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Roundabout Revolution Sweeping US
chrb writes "BBC News reports that U.S. cities are installing more roundabouts than ever before. The first British-style roundabout appeared in the U.S. in 1990, and now some cities — such as Carmel in Indiana, are rapidly replacing intersections with roundabouts. Supporters claim that roundabouts result in increased traffic flow, reductions in both the severity and incidence of accidents, and fuel savings. Critics say that roundabouts are more difficult to navigate for unfamiliar American drivers, lead to higher taxes and accidents, and require everyday acts of spontaneous co-operation and yielding to others — acts that are 'un-American.'" As a driver who's hit all of the continental U.S. states except North Dakota, I dread roundabouts and rotaries for all the near accidents (and at least one actual accident) I've seen them inspire, and have been unhappy to see them spread. Spontaneous driver cooperation doesn't necessarily need the round shape, either.
Roundabouts (or rotaries, or traffic circles, as they're known in parts of the U.S.) induce confusion and fear in many drivers, although they can be useful at times. This article from an insurance periodical suggests that it's aggressive drivers who are making rotaries more dangerous.
:)
I like rotaries for two reasons: when there's no traffic, it's nicer than having to stop at an arbitrary red light and wait for a mandatory 2 minutes while the lights cycle. Secondly, if I am not sure whether to turn or not, I can just take another spin around the circle until I see the street sign I'm looking for (assuming there is one, not a given on some of the sign-challenged Northeast roads).
But I loathe rotaries when there's a lot of traffic. You can sit there for a lot longer than you would at a red light. Plus, some places make a rotary out of a 5-way intersection which can be incredibly confusing. It's a tradeoff, I guess, but overall I'd rather drive in a straight line
it's = "it is"; its = possessive. E.g., it's flapping its wings.
I hate to reply to myself, but I thought I should mention one the single best uses of a roundabout I've ever seen. If one travels from Highway 417 in Eastern Ontario and heads south on March Road (I say this so people can look at a map if they'd like), it's a blindingly boring stretch of road. Mostly straight, a bit hilly, and lends itself quite amiably to speeding like an idiot. I've accidentally gone as much as 40 km/h over the speed limit (or about 20 km/h more than I was aiming for). This is fine for the country road, but eventually you get to the small town of Almonte, where the traffic picks up considerably.
In the past, I suspect this resulted in maniacs speeding through town, on their way to the next destination. However, by use of a roundabout, they forcibly slow people on their way in, putting them in a much better frame of mind for the town, without bringing traffic to a complete halt, and likely resulting in collisions from people running the stop sign.
Not only that, but the idiots who are likely to try and speed through anyways get themselves into trouble before entering the town and endangering the residents. I though that this was a genius little piece of civil engineering, and if I ever meet the man who thought of it, I'd gladly buy him a round.
Cynical Idealist
The fact is, it's harder to get a driver's license in a lot of other countries. The standards and expectations are higher. In the U.S., I exaggerate only very slightly to suggest that a driver's license (and even automobile ownership) are seen as a fundamental human right, rather than a privilege. Most places, public transit is something that poor people use until they work hard enough to live the American dream (with accompanying house in the 'burbs and two-car garage).
Many other driving nations impose stricter conditions on new drivers, graduated licensing schemes (which require the passages of time and/or tests before new drivers are allowed greater driving privileges--the use of high-speed highways, driving late at night, driving without another experienced driver, etc. may all be prohibited to new drivers), older minimum driving ages, and more complex driving tests than the United States.
Despite its abundant roundabouts, the UK enjoys a non-motorway death rate about 15% below that of the U.S. (Their motorway death rate is more than 60% less, but that's pretty much irrelevant to the roundabout issue.) Better public transit also means that people who can't or shouldn't be driving are less tempted to do so.
~Idarubicin
My first experience with roundabouts was during a vacation to Australia (Brisbane). They are absolutely everywhere and once I'd gotten used to the etiquette in play, I fell in love with them. I drove from Brisbane all the way north to a little resort where we were catching a chart to snorkle the Reef. Traffic never really stops, folks on the roundabout have the right-of-way, but the pace is deliberately slow so that merges on and off and controlled and traffic continues to flow.
You *cannot* run a red light or miss a traffic signal as the intersection usually has a garden or statue *right in the middle of traffic*. If you are somehow so inattentive or drunk entering the intersection that you miss the big wall in front of you, folks on the roundabout have plenty of time to recognize that you aren't going to stop as you *are* in their field of vision as they travel on the circle. They can either stop or take evasive action as you smash into the concrete barricade. Drivers are empowered and required to remain attentive, even when they have the right-of-way. As you need to make a tight circle while on the traffic circle, you *must* drop speed or you'll never make the turn. Accidents on a traffic circle tend to be low-speed with minor or no injuries.
A standard traffic light abdicates all responsibility to a device. Vehicles traveling in a straight line through an intersection tend to do so at or above the speed limit - so pedestrian and driver error is frequently catastrophic or fatal. I don't know about others, but I'll take an increase in fender-benders to avoid head-on or t-bone accidents.
http://www.iihs.org/research/qanda/roundabouts.html has some excellent information about roundabouts. Note in point 5:
"5 What are the common types of crashes at roundabouts? What can be done to prevent them?
Despite the demonstrated safety benefits of roundabouts, some crashes still occur. Fewer crashes are typically seen at single-lane roundabouts compared with multilane roundabouts.5
An Institute study of crashes at 38 roundabouts in Maryland found that four crash types (run-off-road, rear-end, sideswipe, and entering-circulating) accounted for almost all crashes. A common crash type at both single-lane and double-lane roundabouts involved vehicles colliding with the central island. These crashes, which often involved unsafe speeds, accounted for almost half of all single-vehicle run-off-road crashes. Collisions occurred more frequently at entrances to roundabouts rather than within the circulatory roadway or at exits. About three-quarters of the crashes involved property damage. There were no right-angle or head-on collisions, potentially severe crash types that commonly occur at traditional intersections.6
In the Maryland study, Institute researchers concluded that unsafe speeds were an important crash factor. Some drivers may not have seen the roundabout in time. Measures to alert drivers of the need to reduce speeds (e.g., speed limit signs well in advance of roundabouts) and increase the conspicuity of roundabouts (e.g., larger roundabout ahead signs and YIELD signs, enhanced landscaping of center islands, pavement with reflector markings) may help to reduce crashes at roundabouts. Certain design features such as adequate curvature of approach roads also may aid in reducing speeds."
A few places in Montreal use round-abouts with zebra crossings for pedestrians, with a small sign that says "100$ fine if you do not give priority to pedestrians". While there are always exceptions, it works pretty well.
Cars drive a bit slower, but given that they don't have long lights to wait for, it is generally faster. Win-win.
(which is a bit surprising, since Montreal is probably one of the worst cities in North America with regards to respecting road signs, by either motorists, cyclists or pedestrians, but my impression is that when removing road clutter, people kind of start thinking again)
One of the big pitfalls for roundabouts that I saw in Montana when they tried to implement them was not taking into account snow removal (at big deal in Bozeman, MT) and emergency vehicles. They placed large concrete islands in the middle of the intersection, and there was not enough room for the larger vehicles to navigate around it. The snow plows couldn't even see the island after a big storm and would run right over it.
They are not the end-all solution, but in certain circumstances, I can see where they would be beneficial.
I believe in de-evolution. God made the world perfect, man fell, and its been going downhill ever since!
The thing I find puzzling about the American resistance to roundabouts is that they actually contain no new concepts at all, you don't have to 'learn' anything to use them. Topologically, they are just a one way street with T-junctions.
Ever pulled out of a side street into one-way traffic? That's exactly what you do when you join a roundabout. Even turned off a one way street into a side street? That's exactly what you do when you leave.
To answer your question, have you ever walked along a main street and crossed a side street that didn't have traffic lights? That's exactly what you do when you cross at a roundabout.
A pizza of radius z and thickness a has a volume of pi z z a
Usually, they just cross --- I live in Reading, UK, and it's full of roundabouts that work like this. There's usually an island between the two lanes just as the road enters the roundabout; partly this is acts as a spreader to split the lanes and make the junctions easier to manage for cars, but as a side effect it gives pedestrians somewhere to stop in the middle, so they only have to cross one lane at a time.
When I started to drive I hated roundabouts; there were too many places to look and I couldn't track all the inputs needed to negotiate them safely. Once I got used to them, I really like them. They scale beautifully to the level of traffic and varying number of exits and can keep the traffic moving smoothly up to quite heavy loads. On really heavy traffic there's various tricks you can do to keep them working well: one cunning one is the use of spiral lanes. In this variant, as you approach the roundabout you move into the correct lane for your destination, merge onto the roundabout and follow your lane straight into the appropriate exit.
They're particularly good on motorway exits; a common approach is to have an elevated roundabout above the motorway, with sliproads connecting roundabout exits to the motorway. You can leave the motorway, merge onto the roundabout, and then it becomes trivial to select your exit either to a minor road or back onto the motorway in either direction.
They don't work well when the traffic isn't evenly distributed; imagine a four-exit roundabout with heavy traffic moving east-west and you want to get on to the roundabout from the south. You'll end up spending quite some time waiting for a gap, because you have to give way to the traffic that's already on the roundabout. If there's traffic coming from the north, it all works properly; they enter the roundabout, force the east-west traffic to stop to give way to them, which creates a gap that you can move out into.
They completely fail when you put lights on them. Once that happens, all the elegant traffic management falls apart completely and you end up with complicated, frustrating multistage junctions. There's one terrible roundabout in Reading (at Winnersh Triangle; locals will know it) where not only have they put lights on it but in a desperate attempt to solve the traffic problems have actually put a road straight across the middle. Years of tuning have reduced the irritation level to merely annoying, but it's still a poor junction. But then, there isn't really such a thing as a good junction at that level of traffic.
Right now the Reading council has a thing about replacing small, effective roundabouts with lights. Everyone is screaming high heaven about it. One set of lights they just put in (Shinfield Road) has pretty much doubled my commute time, due to lousy design, failure to do the research, delays, and generally Not Being A Roundabout.
Washington DC has rotaries, not roundabouts.
How about reading your own link:
"Traffic circle" is a term mainly used in the United States to describe a junction which in other countries would be called a roundabout.
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