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Journal fiannaFailMan's Journal: Why roundabouts are better intersections 28

Journal by fiannaFailMan
My last journal entry got a good response, so here's one in a similar vein.

Interesctions in the US, especially in California, are of the four-way type. You either have a four-way stop, or a four-way traffic-light junction. These are both inefficient and they are death-traps. Why?

Let's start with the inefficiency. At larger suburban intersections the cycles on the lights are very long. If you stop just as a light turns red and you're waiting for the left arrow, you can be sitting there for a good few minutes. Traffic is going to back up behind you. This can create problems further back at the previous junction, so to avoid it, what do we do? We build extra lanes, not to accomodate all that moving traffic, but to store stationery vehicles stuck at the lights. This contributes to the horrors of sprawl as well as being a monumental waste of resources.

From the motorist's point of view, it turns his journey into one big stop-and-go session. No wonder automatic gearboxes are so popular in America, the amount of stop-n-go driving is unreal! And regardless of whether your transmission is automatic or manual, stop-n-go driving is not good for your engine, fuel consumption, or the environment.

Now let's take the safety issue. How does a 4-way stop-light encourage you to drive? That's right, it gives you an incentive to speed through it at the most dangerous time, i.e. when the light has just turned amber. I read that a third of all crashes happen at intersections. This is not one bit surprising.

Then you have the four-way-stop. These are fine, but what happens when you come to a stop sign where the cross-traffic does not stop, but there's no sign saying so? Someone approaches the stop sign, stops, sees a car coming from the side, assumes that he has right of way, moves off, *BANG!*

So. What are the alternatives? One word. Roundabouts.

Anyone who has been to Europe will have seen them because they're everywhere. For the uninitiated, these are 'yield-at-entry' traffic circles. As you approach the roundabout, you slow down as it flairs off to the right (in a country where you drive on the right) and you approach a yield sign. If nothing is coming around the roundabout towards you, you drive on. If something is coming around the circle, you yield to him. In fact, you don't have to stop, it's better if you slow down and just fit yourself into any gap that comes around. Once on the circle, you drive anti-clockwise without stopping because everyone else approaching the roundabout now has to yield to you and you keep on going until you're off the roundabout and on your merry way.

It works on the principle that it's unlikely that a large number of vehicles are going to be going to be going in the same direction, so you never have to wait very long for a gap to open up. If a car is coming around but shoots off the roundabout into the exit before yours, that buys enough time for you to drive on.

Advantages? Well for one thing the traffic overall flows a lot better. You seldom have to stop, so there's no need for big wide roads to store stationery vehicles. They are also safer than 4-ways believe it or not. Studies show a reduction in the number of accidents where 4-ways are replaced by roundabouts. Reason? Well instead of giving the motorist an incentive to speed through to make the light, one is forced to slow down because of the curvature of the thing. Also, there are fewer points where a collision can occur. On a 4-way there are over 30 potential collision points, twice as many as on a roundabout.

Disadvantages? Bigger roundabouts can be difficult for cyclists to navigate. Also, because traffic flows more or less continuously, they are not suitable for urban centres where large numbers of pedestrians need to be able to cross the street. Lack of familiarity when they are first introduced would be a problem, but one that is easily overcome with public education campaigns.

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Why roundabouts are better intersections More

Why roundabouts are better intersections

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  • Listen... (Score:1, Flamebait)

    by Tickenest ( 544722 )

    I'm sure you're right, but you can't expect me to read that whole thing, right? I mean, I'm an American, so, like all Americans, if given the choice of having something done right or done fast, I'll choose fast.

    Stupid Americans. We're so stupid.

  • New Jersey has circles (Score:2, Interesting)

    by RogL ( 608926 )
    Visit New Jersey. Fairly widespread use of roundabouts / circles.

    First rule of driving thru a circle: he who hesitates is lost. Look like you aren't going to stop, and merge in. While you're in the circle, look like you're going to cut off anyone entering your path. Note: it helps to have an older American 4-door; previous rust is a plus, dents are better.

    Roundabouts can be useful, but multi-lane roundabouts can border on the insane, especially when traffic *entering* the roundabout has the right of way.
    • It's all about driver familiarity. I learned to drive in the UK (roundabouts are _everywhere_) and once you get used to them they're fine. Multi-lane is also fine, provided you stick to the rules governing the lanes:

      1) Get in a lane and stay in it - don't drift around.
      2) Consider a 4-exit roundabout (they can be 3-6 or even more but 4 is most common). If you are getting off at the first exit stay in the outer lane. If you are going straight across pick the middle lane (if there are 3) or inner lane (if the
      • Indicate.

        A translation for the Ill-Briterate: "Use your turn-signals i.e.: 'indicators'".
        Yes, this means you Mr. Born-and-Bred-in-Los-Angeles.

        going to be going to be going

        This was wonderful! You stopped, just as I hoped it might go on aways.

  • No discussion of Roundabouts would be complete without mentioning The Magic Roundabout [swindonweb.com]
  • I would love for intersections in america to be converted to roundabouts. I spent a weekend in the UK driving a Mini Cooper from London to Manchester to Bath and back to London. It was one of the better driving experiences of my life. The first day back to work I was really freaking out. I couldn't deal with the intersections. I never realized how inefficient they were. On the approach to my office building the last mile has 6 intersections with traffic lights. It takes no less than 10 minutes every
    • If the circle is big enough then you'd have plenty of time to pull out. And as I say, with a bit of education people will get used to them. There was a time when they had to be introduced for the first time to the UK and Ireland too.
      • Maryland seems to be installing a good number of these. They seem to be the smaller roundabouts though. The single lane version would appear to be safer to me as the double lanes I drive through often get straightened out by drivers. Don't know how many times I've had to slam the brakes to avoid a right hand turn from the inside lane.

        Pennsylvania (at least an area to the North West of Pittsburgh) started installing smart traffic lights that changed based on vehicle detection. The lights didn't exactl
  • Consider the laws of physics. Simply put, no two cars can exist at the same point in space-time. A traffic intersection has a specific goal, allow cars who desire to contend with other cars for the same space-time position (ie cross paths) to behave in an orderly, lawful manner. This means that intersection efficiency can be gauged by how many cars/min are allowed to exist within it. Overall size and construction effort is also a factor but we will neglect that here. In the US, we are fond of making mu
  • Roundabouts have been showing up in Utah over the last decade. I personaly love them, but the drivers around here are idiotic and don't know how to use them. I've even seen idiot teenage drivers speeding around and around and around and around them thinking they were funny. So far they are a novelty that anmuses kids, scares the elderly (my parents), but somehow manage to smooth things out after awhile.
  • The architect who designed the stree layout in Brasilia agrees with you. His wife died in a left-turn accident, so when he got the chance to design the streets for an entire city he used roundabouts everywhere. It's not possible to turn across traffic anywhere in the city.
    • On the contrary, I think I'd positively hate it because it suffers from the 'garden city' fallacy that permeated new city planning in the sixties. That place is so sprawled out that it's gonna become another Los Angeles where you can only get around by car and street life is relatively non-existent. I feel another journal entry coming on.
      • Well, I don't know what your comfort level is regading sprawl, but I found it to be rather densely built, and foot traffic was facilitated by easy-to-use pedestrian tunnels under the streets. I could go anywhere I wanted in the city on foot provided enough time, with a wide choice of routes.

        The real problem is that the city was designed for about 2 or 3 million people, and there's somewhere between 0.5 and 1 million actually living there, so the population is rather spread out. There's just nothing to dr
  • 1) Gigantic intersections like the Place de L'Étoile at the Arc de Triomphe in Paris. 12 avenues meeting at a ~7 lane roundabout is a recipe for disaster.

    The picture at http://www.paris.org/Curiosites/Etoile/etoile.jpg [paris.org] should explain it all.

    2) Signal controlled roundabouts. The Mad^WRed Cow Roundabout[1] on the M50 in Dublin (the one in Ireland (for the non-Irish here)) and the M50 interchange at Blanchardstown (also Dublin) are prime examples of how signal controlled roundabouts can go horribly wron

    • Roundabouts are supposed to preserve the flow of traffic and avoid disturbing it at all costs. What's the point in putting traffic lights on the damn things?

      It's a good question. Sometimes it's necessary during high-volume commuting hours. As I said in the journal, the idea is that it's unlikely that a large number of consecutive vehicles are going to be going in the same direction. However there are cases when this does happen, like when a lesser-used road [1] feeds onto a roundabout that also gets

  • My apologies if someone else mentioned this but New Jersey has mostly roundabouts and very few areas where you can turn left (mainly only for small/unpopulated roads where it's not a problem). Even when there are no roundabouts you often can't turn left (you go off the road to the right and get spun around to be facing the dir you would've been had you turned right). While initially a royal PITA when I wanted to make a U-Turn and had to drive a long distance before there was a U-turn spot, I've come to ap
  • we would call it a rotary
  • Actually, I once went to a bicycle/pedestrian advisory committee meeting in Sunnyvale, CA, and the cyclists on the committee seemed pretty bullish on roundabouts.

    I don't know their exact rationale, but personally, I've found roundabouts pretty easy to negotiate. (Of course, I am accustomed to riding my bike in a vehicular manner [tomswenson.com], as though I were riding a small, slowish car.) Well, in my new incarnation as a New York City bikie, going around Grand Army Plaza in Brooklyn had me looking over my shoulder a bu
  • While you do have a good idea, there are places where roundabouts just don't work. The college that I used to go to replaced a traditional intersection with a roundabout. And I have to tell you, no one really liked it. It was more dangerous than the intersection that they had there originally.

    See, I know being on a college campus does not help given how stupid the drivers usually are, but anyway... the problem was that this roundabout was placed at a 4-way intersection, though the majority of the peo
    • Again it's an education issue. People need the correct operation of a roundabout exlained to them.

      In the example you have cited, that is one example where roundabouts are maybe inappropriate as I explained somewhere else. But I have my doubts that there would be an increase in accidents. There are studies [langford.bc.ca] that show that roundabouts actually reduce the number of accidents. Yes there may be a few prangs because of people being confused, but this is insignificant compared to the number of crashes ina fo

      • One thing I guess that I failed to mention before is that the intersection had no light, but was instead a 4-way stop. So everyone had to stop. A roundabout involves 4 yield signs instead of 4 stop signs so to a college student, yield = go. So everyone thinks that they can enter the roundabout the moment that they arrive at it. Since they weren't forced to stop with a yield sign instead of a stop sign, there was an *increase* in cars pulling out in front of other cars.

        Another problem that this partic

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