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Why are Texas interchanges so tall?

practical.engineering

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Re: Why are Texas interchanges so tall?

#41

Post by [deleted] »

mikepurvis wrote: post #24
missingcolours wrote: post #7

Earlier quoted context omitted.

There are frontage roads at most freeway interchanges in Texas. Typical stack interchange elsewhere has 4 levels: freeway 1, freeway 2, freeway 1 left turns, freeway 2 left turns. Frontage roads add 5th and occasionally 6th levels. The other thing not mentioned is the proliferation of separate express lanes, which often have dedicated flyover ramps as well.

From a quick skim of Wikipedia, it looks like the main benefit to the stack style over a conventional 2-level cloverleaf is capacity (the left-turn leaves are generally at most one lane) and speed (left turns are direct rather than 270deg, so you don't have to slow down as much when taking them). Still, to this layman it seems like a colossal engineering cost to build all those bridges and ramps for relatively modest…

[deleted]

Re: Why are Texas interchanges so tall?

#42

Post by sroussey »

0cf8612b2e1e wrote: post #28
lagniappe wrote: post #21

Earlier quoted context omitted.

Now THAT is some cool engineering I can get behind.

That sounds like tens of millions in extra infrastructure costs so as to save trucks a tiny amount of gas. It is Texas, so anything is possible.

It’s Texas so you would assume they want people to waste gas.

Re: Why are Texas interchanges so tall?

#43

Post by pixl97 »

stetrain wrote: post #20
lwansbrough wrote: post #4

> 37 bridges and more than 700 columns are crammed into this one spot to keep the roughly half a million vehicles flowing in every direction each day Truly pitiful numbers for a project of this scale lol.

And in the video the quote about keeping traffic flowing is laid over footage where the traffic is nearly stopped and creeping through the interchange.

Before this exchange 635 was just stopped around 5pm. That is part of the problem is you fix one spot and it move the pinch point down to the next exit.

Re: Why are Texas interchanges so tall?

#44

Post by dylan604 »

0cf8612b2e1e wrote: post #28
lagniappe wrote: post #21

Earlier quoted context omitted.

Now THAT is some cool engineering I can get behind.

That sounds like tens of millions in extra infrastructure costs so as to save trucks a tiny amount of gas. It is Texas, so anything is possible.

I've never heard of the proposed gravity assist theory in any discussion of these interchanges. Does it happen? Sure. Is it one of the reasons behind the design or just something that happens to also be true is the actual question. Pontificating on the interwebs is fun

Re: Why are Texas interchanges so tall?

#45

Post by sroussey »

criddell wrote: post #32
mschuster91 wrote: post #18

Earlier quoted context omitted.

And now imagine that these 500k people would be served by a decent network of trains or even buses. That would immediately reduce the demand for infrastructure, simply because how much more efficient even a single decker bus is in passengers/m² of occupied road space.

> more efficient Depends on what you are optimizing for. I can drive to work in 15 minutes, door-to-door. I used to ride the bus and sometimes I would be waiting that long just for the bus to appear. The other factor is weather. Not many of the bus shelters around me (I’m in Austin) are air conditioned. Right now it’s 103F / 39C with a feels-like temperature of 107 / 42. Depending on your health, just walking around…

I don’t live in a place where just walking around can be dangerous to my health.

Re: Why are Texas interchanges so tall?

#46

Post by pixl97 »

mschuster91 wrote: post #18
lwansbrough wrote: post #4

> 37 bridges and more than 700 columns are crammed into this one spot to keep the roughly half a million vehicles flowing in every direction each day Truly pitiful numbers for a project of this scale lol.

And now imagine that these 500k people would be served by a decent network of trains or even buses. That would immediately reduce the demand for infrastructure, simply because how much more efficient even a single decker bus is in passengers/m² of occupied road space.

Hello, texan here. No busses would do nothing for these people... pretty much the entire DFW area is surrounded by huge areas of low density suburbs. The busineses and locations these people are going to covers hundreds of square miles.

Car culture builds car cities. Once you have a car city it's nearly impossible to fix it... it's too big and expensive and low density to fix.

Re: Why are Texas interchanges so tall?

#47

Post by dylan604 »

mschuster91 wrote: post #18
lwansbrough wrote: post #4

> 37 bridges and more than 700 columns are crammed into this one spot to keep the roughly half a million vehicles flowing in every direction each day Truly pitiful numbers for a project of this scale lol.

And now imagine that these 500k people would be served by a decent network of trains or even buses. That would immediately reduce the demand for infrastructure, simply because how much more efficient even a single decker bus is in passengers/m² of occupied road space.

Now imagine you've designed said trains or buses lines. Where did you put them? How much money did it cost? How many people use them now that they are built? Please, enlighten us with how much better you are than those that are currently in place that have tried and failed.

Re: Why are Texas interchanges so tall?

#48

Post by Scoundreller »

sroussey wrote: post #42
0cf8612b2e1e wrote: post #28

Earlier quoted context omitted.

That sounds like tens of millions in extra infrastructure costs so as to save trucks a tiny amount of gas. It is Texas, so anything is possible.

It’s Texas so you would assume they want people to waste gas.

I thought they wanted to sell it to other states

Never understood when major exporters of $thing would also specifically heavily subsidize $thing

Re: Why are Texas interchanges so tall?

#49

Post by gullywhumper »

I lived in Dallas for a couple years, and while driving the Hive Five interchange (mentioned in the article) always seemed a little crazy, what really blew my mind was that a specific interchange could warrant its own Wikipedia page. For some reason that more than anything else really underscored its scale.

https://en.wikipedia.org/wiki/High_Five_Interchange

Re: Why are Texas interchanges so tall?

#50

Post by dylan604 »

sroussey wrote: post #45
criddell wrote: post #32

Earlier quoted context omitted.

> more efficient Depends on what you are optimizing for. I can drive to work in 15 minutes, door-to-door. I used to ride the bus and sometimes I would be waiting that long just for the bus to appear. The other factor is weather. Not many of the bus shelters around me (I’m in Austin) are air conditioned. Right now it’s 103F / 39C with a feels-like temperature of 107 / 42. Depending on your health, just walking around…

I don’t live in a place where just walking around can be dangerous to my health.

well, aren't you special then. what's the point of this comment?
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