers, and landscape artists to everywhere create art out of intersections.
Killing three birds with one stone -traffic control, unemployment and national beautification. Quelle idee magnifique!
July 10th, 2009 at 9:03 am
Oakland County has recently added three roundabouts not far from me, and they generally work pretty well, except a fair number of Michiganians really are unclear on the concept. They follow the Michigan rule of “when in doubt go to the left lane”, then come to a complete stop at the roundabout to wait until there’s absolutely no traffic anywhere on the roundabout. The ones who really want to be teases then start, stop when they see a car somewhere, and start again. It’s easy for these clowns to have a line of ten cars behind them in the left lane of the approach. It makes it easy, though, to jump the line by going to the (generally empty) middle lane, pause to check out the traffic, and go for it.
I grew up in New Jersey, which had loads of circles, as noted, and negotiating traffic circles was a skill handed down from parent to child. We never went through a circle in High School driver’s ed, and the DMV examiners didn’t ask one to go through a circle as part of the licensing test. I suppose the teachers and examiners valued their lives too much to want to experience a circle with a 17-year-old.
July 10th, 2009 at 10:21 am
I think as an introduction to roundabouts, Americans should get used to indicators on pavement: A solid line across the lane means stop, a dotted line means yield, and a zebra stripe means don’t run over a pedestrian. Then always yield to the left.
As for pedestrians, they need pedestrian sanctuaries (those little islands of curb and greenery with a level patch of sidewalk which are wedged between lanes.) Then all you have to do is look in one direction before crossing a very short distance. But while we were living in Germany, most of the big roundabouts didn’t have pedestrians or bikes at all. The planners rerouted them so as to give foot and two-wheel traffic a short cut. Although some bicyclists took the roundabouts. The cars went slow enough and the drivers were very good-natured. They don’t hate cyclists in Germany the way they do in America.
The European Union has been pushing roundabouts because their engineering analysis shows that they can save about a third of their transportation fuel costs.
My main gripe after living with roundabouts a few years is that when I drop something on the floor, it can be more than an hour before I can stop to pick it up. Outside of cities, there are almost no corners any more.
July 10th, 2009 at 10:32 am
The great thing about roundabouts is their effect on throughput. The stuttering effect of stopping for 30 seconds every 400 yards while dealing with poorly timed traffic lights is maddening. If you have roundabouts instead of an (apparently) infinite number of traffic lights, traffic finds its own pace according to traffic density.
July 10th, 2009 at 10:35 am
Roundabouts vs. rotaries:
Rotaries, old-fashioned traffic circles, were designed so that entering the circle was almost like taking an exit ramp off a highway. A smooth, gradual drift to the right that requires little reduction in speed. Their purpose was to allow traffic to pass with the least interference with the driver’s forward progress.
Modern roundabouts are different, in that the roads intersect with them as something like a T-intersection, as when on road ends at another road. For a driver to enter a roundabout, it’s necessary to make something like a 90 degree right turn. Obviously, this slows speeds and provides more decision time.
Rotaries are traffic-facilitation devices. Roundabouts are traffic calming devices.
July 10th, 2009 at 10:50 am
BTW, the technical name for what I just described is “deflection.”
July 10th, 2009 at 11:18 am
They built a roundabout in my town, but because they are so rare around here, everyone slams on their brakes as they approach because they don’t know what to do. It doesn’t help that the city filled the center with high bushes that obstruct the view of traffic in the circle.
So, for these to work
1) People need to be accustomed to them.
2) Execution matters
July 10th, 2009 at 11:21 am
For some inexplicable reason, DC decided that a circle is not a substitute for other traffic-contol devices (e.g., stoplights, stop signs) but a nice blingy addition to them. So we end up with the worst of all possbile worlds — circles combined with a plethora of traffic lights and lanes that only go out of the circle, etc. They are truly awful. The boondoggle “improvements” to Thomas Circle have made it especially deadly — and they cause long traffic jams at rush hour. I’m not sure true roundabouts would work in DC, as the aggressive and careless driving culture is set against the social contract necessary for them to function (i.e., yield to those inside the circle). And because DC’s circles — particularly Dupont and Thomas, but to some extent Logan as well — create such swriling, multi-lane streams of vehicular chaos and road rage, the public spaces in the middle are quite underutilized, as it’s difficult and unpleasant to access them on foot and who wants to spend a nice afternoon on a little green island amidst something out of Jean-Luc Godard’s Weekend?
July 10th, 2009 at 12:16 pm
Seen many six-lane drags outside big city downtown areas with pedestrian crossings at the crossroads? Didn’t think so.
??? Where do you live? In Southern California pedestrian crossings are standard, and not just in downtowns. Take a look at the satellite maps on Google for car-oriented suburbs like Valencia, Fontana, or Rancho Santa Margarita, and you’ll see marked crosswalks at nearly all the major intersections.
July 10th, 2009 at 1:53 pm
Since traffic only travels in one direction, there are half as many lanes. This makes it twice as easy to leap over the moving cars to the center of the roundabout.
July 10th, 2009 at 4:37 pm
There’s actually at least one roundabout that meets the correct definition in DC. It’s called Grant Circle, and it’s located on New Hampshire Avenue about 5 or 6 blocks east of where it crosses Georgia Avenue. The roads enter it at more or less “right” angles, there are no lights, and it’s “yield to traffic in the circle” all the way around. Based on a half-assed perusal of GoogleMaps, it looks like Sherman Circle somewhat to the north also meets the definition. Like the more annoying circles closer to downtown, each of these roundabouts represents an intersection of four streets rather than two due to the state-named diagonals