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foxtrapper wrote:Yep. They are planning that for the main street of my town. Only thing saving us right now is the economy, it's put the plan on hold, but only temporarily. We've got parts of it already. Messy.
The multi lane crossover traffic circle creates spectacular car crashes. Medivac pilots's are quite experienced landing helicopters there now.
That intersection is bigger than my town
Oh dear god. They just put a simple circle (roundabout, whatever) in a small town north of Harrisburg, and the police chief for that town went on record saying even he didn't know the procedure for going through it (which is just a whole incredible facepalm in itself). I can't imagine what the ignoranti of this area would do with either of those...
This is in the construction phase now and when it's all done, I will be traveling north on Hwy 41 (4-lane hi-way on the right) and go through 7 round abouts to get to County J (small N-S road on the left) to get to work. Right now its just the two lights at the highway and one more down a mile.
SEVEN Roundabouts!!!
New York has a new fascination with roundabouts, they put FIVE of them in a row at Exit 12 on I-87. That's five in 1/4 mile or so.... I agree that accidents occur at a slower speed with less damage and fewer personal injuries, but you know there's always the pinhead that has the right of way and doesn't know, gets planked from behind or cuts off three lanes of traffic because they think mirrors are for grooming.
OK, rant off 
I recall one roundabout I had on the way to work years ago. Half the time the SUV'ers going East-West seemed like they would simply put the hammer down and plow straight through, without looking or yielding. You got to be very good at picking out which Soccer Mom was going to simply go for broke and zip on through regardless of traffic levels.
<a href="View Larger Map">Here's the Intersection.
This one is in Keene, NH.
I like driving up to it with another car on my left, and making them make the decision on when to pull into the rotary.
The original intersection was a basic 4-way with a timer system on the lights that was terrible. There was always traffic backed up atleast 20 cars in each direction. Now it flows a lot smoother. Plus it's a decent size rotary too, so you can carry some speed through it late at night when there's little traffic.
Endorsed by the local collision and body shops, no doubt.
I'm sure these people are smarter than me, but the town I've lived in for the past 23 years is built around a rather large roundabout. 6 roads come together, and it has the highest traffic flow of any roundabout in Ohio. We just took another 6 way intersection a little further out of town and converted it to a roundabout. I used to complain about the one in the center, and wasn't really a believer until the second one opened. It really, really improved traffic flow. If I have a point, it's that these things work, so why devise something so incredibly complicated? I agree with Prodarwin here, you do eliminate the left turns across lanes, but that used to involve only a portion of the vehicles. Now EVERYTHING has to cross. I don't see it, but like I said, they're probably smarter than me. Or they're following a computer model that they better hope is correct!
Roundabouts are great, I like 'em. There are a couple of intersections here in town that would work much better with them than the usual short traffic light snarl. People here complain every time a new one is added, but according to the local paper a change in the parking design for one block of 7th avenue is going to cause the destruction of civilization - so I don't listen to them. That said, I'm not sure I'm ready for Swindon.
Traffic does weird things. The best flow isn't always intuitive.
In reply to Keith:
And another other possibility regarding this plan and the one you posted is that they likely have much more sophisticated tools to predict these things than they did years ago, so something that looks totally outrageous to us might actually work in practice. Or....It might actually work in theory, but become a disaster in practice. I have no idea which, but I too would like to see a video of this stretch of road come Monday morning.
i think the way this would be useful is if the majority of traffic coming through on the road are going to be getting on the freeway. this way, nobody has to wait at a light to get onto the freeway, they just peel off at the appropriate spot. i doubt it will have a great effect on the traffic flow across the intersection because in a "normal" overpass/onramp setup there would be two traffic lights anyways. the only difference here is that they both can't be green at the same time, so if you don't catch the light you might be waiting longer than you would have at the light, but cars/time could theoretically be the same.
Near me they replaced 1 traffic light with 3 roundabouts and an access road. Sounds complex, but the light was a huge backup for traffic (what NoVA light isn't?). I've driven through there many times since, and flow is improved by an incredible amount. And no lights at all!
I'm not sold on them for incredibly high volume intersections - although the one in Keene, NH looks interesting. I could think of about 20 intersections near me that could use that.
I have a nearby intersection of two state highways. Both two lane roads. Traffic light. During the summer, esp. on weekends, traffic can back up for a mile or more. Some going north to the lakes, while others going east to the races. Lots of crashes. Anyway, NYS has decided to install a roundabout. It will be interesting to see how it works out. I have driven those 914 driver speaks of, they are not bad. Better than a bunch of stop sign or lights.
Pedant warning: people confuse modern roundabouts with old fashioned rotaries/traffic circles. A lot goes into the design of roundabouts. In moderately busy areas they work great if they're well implemented. The old rotaries on the east coast are fine, but not so systematically engineered.
http://en.wikipedia.org/wiki/Roundabout#Difference_from_traffic_circles
Nice thing about roundabouts is that they reduce accident severity and—once people figure them out—frequency. A roundabout has no place for a head-on or right-angle to happen, traffic all moves in one direction, pedestrians never have to cross two opposing lanes of traffic, you get rid of some costs associated with signals, they never completely gridlock, etc. Plus, they're cambered to limit speeds such that just a little bit of throttle on exit is exciting. :)
These diverging diamond interchanges are rad. Definitely the sort of thing that would be a hard multi-million dollar sell to a planning commission back before they could be modeled in computers.
hotrodlarry wrote:This one is in Keene, NH.
I like driving up to it with another car on my left, and making them make the decision on when to pull into the rotary.
The original intersection was a basic 4-way with a timer system on the lights that was terrible. There was always traffic backed up atleast 20 cars in each direction. Now it flows a lot smoother. Plus it's a decent size rotary too, so you can carry some speed through it late at night when there's little traffic.
I just drove thru there last weekend. Thought it odd to have a separate lane for going left but it worked rather well.
and here in NJ they are ripping the traffic circles/roundabouts out as fast as they can.
I think a lot of it has to due with confusion. In the driver's handbook, you have to give way to traffic on your right.. but in a circle, traffic in it has right of way.. people get confused and just go.
They are ripping the one near me out right now, it's a nightmare that is destroying my car, so I go 5 miles out of my way to avoid it
even worse, i've had several people stop in the roundabout to let me enter the roundabout near my office. luckily its not a very busy intersection and i haven't seen anyone get plugged there, but i'm sure its bound to happen some time.. then there are other people that treat the yield sign like a stop sign and stop even when nobody is coming
