Traffic lights for getting on and off the roundabout, and traffic that enters the roundabout actually has precedence over traffic that's already on it, contrary to common roundabout rules. Lots of accidents happen because of it, and I have no idea what made people think this was a good idea.
A large number of larger roundabouts in the UK have traffic lights at the entrances and exits. What do you find idiotic about it? Works extremely well to keep traffic flowing.
Lights by their design will stop traffic and reduce road capacity (they are ostensibly for safety rather than road use).
The point about a roundabout was to keep traffic moving, not stop it. If there are lights, there is no difference between a roundabout and a circular intersection.
Not really, the lights on large roundabouts are pretty dynamic. You have lights to stop people going further round the roundabout, coupled with lights to stop people coming on to the roundabout. But traffic flow is pretty continuous.
When setup well, it couples the good points of a roundabout with the good points of a basic intersection.
They're usually seen though where you have maybe 7 or 8 roads coming together. If you didn't have stop lights, people from the smaller roads would never be able to enter the roundabout.
I grew up in a state that makes heavy use of roundabouts, but they call them rotaries. In general they worked wonderfully for traffic control although I did see the end results of a horrific accident when someone managed to go the wrong way on one causing a head-on collision. The ramps were highly angled in the "right" direction so they must have done it on purpose, although I can't imagine why.
Now I'm in another city where they are adding them all over the place including a street I commute to every day. The roundabouts here are significantly more dangerous than the ones we had where I grew up. Not only do people here not know how to use them (it's not like they are making people re-take their drivers license tests after installing these things), but they are not as well designed; most of the roundabouts here are being retrofitted into existing small intersections that used to be four-way stops. There's not enough room to curve everything the way so if someone goes when it's not their turn, it's going to be a right-angle collision.
I think roundabouts are great in theory, but they need to be done right and people need to be made to learn how to use them.
Also in Colchester - it's been there a few years now. It confused a lot of people when introduced IIRC.. Although when you get used to them, they can really speed up the traversal from one side to the other.
Roundabouts seem to be spreading internationally, too. That’s at least my experience. My small hometown in Germany (pop. 40,000) went from no roundabouts only ten years ago to at least four today. My even smaller university town (pop. 30,000) also has at least four brand new roundabouts. My own impression is that roundabouts were very uncommon in Germany only a few years ago but are no uncommon sight today.
I have never heard of any protest against them in Germany, only recently the exact opposite happened: the city wanted to put a traffic light at an intersection which lead many people to demand (unsuccessfully, in the end) a roundabout.
We called them traffic circles in Syracuse New York. I drove through plenty of them in Ireland too, clockwise, which is a trip until you adapt to it.
I dream about roundabouts every time I'm stuck at a light in Silicon Valley and absolutely nothing is crossing the intersection. During rush hour here, the light stays green in one direction for several minutes, so you wait around a lot before you can get on to te main thoroughfares.
I dream about roundabouts every time I'm stuck at a light in Silicon Valley and absolutely nothing is crossing the intersection.
Rather than redesign the road, this could be resolved with intelligent traffic lights that notice traffic flow (or lack of it). The lights in my town change to this mode after dark and often I'll see them turn to red but a few seconds later go back to green as I approach them.
yes, traffic lights could be a lot more intelligent. If Microsoft Kinect can reliably detect what people are doing, traffic systems should be able to figure out how many cars and people are approaching intersections.
Its unfortunate that the costs and benefits of traffic solutions are not connected like they are for most things. It would be a no-brainer to fix this if one balanced hundreds of dollars per day of lost time versus the cost of upgrading. But separating who pays costs and who gets benefits is what government seems to do best.
If Microsoft Kinect can reliably detect what people are doing, traffic systems should be able to figure out how many cars and people are approaching intersections.
The systems around here just seem to have infrared cameras on the top to notice the presence of a vehicle, nothing quite so fancy as Kinect! :-)
Intelligent lights still won't work as well in a lot of situations. Roundabouts are just more natural.
Think of a situation where four cars approach a roundabout at exactly the same time. With a roundabout (and I've driven this exact situation in Germany) everyone can smoothly enter at the same time and continue on. No technology needed.
The OP was referring to waiting at lights in Silicon Valley, an area where there are literally thousands of 4 way intersections (as in most US cities). It would be impossible to convert every intersection (or even 10% of them) to roundabouts effectively (within a reasonable budget and maintaining the number of lanes American drivers are used to).
It would be easier to maintain the road layout and use intelligent lights to make the junction, say, 50% more efficient, than spend large amounts of cash making the junction, say, 80% or even 90% more efficient with roundabouts.
Roundabouts are no panacea and are commonly used in situations where other solutions would make sense.
One example is when a minor road crosses a major one. At rush hour, the traffic going straight across can saturate the roundabout. You end up with congestion in all directions due to both faster traffic having to slow down for the roundabout on the major road and the traffic on the minor road being "stuck" waiting for a gap. A crossroads with lights would work better in this situation but these are less common in the UK for large intersections.
This study* found:
39% overall decrease in crashes and a 76% decrease in injury-producing crashes.
Collisions involving fatal or incapacitating injuries fell as much as 90%.
Roundabouts make a lot of sense when designed properly, and in the right place. I love them (they're just plain fun to drive through), but these are probably the top issues:
1. We mid-westerners, by and large, have never seen a roundabout before, let alone know how to properly drive through them. They weren't even so much as mentioned in driver's training classes around here until a few years ago. Whenever a new one goes up, there's a lot of confusion. The most common problem is misunderstanding or ignoring the yield sign: Some people treat the roundabout like a circular four-way stop and others just zoom in without yielding and cut off the traffic already in the circle.
2. Inconsistent entrance and lane rules. We have two major roundabouts in this town, both installed within the last five years. One of them prohibits lane changes inside the circle, one doesn't. At one of them, traffic entering the roundabout yields to traffic in the roundabout. In the other, vice versa.
3. Building roundabouts in an area for no good reason. On I-75 outside of Saginaw, there's an overpass with on and off ramps. A few years ago, they tore out the traditional traffic signal used on every single other on/off ramp in the state and instead put a roundabout on each end of the bridge. This was a very silly thing to do because the traffic volume was not that high in the first place. Moreover, it's a very industrial area with lots of big trucks and oversize loads that now have to navigate the roundabout very slowly and very carefully just to stay in the lane and not run into passenger vehicles whose drivers aren't paying attention.
While living in France, I read a piece which claimed that roundabouts were safer in part because individuals perceive them as more dangerous (than lights, etc.). This leads people to pay more attention and be more careful when faced with a roundabout, which in turn leads to safer driving generally. If this psychological observation is correct, then what scares us about switching to roundabouts in the U.S. might be exactly what will make it safer to adopt them.
Also, Slate had a piece on roundabouts and safety with the following quote:
"Mentioning roundabouts seems to invoke some form of the famous "availability bias," which leads people make judgments based on the memories that can be brought most easily to mind. And so, the American who may have driven as a tourist in France or Greece a number of years back will shudder with recognition, associating the roundabout with terror and near misses. But motorists with such memories often fail to consider that they were driving as tourists in unfamiliar climes, perhaps only for a few days."
As a side note, there is something ironic about the pro-American / anti-Europe arguments that inevitably surrounds the roundabout discussion. It feels to me like roundabouts are much more American, following the libertarian strand running deep in this country. Round-about = gov't no longer tell you when you may (green) or may not go (red). Instead, it forces you to trust in yourself and your fellow citizens.
A lot of intersections in residential neighborhoods in Berkeley are very small roundabouts, about twenty feet across. This is part of the city's traffic calming policy (http://www.ci.berkeley.ca.us/contentdisplay.aspx?id=8238) , which also includes such things as random intersections that you just can't go through if you're in a car. As someone who doesn't have a car, I appreciate this, but I imagine that if I drove in town I'd be quite frustrated by the inability to use side streets. (Indeed, the main roads seem to be quite crowded.)
I know of four roundabouts in my area (Minnesota.) Two work just fine and are properly marked.
One is completely useless, it's actually a series of 6 roundabouts attempting to control traffic in a shopping complex. The traffic level is so low that it might as well be normal, uncontrolled intersections.
One is used instead of a cloverleaf or stoplights to control the on/off ramps to a freeway. It's terribly marked and there is no way to know what lane you need to be in or where you ultimately need to go unless you've used it before. I have actually seen people get so confused that they just slam on their brakes and stop in the middle of the thing.
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[ 2.9 ms ] story [ 70.8 ms ] threadhttp://upload.wikimedia.org/wikipedia/commons/8/85/KeizerKar...
Traffic lights for getting on and off the roundabout, and traffic that enters the roundabout actually has precedence over traffic that's already on it, contrary to common roundabout rules. Lots of accidents happen because of it, and I have no idea what made people think this was a good idea.
The point about a roundabout was to keep traffic moving, not stop it. If there are lights, there is no difference between a roundabout and a circular intersection.
When setup well, it couples the good points of a roundabout with the good points of a basic intersection.
They're usually seen though where you have maybe 7 or 8 roads coming together. If you didn't have stop lights, people from the smaller roads would never be able to enter the roundabout.
Now I'm in another city where they are adding them all over the place including a street I commute to every day. The roundabouts here are significantly more dangerous than the ones we had where I grew up. Not only do people here not know how to use them (it's not like they are making people re-take their drivers license tests after installing these things), but they are not as well designed; most of the roundabouts here are being retrofitted into existing small intersections that used to be four-way stops. There's not enough room to curve everything the way so if someone goes when it's not their turn, it's going to be a right-angle collision.
I think roundabouts are great in theory, but they need to be done right and people need to be made to learn how to use them.
http://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempste...
(I survived, but it was a close-run thing!)
http://en.wikipedia.org/wiki/Magic_Roundabout_(Swindon)
http://maps.google.co.uk/maps?f=q&source=s_q&hl=en&#...
(It's a large roundabout with 5 small roundabouts around it. Such that you can go round the large roundabout in either direction).
Great news the US is moving toward sanity.
Aced it mind.
I have never heard of any protest against them in Germany, only recently the exact opposite happened: the city wanted to put a traffic light at an intersection which lead many people to demand (unsuccessfully, in the end) a roundabout.
I dream about roundabouts every time I'm stuck at a light in Silicon Valley and absolutely nothing is crossing the intersection. During rush hour here, the light stays green in one direction for several minutes, so you wait around a lot before you can get on to te main thoroughfares.
Rather than redesign the road, this could be resolved with intelligent traffic lights that notice traffic flow (or lack of it). The lights in my town change to this mode after dark and often I'll see them turn to red but a few seconds later go back to green as I approach them.
Its unfortunate that the costs and benefits of traffic solutions are not connected like they are for most things. It would be a no-brainer to fix this if one balanced hundreds of dollars per day of lost time versus the cost of upgrading. But separating who pays costs and who gets benefits is what government seems to do best.
The systems around here just seem to have infrared cameras on the top to notice the presence of a vehicle, nothing quite so fancy as Kinect! :-)
Think of a situation where four cars approach a roundabout at exactly the same time. With a roundabout (and I've driven this exact situation in Germany) everyone can smoothly enter at the same time and continue on. No technology needed.
What would the intelligent stoplight do?
The OP was referring to waiting at lights in Silicon Valley, an area where there are literally thousands of 4 way intersections (as in most US cities). It would be impossible to convert every intersection (or even 10% of them) to roundabouts effectively (within a reasonable budget and maintaining the number of lanes American drivers are used to).
It would be easier to maintain the road layout and use intelligent lights to make the junction, say, 50% more efficient, than spend large amounts of cash making the junction, say, 80% or even 90% more efficient with roundabouts.
One example is when a minor road crosses a major one. At rush hour, the traffic going straight across can saturate the roundabout. You end up with congestion in all directions due to both faster traffic having to slow down for the roundabout on the major road and the traffic on the minor road being "stuck" waiting for a gap. A crossroads with lights would work better in this situation but these are less common in the UK for large intersections.
This study* found: 39% overall decrease in crashes and a 76% decrease in injury-producing crashes. Collisions involving fatal or incapacitating injuries fell as much as 90%.
* http://www.iihs.org/sr/pdfs/sr3505.pdf
1. We mid-westerners, by and large, have never seen a roundabout before, let alone know how to properly drive through them. They weren't even so much as mentioned in driver's training classes around here until a few years ago. Whenever a new one goes up, there's a lot of confusion. The most common problem is misunderstanding or ignoring the yield sign: Some people treat the roundabout like a circular four-way stop and others just zoom in without yielding and cut off the traffic already in the circle.
2. Inconsistent entrance and lane rules. We have two major roundabouts in this town, both installed within the last five years. One of them prohibits lane changes inside the circle, one doesn't. At one of them, traffic entering the roundabout yields to traffic in the roundabout. In the other, vice versa.
3. Building roundabouts in an area for no good reason. On I-75 outside of Saginaw, there's an overpass with on and off ramps. A few years ago, they tore out the traditional traffic signal used on every single other on/off ramp in the state and instead put a roundabout on each end of the bridge. This was a very silly thing to do because the traffic volume was not that high in the first place. Moreover, it's a very industrial area with lots of big trucks and oversize loads that now have to navigate the roundabout very slowly and very carefully just to stay in the lane and not run into passenger vehicles whose drivers aren't paying attention.
Also, Slate had a piece on roundabouts and safety with the following quote:
"Mentioning roundabouts seems to invoke some form of the famous "availability bias," which leads people make judgments based on the memories that can be brought most easily to mind. And so, the American who may have driven as a tourist in France or Greece a number of years back will shudder with recognition, associating the roundabout with terror and near misses. But motorists with such memories often fail to consider that they were driving as tourists in unfamiliar climes, perhaps only for a few days."
http://www.slate.com/id/2223035/
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As a side note, there is something ironic about the pro-American / anti-Europe arguments that inevitably surrounds the roundabout discussion. It feels to me like roundabouts are much more American, following the libertarian strand running deep in this country. Round-about = gov't no longer tell you when you may (green) or may not go (red). Instead, it forces you to trust in yourself and your fellow citizens.
One is completely useless, it's actually a series of 6 roundabouts attempting to control traffic in a shopping complex. The traffic level is so low that it might as well be normal, uncontrolled intersections.
One is used instead of a cloverleaf or stoplights to control the on/off ramps to a freeway. It's terribly marked and there is no way to know what lane you need to be in or where you ultimately need to go unless you've used it before. I have actually seen people get so confused that they just slam on their brakes and stop in the middle of the thing.