Road Planners Embrace the Diverging Diamond Interchange To Speed Up Traffic (npr.org) 200
schwit1 shares a report from NPR: When you first approach this bridge over Interstate 66 in northern Virginia, it may feel like you're driving on the wrong side of the road. Because, in a way, you are. "There were a lot of people who looked at me like I was a little nuts," says traffic engineer Gilbert Chlewicki, the inventor of this unconventional interchange. "Like, why are you putting me on the other side of the road?" Chlewicki agreed to meet at this intersection 35 miles west of Washington, D.C. to explain the workings of the diverging diamond interchange, as it's known. He was easy to spot, wearing a neon yellow vest for safety.
As you enter the interchange, the right and left sides of the road cross over each other at a stop light. You are, in fact, driving on the left side of the road at this point. From there, left turns become a lot easier, because there's no oncoming traffic in the way. Instead of waiting for a signal, you get a free left turn. "When we do the cross-over to the left side of the road, that's when the left turns happen, so the left is very easy," says Chlewicki. That means diverging diamond interchanges can be both more efficient and safer than conventional intersections with left turn lanes. There are now more than 200 of them across the U.S., in more than 30 states. But at first, it wasn't easy to convince other traffic engineers. "Anything different is a hard sell," Chlewicki said. "Safety was the big question." In 2009, Missouri became the first state to install a diverging diamond interchange (DDI) at a congested intersection in Springfield. This new design quickly reduced traffic congestion and significantly improved safety, with crashes decreasing by 40-50%.
However, drivers have mixed feelings about the design. Some, like school bus driver Logan Wilcox, feel it can be confusing and potentially dangerous for unfamiliar drivers. Others, like local driver Greg Peterson, praise it for improving traffic flow and reducing accidents.
As you enter the interchange, the right and left sides of the road cross over each other at a stop light. You are, in fact, driving on the left side of the road at this point. From there, left turns become a lot easier, because there's no oncoming traffic in the way. Instead of waiting for a signal, you get a free left turn. "When we do the cross-over to the left side of the road, that's when the left turns happen, so the left is very easy," says Chlewicki. That means diverging diamond interchanges can be both more efficient and safer than conventional intersections with left turn lanes. There are now more than 200 of them across the U.S., in more than 30 states. But at first, it wasn't easy to convince other traffic engineers. "Anything different is a hard sell," Chlewicki said. "Safety was the big question." In 2009, Missouri became the first state to install a diverging diamond interchange (DDI) at a congested intersection in Springfield. This new design quickly reduced traffic congestion and significantly improved safety, with crashes decreasing by 40-50%.
However, drivers have mixed feelings about the design. Some, like school bus driver Logan Wilcox, feel it can be confusing and potentially dangerous for unfamiliar drivers. Others, like local driver Greg Peterson, praise it for improving traffic flow and reducing accidents.
I think people get used to it... (Score:5, Informative)
Re:I think people get used to it... (Score:5, Informative)
They built one of these near where I live. They converted it from a "normal bridge", and at first they didn't really mark the lines on the road well, and the signs seemed vague. The worn in tire tracks in the road seemed to go where you shouldn't go unless you wanted a head on.
Now things "well established", and traffic seems smooth. The signs and traffic lights are clear, the marking on the roads seem intuitive.
The only bad thing, however minor, is there are some routes that take about a half of a mile because you are forced to take a right, then a U-turn, where before it was a matter of going through a traffic light.
We have some in Georgia. It works for me.
What I wonder about is whether the highway department will make an effort to maintain signage and regularly repaint the lane markings so to direct first-timers, drunks, or the slow to learn. Lane marking don't seem to be a priority around here. That and the need for good lighting at night.
The ones I've been through could use better signage. For example, the go-that-way arrows could be set ahead of the crossover instead of where it's too late,
and above the road like Interstate signs so people in small cars might see them.
Here's one:
https://www.google.com/maps/@3... [google.com]
Obvious, huh?
When there is heavy traffic, you can see what all the other cars are are doing, but you won't see the arrows on the street due to the other cars being bunched up. So your heart skips a beat or two from the wtf.
In the AM, it's not at all obvious to a drunk first-timer.
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I've run into a few of these in Idaho driving through Boise and Pocatello. They make getting on and off the freeway easier as most left turns do not need to cross traffic. The lanes swap sides, traffic coming off or entering the freeway make left turns into traffic flowing similar directions, then the lanes swap back.
The first time you drive through one of these interchanges it seems odd, but after that the advantages are obvious.
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Accurate and clearly written signage along with constantly maintained lines painted on the roads is CRITICAL for this to work.
Where I live it would soon become a fiasco & safety hazard since the State Road Department repaints the lines on the roads every decade or two. Thus, that paint fades away and road lines become impossible to see at night or in heavy rains.
The 'magic' roundabout (Score:5, Interesting)
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There are some roundabouts near where I live in the US. Even though they always go counter-clockwise they confuse people badly. I think having an inner and outer roundabout going in different directions would cause a lot of accidents in the US, a lot.
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That's where Turbo Roundabouts ( https://en.wikipedia.org/wiki/... [wikipedia.org] ) help. You don't do lane changes in the roundabout, you pick a lane before entering it and end up at the correct exit.
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That would require enough awareness to plan ahead.
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I don't know why Americans are so confused by normal roundabouts. I guess the yield rules, especially regarding the inner lanes, seem to run counter to some people's sense of right-of-way. An education problem perhaps.
Re:The 'magic' roundabout (Score:4, Interesting)
There's nothing American about the GP's comment. The inner ring / outer ring running in opposite directions is an insanely confusing design for people from any country, including in England. The Magic Roundabout has a significant higher accident rate than normal roundabouts in the UK. But the issue is simply the number of traffic junctions coming in made it the best design option.
But people in general are confused about things they don't commonly see. I hate UK roundabouts. None of the roundabouts in my country require a lane change mid roundabout to exit. Not as dumb as the All-way stop junctions from the US, but then where I live the existence of a stop sign is seen as a faulty intersection design, which is why the last stop sign from my city was removed in the late 00s, to say nothing of multiple stops. I recently got a speeding fine in Spain after exiting a roundabout because the design of the road made me think I was on a highway onramp so I was accelerating. Turns out it was a 50zone. The police officer didn't understand why I thought what I thought because he has normalised the traffic he drives in every day.
As does everyone. - Roundabouts aren't common in the USA so it stands to reason they will confuse more people. On the flip side roundabouts are frigging everywhere here.
Dougal's Sugar (Score:2)
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The magic roundabout is easy to understand if you think of it as 5 tiny roundabouts connected in a ring by 5 very short roads.
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Another interesting device is the nested roundabout [twistedsifter.com] in England. Cars go clockwise on the outer roundabout, as normal. A U-turn puts one on the inner roundabout going counter-clockwise.
They've been installing roundabouts here in South Dakota for a few years. However, our planners like to build up the center of the roundabout so you have no visibility around it. As a driver that's constantly scanning for the next vehicle or creature to enter my lane, it drives me batshit insane. And some of them have had some pretty massive pileups in their early days. I ended up liking the roundabout in places where I can see all the way around it. Once you get used to the flow, it's fast and easy.
Road Guy Rob on YouTube (Score:5, Informative)
If you find traffic engineering interesting, you probably already subscribe to Road Guy Rob on YouTube. In that case, you've known about diverging diamonds for several years now, so you're probably wondering like me why NPR finally noticed them.
https://www.youtube.com/watch?... [youtube.com]
Re: Road Guy Rob on YouTube (Score:2)
Roundabouts too (Score:4, Informative)
I first encountered roundabouts while driving around Bahrain during Desert Shield/Storm while I was in the Marine Corps and thought they were excellent. I wondered why we didn't have them in the US. Over the past 5 years roundabouts have been showing up in Northwest Ohio and many people hate them. I don't understand why. This diverging diamond seems like a great idea too. I can't wait to see them appear in my neck of the woods.
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I think some people just don't like change while others maybe just need some time to get used to it. A new roundabout went in near where I live on a route I very commonly drive on and early on I know I did find it a bit annoying as I wasn't used to them. Now I love the damn thing though, it is so much faster going through the intersection now. Most of the time I don't even have to stop.
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I don't understand why.
Confusion of something that isn't common. Simple really. I hate 4-way stop signs for the same reason. You should check out turbo-roundabouts in the Netherlands https://maps.app.goo.gl/G8xcr8... [app.goo.gl], can't change lanes within the roundabout. I hated them when I first saw them, the locals on the other hand love them and have issues with roundabouts in the UK where you *have to* change lanes mid roundabout in some cases.
Ultimately it's what you're used to.
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Example (Score:3)
Here is an example of one in Australia. It certainly does feel weird when you first use it but does increase traffic flow.
https://www.google.com/maps/@-... [google.com]
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Sounds about right.
In Australia you can't get on a ladder without a certificate. Makes everything expensive!
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It's just as expensive in the USA too.
Gilbert Chlewicki did not invent this interchange (Score:5, Informative)
As he freely admits, Gilbert Chlewicki did not invent this interchange. There have been French examples since the 1970s. As usual the wikipedia article on this subject is more informative than the TFA.
https://en.wikipedia.org/wiki/Diverging_diamond_interchange [wikipedia.org]
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As he freely admits, Gilbert Chlewicki did not invent this interchange. There have been French examples since the 1970s.
But those were outside of the anglophone world, so they don't count in a priority dispute. Or do we now measure energy in Mayers [wikipedia.org] instead of Joules [wikipedia.org]?
I live in Massachusetts, you insensitive clod! (Score:3)
Here, we relieve traffic congestion by making roads so shitty, people don't want to drive on them! And if that doesn't work, we take out traffic lanes, add arbitrary one-way restrictions, and jizz speed bumbs and bike sharrows all over the place like a teenage that's just discovered the internet.
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Here, we relieve traffic congestion by making roads so shitty, people don't want to drive on them! And if that doesn't work, we take out traffic lanes, add arbitrary one-way restrictions, and jizz speed bumbs and bike sharrows all over the place like a teenage that's just discovered the internet.
I didn't know anywhere in America had such forward thinking city planning. I thought everyone was too busy humping the tailpipe of their V8s to consider a world where anything other than MORE AUTOMOBILES is the answer to every problem.
They almost built one in Oakton, VA (Score:2)
They almost built one in Oakton, VA, but didn't for "reasons."
Southgate Drive at Virginia Tech has a half diverging diamond intersection that works quite well.
I don't know why the "I-66 Outside the Beltway" project in Northern VA didn't include diverging diamonds, though their original plans *DID* feature them. They, instead, built many roundabouts that many people are finding annoying and outright dangerous.
I have used this once (Score:2)
I have used this once (actually twice with the return trip), and it was confusing for basically everyone around me. Cars just moved through any empty lane that was available without regards to actual flow this was supposed to enforce.
Of course not having any prior exposure, nor seeing any proper road signs to direct traffic, this is expected.
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There is no flow to enforce. The whole point of this is that it doesn't matter what lane you're in, you don't need to turn across a road of two way traffic. The benefits of the DDI exist regardless of which lane you use to move forward.
Re: I have used this once (Score:2)
Just don't do traffic design like Texas (Score:2)
Multilevel? (Score:2)
IIUC this is a contra-rotating roundabout (Score:2)
As a one-time topologist, I see everything as doughnuts. In this case, the geometry is the same as a roundabout with lights at the entrance/exit junction, and rotating backwards. I'm not sure if that gains anything over rotating in the normal direction now there are lights as well. Of course, as a topologist, I'm not concerned with the amount of land required or costs...
Only when not full ... (Score:2)
If the traffic gets very heavy these fail badly
A multi-level one does not, and needs no lights either ..as do roundabouts - but the USA seems to want to have so many lanes these don't work
I have yet (Score:2)
good in rush hour, horrible at night (Score:2)
The hassle with those is they run on timers, not sensors. So at night when there's nobody around, you still end up getting stopped by 3 lights in a row if you're trying to turn 'left', and so it ceases to be faster but rather is a waste of 3 minutes of time sitting as the light in front of you turns red just as yours turns green (one of my biggest pet peeve of driving not involving 'people').
The real problem (Score:3)
Re:I can't figure it out! (Score:4, Informative)
There are some great videos on this by Road Guy Rob on YouTube.
https://www.youtube.com/watch?... [youtube.com]
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For whatever reason TFA's photos are only showing half of them, only showing one crossover. Every photo fails to show the "prior" crossover that already happened upstream on the other side of the major highway (for a forward-driving perspective).
Gives me the impression that this is good for traffic seeking the freeway but not to those simply going through. Former's probably the bulk of traffic.
Re: I can't figure it out! (Score:2)
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A cloverleaf is much more expensive and requires far more land.
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They also have the problem of the on-ramp coming before the off-ramp, leading to a lot more merging and weaving
Re: I can't figure it out! (Score:2)
To be fair, there isn't any reason both lights can't be green at the same time. I wouldn't recommend it, but there's nothing stopping it from happening.
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To be fair, there isn't any reason both lights can't be green at the same time. I wouldn't recommend it, but there's nothing stopping it from happening.
Of course, the next obvious improvement is to make it so that there are three levels instead of two, with one direction crossing above the highway and the other below the highway (or one above the other above the highway), and then remove the traffic lights entirely. There's no reason that both directions have to be at the same level.
Re: I can't figure it out! (Score:5, Interesting)
Of course, the next obvious improvement is to make it so that there are three levels instead of two, with one direction crossing above the highway and the other below the highway (or one above the other above the highway), and then remove the traffic lights entirely. There's no reason that both directions have to be at the same level.
No need to make it three levels. You can just put two roundabouts at the ends of the overpass (at interchange ramp terminals) - this is quite common in Finland.
In general, roundabouts replacing traffic lights is the standard approach now here in one-level interchanges, giving much, much better traffic flow than traffic lights.
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Of course, the next obvious improvement is to make it so that there are three levels instead of two, with one direction crossing above the highway and the other below the highway (or one above the other above the highway), and then remove the traffic lights entirely. There's no reason that both directions have to be at the same level.
No need to make it three levels. You can just put two roundabouts at the ends of the overpass (at interchange ramp terminals) - this is quite common in Finland.
In general, roundabouts replacing traffic lights is the standard approach now here in one-level interchanges, giving much, much better traffic flow than traffic lights.
You can do that, but it is likely to take up considerably more space than it would take to do a two-level bridge, which should take up less space than the one-level bridge.
Also, Americans tend to be even more scared of roundabouts than Tesla FSD is.
I mean yes, we should do more roundabouts, but unfortunately, I think that ship has mostly sailed.
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Roundabouts don't necessarily have to be huge. And also, Americans hate roundabouts, because the first time they tried them, they did it wrong.
It's all there: https://www.youtube.com/watch?v=atORPw-w83I [youtube.com]
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To be fair, there isn't any reason both lights can't be green at the same time. I wouldn't recommend it, but there's nothing stopping it from happening.
In heavy traffic (rush hours in large urban areas), there are going to be problems with cars not making it through the second set of lights and backing up enough to block opposing vehicles from going through the LR interchange.
Re:Deck chairs on the Titanic (Score:5, Insightful)
This isn't just about capacity. It's also about reducing the conflict points, so that accidents are drastically reduced.
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Re:Deck chairs on the Titanic (Score:4, Interesting)
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Were the States right to run the interstates right through cities? I think they were.
I've driven across a lot of this country, and I love that the interstates go right through major cities.
Here in Seattle, we've got an asston of public transit. I don't think they're mutually exclusive, particularly since the funding comes from different places.
The Interstates were largely paid for (90%) by the Federal Government,
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Oh look, there's the lie about EVs wearing out tires again, this time with the clever lung cancer angle.
"I can't be the only one for whom air quality is a concern"
No, but you're the only one shitting on EVs because of (poorly) alleged air quality concerns.
Re:Deck chairs on the Titanic (Score:4, Informative)
EVs are going to wear them slightly faster than a comparable ICE sedan would. But not really much faster than the far more common SUV.
as you note, the problem isn't EVs...it's tires and the multitude of wear particles we're putting into the environment - which all vehicles do a *lot* of.
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But not really much faster than the far more common SUV.
No, but *much* faster than the car it would naturally replace (20-30% is the figure I've seen).
Again, I don't see a problem with this.
We're worried about rubber particulates while the world is fucking burning? We need to start prioritizing these problems.
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We're worried about rubber particulates while the world is fucking burning? We need to start prioritizing these problems.
This. It's way easier to come up with a new design for rubber that doesn't shed as much than to come up with another viable alternative to fossil fuels.
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We need better numbers on that. When we switched to an EV we were able to get a much smaller car than the ICE that it replaced, because the interior layout gave us more usable space. Early EVs where the powertrain was changed but the chassis design didn't wasted a lot of space. A car designed from the ground up as an EV makes far better use of the space. So while the same sized EV car is likely more heavy than the comparable ICE, the car that people actually switch to may not be that much heavier.
And the ma
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We need better numbers on that. When we switched to an EV we were able to get a much smaller car than the ICE that it replaced, because the interior layout gave us more usable space.
What?
I've been in many electric cars. Their interiors are regular car interiors. And why would they be anything but?
Early EVs where the powertrain was changed but the chassis design didn't wasted a lot of space.
Early? I mean I've been in 2 coworkers Teslas about 100 times. One of them is less than a year old.
So while the same sized EV car is likely more heavy than the comparable ICE, the car that people actually switch to may not be that much heavier.
Ya, I sincerely doubt that.
And the majority of the increased tire wear is actually due to people being unprepared for just how much more torque they have from a standing start than the weight.
Nope.
Just simple kinetic friction.
Beyond that, the torque argument is silly anyway.
My car has a shit ton more torque than a model Y, and I'm not burning through tires anywhere near as fast.
I have a clutch. My car has as much torque as I want (up to its peak) availa
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I've been in many electric cars. Their interiors are regular car interiors. And why would they be anything but?
EVs can have a frunk! Worship the frunk! Bask in the life-changing convenience of the frunk!
At least, I think that's the theory. I didn't really get it, either.
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Do EVs really need to accelerate from 0 to 60 in 2 seconds? This whole race to have the best ludicrous mode is quite silly frankly. But I think the core issue is that if EVs didn't accelerate so quickly and wear out their tires, people would think they are slow and under-powered because of the lack of the "push me into the seat" force that they are used to feeling from traditional autos shifting. So manufacturers are cranking out ridiculous specs in torque and horsepower to accommodate people's stupidity
Re: Deck chairs on the Titanic (Score:2)
The world burning being existentially bad doesn't mean micro plastics aren't an equally bad problem.
Oceans are going to be literally dead in a few decades and your balls have plastic in them already. Lol
Both things are bad and both things have to be solved and aren't gonna be easy
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It's a simple fact, and an indisputable one.
A heavier vehicle *must* eat those tires quicker.
Is that a problem? Far fucking less than the current CO2 problem, so meh.
The only actual solution is to stop using cars, and I just don't see that happening for obvious reasons.
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Until you look at what kind of ICE vehicles Americans actually buy. Top 5 ICE vehicles by sales:
Ford F-series
Chevy Silverado
Dodge RAM/RAM pickup
Toyota RAV4
Honda CRV
Top 5 EVs by sales:
Tesla Model Y
Tesla Model 3
Chevy Bolt EV/EUV*
Rivian R1-series*
Ford Mustang Mach-E*
*sold less combined than the Model 3 or Model Y
As you can see, there are a lot of ICE trucks on the road that weigh as much as or more than the overwhelming majority of top-selling EVs in the US, namely the Model Y and Model 3. If you were to do
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Seriously?
You can't be that stupid.
People are not replacing their F150s with a Model Y.
You just presented two entirely unrelated data sets and claimed a relation to them that is beyond fucking absurd.
Re: Deck chairs on the Titanic (Score:2)
Uh, I've been driving ev for awhile. It's absolutely true you can chew a set of tires faster than any ice car I've ever had.
It's influenced by what model you're driving, how aggressive of a driver you are, and how regularly you stay on top of rotations and alignments.
While it's not a particularly good argument against evs, they definitely need to stay on top of tire care or you can absolutely chew tires up, and pretending otherwise is just incorrect.
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Induced demand means that putting individual people in their own personal boxes is never going to work.
And building new dense housing is never going to work either. No large city in Europe, USA, or Japan managed to even halt the housing price growth (never mind reversing it) by increasing density.
So here's the thing, the ONLY way to lower the housing price (outside of Detroiting your economy) is to build NEW low-density cities. There are literally no other ways. No amount of "streamlining regulation", "kicking NIMBYs", "raping cities with Salesforce-tower shaped sex toys" is going to work.
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The cost is human misery: increasing density forces people to cram into ever-smaller, and ever-more-expensive apartments.
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Study after study shows that people WANT to live in suburbia. There are brainwashed folx who are conditioned to say "suburbia bad", but they are a minority.
Re: Deck chairs on the Titanic (Score:2)
I donâ(TM)t want to live in suburbia. No thank you. If I have to own a car, Iâ(TM)ll go and live in the countryside. The fact is, I sold my car in 2008 and havenâ(TM)t looked back. One of the best decisions I made.
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Cars are such a burden, never mind their money pit nature.
I'm not against driving, and in fact I've got 3,000 km planned for our summer holiday in Turkey. But, I wouldn't want to drive my own car all the way across Europe before even doing that, and have the steering wheel on the wrong side for all of that ;). I foresee that I might need a car to run my son around to events when he gets a bit older, for which I hope a few years of membership to a car club will suffice. But day to day in the meanwhile, I'm
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Cars are such a burden
Not really.
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Of fucking course urban areas are more rich, they are like old factories that pollute right into the environment. Cities are more efficient exactly because they offload their externalities on people. So you get the horror shows like Tokyo or
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The cost is human misery: increasing density forces people to cram into ever-smaller, and ever-more-expensive apartments.
The fact is, people in cities are happier. Period, Across all surveyed countries and income groups.
The cost of not living in a city is misery.
That is separate from preference.
Using the example from one of your links, where 2/3rd of liberals say they would prefer to live in the city, and 2/3rd of conservatives would prefer to live outside of one, the fact of the matter is- both the liberals and conservatives are both happier in one.
As as I sa
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The fact is, people in cities are happier.
No. People in cities are _richer_. That's about it.
Using the example from one of your links, where 2/3rd of liberals say they would prefer to live in the city
See: brainwashing. Have you EVER heard a single liberal publication saying anything positive about suburbia? But now millenials are actually getting kids, and they started to realize that "advantages" of cities kinda don't exist. Especially for kids.
Trying to reframe the argument to "preference" vs the outlandish claim that "the cost of cities is human misery" isn't clever. It's transparent stupidity.
And you're transparently grasping for straws to support your ideology-driven drivel. E.g. you conveniently don't look at studies like this one: https://www.washingtonpost.com... [washingtonpost.com]
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No. People in cities are _richer_. That's about it.
Well, that too. But also happier. Polls confirm it.
You were wrong. Quite literally as wrong as you could get.
See: brainwashing. Have you EVER heard a single liberal publication saying anything positive about suburbia? But now millenials are actually getting kids, and they started to realize that "advantages" of cities kinda don't exist. Especially for kids.
lol, so now you're trying to handwave away the fact that you were wrong, and provably so, by saying it's brainwashing? We city folk are brainwashed into being happier than those not in the city?
And you're transparently grasping for straws to support your ideology-driven drivel. E.g. you conveniently don't look at studies like this one: https://www.washingtonpost.com... [www.washingtonpost.com] [washingtonpost.com]
First, don't be a dick. Don't share paywalled links.
That article is about Canada.
Actual study available here. [nber.org]
It was sourced from CCHS data collected and distributed by the Canadian government. You can rea
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Why on earth would housing prices be effected by new units of low density housing but not by new units of high density. Show some data.
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Re: Deck chairs on the Titanic (Score:3)
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Europe managed to control it to a degree (e.g. Copenhagen is the same population as in 70-s), but eventually the urbanist pro-misery lobby won.
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...but eventually the urbanist pro-misery lobby won.
I always find it amusing when someone assumes that just because they don't like something (in this case urban living) that no one does.
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Low density housing can be built in areas where the land is cheap.
Yes but high density housing is built vertically with units on top of other units so land use is minimal relative to the number of homes produced. This is literally what makes high density housing high density.
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So here's the thing, the ONLY way to lower the housing price (outside of Detroiting your economy) is to build NEW low-density cities.
Density and rising house prices have zero to do with each other. "Low density America" is having just as many problems as "high density Europe". Except that statement isn't a thing either since house prices are very region dependent, not country or continent dependent, and definitely not density dependent.
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Density and rising house prices have zero to do with each other.
Can you point just one example in the US or Europe of rising density resulting in lower prices?
not country or continent dependent, and definitely not density dependent.
It absolutely IS density-dependent. Increasing density results in higher housing prices. It's a pretty much universal phenomenon.
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Generally intersection changes don't increase capacity, since the surrounding roads don't change. A diverging diamond interchange smooths out traffic flow to only have perpendicular crossings or parallel merges. No right-hand turns which is a lot safer for cars as well as bikes/pedestrians, all while taking up the same number of lanes.
A DDI isn't something you'd place in a dense city, it's something that goes on a highway interchange
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I learned to drive *because* of my countries public transport system.
I was fed up of being crammed into standing-room-only (and even then, only just about) vehicles for every peak trip - whether that be my commute to work on the bus, or my cross-country train trip of 3 hours.
I was also fed up of busses going sailing past me at a stop, because they were already full, and the next bus being 30 minutes behind - and no additional capacity ever being added.
I was fed up of waiting on a train platform waiting for
Re: Deck chairs on the Titanic (Score:2)
The original "induced demand" paper was about intersections, not capacity. Idiots like you think it applies everywhere, and that zero road capacity is the best capacity.
Newsflash dumb-dumb: most of the traffic demand at rush hour is inelastic. People *have* to go to work. People *have* to send their kids to school. Adding road capacity won't magically split everyone into identical twins who now have to go to two jobs or send their kids to two schools simultaneously.
Re: (Score:2)
If you want both roads to be free flowing all the time, there are interchanges for that (there is even one just down the road where I66 meets US29) but they cost a lot more money.
Re:Why not just an overpass (Score:4, Informative)
Re: (Score:2)
>This design is elegant with only a small sacrifice in cognitive complexity for some users
There must be a lot fewer moronic drivers where you live. While I admire the theory, I'm pretty sure my neighbours would ensure any implementation of this would increase accident rates significantly.
Re: (Score:2)
The highway traffic doesn't stop at all.
If there is an intersection between two high speed limited access highways, then you need a cloverleaf, and no lights are needed, but they use a lot of land and there is expense in building multiple overpasses. This diverging diamond interchange is for a regular street or road intersecting the highway.
In the common diamond design, right turns are easy, but left turns cross oncoming traffic, so must be regulated by a light. That is inefficient, decreases vehicle thro