7 ms·

A new kind of interchange eliminates left turns.

59 points by brianmckenzie 15y ago

ColinWright 15y ago
"New" ?? This was discussed 410 days ago:: http://news.ycombinator.com/item?id=1437430 http://news.ycombinator.com/item?id=1437430 Also just recently re-submitted: http://news.ycombinator.com/item?id=2833446 http://news.ycombinator.com/item?id=2833446 In particular, here's the WikiPedia article about the design: http://en.wikipedia.org/wiki/Diverging_diamond_interchange http://en.wikipedia.org/wiki/Diverging_diamond_interchange
- gojomo 15y ago
  New to most people; I haven't driven through one yet. And on the timescales of road engineering, pretty much anything novel in the past 20 years that's not yet widespread is still 'new'.
  - Semiapies 15y ago
    Also, the "new" is in the headline.
- deleted 15y ago
  [deleted]
chadgeidel 15y ago
I live in a town of spectacularly bad drivers so I may be jaded, but I just can't believe folks will "figure this out". People where I live have a hard enough time figuring out what lane they should be in on a straight two lane road let alone merging, signalling, stopping at intersections, one-lane roundabouts, etc.
- treeface 15y ago
  You might think so, but everyone says this everywhere in the world. For example, this is the top argument that people use against the implementation of the generally-safer, higher-throughput modern roundabouts. Without fail, every time a modern roundabout is installed, the exact same thing happens: congestion is eased, the incidence of fatal accidents falls some 90%, and a multitude of people say things like "well, I just couldn't believe that these people where I live were smart enough to handle it, but it worked!" What people usually attribute to bad driving is usually the fault of poor traffic planning. Humans tend to be the same, circumstances change.
  - asmithmd1 15y ago
    Massachusetts has the worst drivers in the the country - that is a fact - MA has the highest accident rate in the US. I blame the roads. Every intersection in MA is unique - there are no idioms. Take a look at these two intersections with 4 lane roads that were recently "fixed" Just keep moving or you will be stuck for hours: http://maps.google.com/?ll=42.361501,-71.070455&spn=0.002426,0.004823&t=k&z=18 http://maps.google.com/?ll=42.361501,-71.070455&spn=0.00... Something for everyone: overpass, circle, and jug handles: http://maps.google.com/?ll=42.24915,-71.171166&spn=0.00243,0.004823&t=k&z=18 http://maps.google.com/?ll=42.24915,-71.171166&spn=0.002...
    - treeface 15y ago
      Massachusetts has the worst drivers in the the country - that is a fact - MA has the highest accident rate in the US. A high accident rate is not proof that Massachusetts "has the worst drivers in the country". I've lived in Massachusetts (and New Jersey, California, and a bunch of other places that like to call themselves the "worst drivers"), but everywhere I go, it seems apparent to me that road conditions and layout account for the huge majority of deviations from place to place. For example, in New Jersey there are a ton of highways that don't have onramps (or about 15 feet of it). Because of this, there are a lot more (I mean a LOT more) collisions on the "onramp" and people generally are used to swerving in front of 65-mph traffic from a complete stop. In California you have just as many people (or maybe more) who swerve in and out of lanes at unreasonable speeds, but since there are so many lanes and since they're all so fantastically wide, that sort of behavior doesn't get punished as it might, say, on the Mass Pike or the Garden State Parkway. At the same time, city roads in California (at least in OC) tend to have much higher speed limits. This causes a marked increase in fatal collisions at these types of intersections...not because the people are inherently more aggressive, but because the roads shape their behavior.
      - cafard 15y ago
        I have often thought that the state seal of Pennsylvania should include a stop sign at the end of an on-ramp. It also has a way letting bridge abutments jut about halfway out into a lane so that the merge and exit lanes are divided.
psadauskas 15y ago
They have something similar near the town I grew up: http://maps.google.com/maps?q=columbus,+in+&hl=en&ll=39.200267,-85.957611&spn=0.006876,0.011244&sll=37.0625,-95.677068&sspn=56.768363,92.109375&t=h&z=17 http://maps.google.com/maps?q=columbus,+in+&hl=en&ll... It was terrible the first few years. Nobody could ever figure out which lane they were supposed to be in, and ended up driving on the wrong side of the crossed-over section. Granted, the people here are still having trouble figuring out roundabouts, but I found this very confusing my first couple times through the intersection.
m0nastic 15y ago
I didn't get very much sleep last night, but it seems like a more complicated solution than just using "jug handles".
- matwood 15y ago
  I'm glad someone brought this up. I think it's NJ that has a lot of jug handles and they do a pretty good job at eliminating all left hand turns and once I understood the term they were easy to use. I also think they would be easier to implement on existing roads.
juiceandjuice 15y ago
They started putting in lots of continuous flow intersections in Utah: http://en.wikipedia.org/wiki/Continuous-flow_intersection http://en.wikipedia.org/wiki/Continuous-flow_intersection
- vyrotek 15y ago
  The new Pioneer Crossing intersection is great. I drive through it every day. Here's a video describing the flow: http://www.youtube.com/watch?v=xWHEi8baCPE http://www.youtube.com/watch?v=xWHEi8baCPE
oflannabhra 15y ago
They're in the process of building one of these here in Lexington, KY. The link the the video simulation was definitely enlightening. We'll see whether drivers will actually be able to pick up how to navigate it.
pedalpete 15y ago
isn't each point of cross-over/merging a more likely point of failure? I could see there being less accidents of the left-turn variety being exchanged for more less-dramatic accidents. Aren't we better of just using roundabouts? or http://en.wikipedia.org/wiki/Roundabout#Turbo_roundabouts? http://en.wikipedia.org/wiki/Roundabout#Turbo_roundabouts??
digitalstax 15y ago
I lived a few blocks from the one in Springfield, MO when it was built. It just doesn't feel right at first. But I haven't heard of any problems and it seems to serve its purpose.
protomyth 15y ago
I cannot help but think this thing will be a nightmare in the snow. It just has a slide into the wrong place vibe.
savrajsingh 15y ago
You mean a roundabout?
murz 15y ago
Reminds me of Michigan left. http://en.wikipedia.org/wiki/Michigan_left http://en.wikipedia.org/wiki/Michigan_left
Bo102010 15y ago
There is one of these 300 meters from my apartment. It's not very confusing exiting the highway and turning left - just follow the lights. It is kind of confusing exiting the highway and turning right. Right-on-red is allowed, and to make such a maneuver you have to look in strange places for traffic that might hit you. I've almost messed it up a few times. The other option is to let people honk at you while you wait for a green. I'm curious as to what will happen when the power to the lights fails.

59 points by brianmckenzie 15y ago

"New" ?? This was discussed 410 days ago:: http://news.ycombinator.com/item?id=1437430 http://news.ycombinator.com/item?id=1437430 Also just recently re-submitted: http://news.ycombinator.com/item?id=2833446 http://news.ycombinator.com/item?id=2833446 In particular, here's the WikiPedia article about the design: http://en.wikipedia.org/wiki/Diverging_diamond_interchange http://en.wikipedia.org/wiki/Diverging_diamond_interchange

gojomo 15y ago
New to most people; I haven't driven through one yet. And on the timescales of road engineering, pretty much anything novel in the past 20 years that's not yet widespread is still 'new'.
- Semiapies 15y ago
  Also, the "new" is in the headline.
deleted 15y ago
[deleted]

chadgeidel 15y ago

I live in a town of spectacularly bad drivers so I may be jaded, but I just can't believe folks will "figure this out". People where I live have a hard enough time figuring out what lane they should be in on a straight two lane road let alone merging, signalling, stopping at intersections, one-lane roundabouts, etc.

treeface 15y ago
You might think so, but everyone says this everywhere in the world. For example, this is the top argument that people use against the implementation of the generally-safer, higher-throughput modern roundabouts. Without fail, every time a modern roundabout is installed, the exact same thing happens: congestion is eased, the incidence of fatal accidents falls some 90%, and a multitude of people say things like "well, I just couldn't believe that these people where I live were smart enough to handle it, but it worked!" What people usually attribute to bad driving is usually the fault of poor traffic planning. Humans tend to be the same, circumstances change.
- asmithmd1 15y ago
  Massachusetts has the worst drivers in the the country - that is a fact - MA has the highest accident rate in the US. I blame the roads. Every intersection in MA is unique - there are no idioms. Take a look at these two intersections with 4 lane roads that were recently "fixed" Just keep moving or you will be stuck for hours: http://maps.google.com/?ll=42.361501,-71.070455&spn=0.002426,0.004823&t=k&z=18 http://maps.google.com/?ll=42.361501,-71.070455&spn=0.00... Something for everyone: overpass, circle, and jug handles: http://maps.google.com/?ll=42.24915,-71.171166&spn=0.00243,0.004823&t=k&z=18 http://maps.google.com/?ll=42.24915,-71.171166&spn=0.002...
  - treeface 15y ago
    Massachusetts has the worst drivers in the the country - that is a fact - MA has the highest accident rate in the US. A high accident rate is not proof that Massachusetts "has the worst drivers in the country". I've lived in Massachusetts (and New Jersey, California, and a bunch of other places that like to call themselves the "worst drivers"), but everywhere I go, it seems apparent to me that road conditions and layout account for the huge majority of deviations from place to place. For example, in New Jersey there are a ton of highways that don't have onramps (or about 15 feet of it). Because of this, there are a lot more (I mean a LOT more) collisions on the "onramp" and people generally are used to swerving in front of 65-mph traffic from a complete stop. In California you have just as many people (or maybe more) who swerve in and out of lanes at unreasonable speeds, but since there are so many lanes and since they're all so fantastically wide, that sort of behavior doesn't get punished as it might, say, on the Mass Pike or the Garden State Parkway. At the same time, city roads in California (at least in OC) tend to have much higher speed limits. This causes a marked increase in fatal collisions at these types of intersections...not because the people are inherently more aggressive, but because the roads shape their behavior.
    - cafard 15y ago
      I have often thought that the state seal of Pennsylvania should include a stop sign at the end of an on-ramp. It also has a way letting bridge abutments jut about halfway out into a lane so that the merge and exit lanes are divided.

psadauskas 15y ago

They have something similar near the town I grew up: http://maps.google.com/maps?q=columbus,+in+&hl=en&ll=39.200267,-85.957611&spn=0.006876,0.011244&sll=37.0625,-95.677068&sspn=56.768363,92.109375&t=h&z=17 http://maps.google.com/maps?q=columbus,+in+&hl=en&ll... It was terrible the first few years. Nobody could ever figure out which lane they were supposed to be in, and ended up driving on the wrong side of the crossed-over section. Granted, the people here are still having trouble figuring out roundabouts, but I found this very confusing my first couple times through the intersection.

m0nastic 15y ago

I didn't get very much sleep last night, but it seems like a more complicated solution than just using "jug handles".

matwood 15y ago
I'm glad someone brought this up. I think it's NJ that has a lot of jug handles and they do a pretty good job at eliminating all left hand turns and once I understood the term they were easy to use. I also think they would be easier to implement on existing roads.

juiceandjuice 15y ago

They started putting in lots of continuous flow intersections in Utah: http://en.wikipedia.org/wiki/Continuous-flow_intersection http://en.wikipedia.org/wiki/Continuous-flow_intersection

vyrotek 15y ago
The new Pioneer Crossing intersection is great. I drive through it every day. Here's a video describing the flow: http://www.youtube.com/watch?v=xWHEi8baCPE http://www.youtube.com/watch?v=xWHEi8baCPE

oflannabhra 15y ago

They're in the process of building one of these here in Lexington, KY. The link the the video simulation was definitely enlightening. We'll see whether drivers will actually be able to pick up how to navigate it.

pedalpete 15y ago

isn't each point of cross-over/merging a more likely point of failure? I could see there being less accidents of the left-turn variety being exchanged for more less-dramatic accidents. Aren't we better of just using roundabouts? or http://en.wikipedia.org/wiki/Roundabout#Turbo_roundabouts? http://en.wikipedia.org/wiki/Roundabout#Turbo_roundabouts??

digitalstax 15y ago

I lived a few blocks from the one in Springfield, MO when it was built. It just doesn't feel right at first. But I haven't heard of any problems and it seems to serve its purpose.

protomyth 15y ago

I cannot help but think this thing will be a nightmare in the snow. It just has a slide into the wrong place vibe.

savrajsingh 15y ago

You mean a roundabout?

murz 15y ago

Reminds me of Michigan left. http://en.wikipedia.org/wiki/Michigan_left http://en.wikipedia.org/wiki/Michigan_left

Bo102010 15y ago

There is one of these 300 meters from my apartment. It's not very confusing exiting the highway and turning left - just follow the lights. It is kind of confusing exiting the highway and turning right. Right-on-red is allowed, and to make such a maneuver you have to look in strange places for traffic that might hit you. I've almost messed it up a few times. The other option is to let people honk at you while you wait for a green. I'm curious as to what will happen when the power to the lights fails.