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Why are Texas interchanges so tall?

practical.engineering

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Re: Why are Texas interchanges so tall?

#61

Post by jnwatson »

dylan604 wrote: post #44
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.

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

Energy savings isn't the point though. The point is so that large trucks won't slow down traffic having lost a bunch of energy from braking to get on a cloverleaf.

Re: Why are Texas interchanges so tall?

#62

Post by TeMPOraL »

Scoundreller wrote: post #48
sroussey wrote: post #42

Earlier quoted context omitted.

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

Organic advertising? As in, showing prospective importers how cool it is to have abundance of $thing.

Re: Why are Texas interchanges so tall?

#63

Post by kube-system »

kuschku wrote: post #34
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.

Assuming the 500k people all commute between 6am-9am and 3pm-8pm, that means this interchange moves 160k people per hour. That's 1½-2½ commuter rail lines or about 3-4 subway lines. Such interchanges are truly a monument to stupidity.

That's 500k vehicles not 500k people.

While the plurality of vehicles could be single-occupant passenger vehicles, a good chunk of those vehicles are freight, multiple-occupant passenger vehicles, and some are even busses.

Re: Why are Texas interchanges so tall?

#65

Post by jnwatson »

robotnikman wrote: post #5

As cool as the engineering is, I avoid such interchanges at all costs since the being so high up gives me panic attacks when driving...

The first time I approached the High Five I got a pit in my stomach, and I'm not a particular anxious person. Its scale is astonishing.

Re: Why are Texas interchanges so tall?

#66

Post by panick21_ »

kube-system wrote: post #63
kuschku wrote: post #34

Earlier quoted context omitted.

Assuming the 500k people all commute between 6am-9am and 3pm-8pm, that means this interchange moves 160k people per hour. That's 1½-2½ commuter rail lines or about 3-4 subway lines. Such interchanges are truly a monument to stupidity.

That's 500k vehicles not 500k people. While the plurality of vehicles could be single-occupant passenger vehicles, a good chunk of those vehicles are freight, multiple-occupant passenger vehicles, and some are even busses.

The overwhelming majority of vehicles are single-occupant, specially during commute.

Re: Why are Texas interchanges so tall?

#67

Post by panick21_ »

WheatMillington wrote: post #57
kuschku wrote: post #34

Earlier quoted context omitted.

Assuming the 500k people all commute between 6am-9am and 3pm-8pm, that means this interchange moves 160k people per hour. That's 1½-2½ commuter rail lines or about 3-4 subway lines. Such interchanges are truly a monument to stupidity.

>That's 1½-2½ commuter rail lines or about 3-4 subway lines. Assuming every single commuter is coming from and going to the same place, sure.

Tell me you don't understand how rail network work without telling me you don't understand how rail networks work.

Re: Why are Texas interchanges so tall?

#68

Post by msisk6 »

tines wrote: post #14

I heard somewhere that the reason is to provide trucks the ability to shed speed to make these sharp turns, and then give them back their speed when coming back down so they don’t have to brake hard or spend a lot of gas to do it. Basically lets trucks use gravity to store their energy when making sharp turns and then get it back for nearly free.

Those steep ramps and banked curves sure are fun when an ice storm comes along about once every five years.

Re: Why are Texas interchanges so tall?

#69

Post by yongjik »

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…

Sounds like you experienced car vs. bus in a car-optimized city and liked the former, which is pretty understandable.

In a bus-optimized city, you'd be saying something like "Sure I can drive to work in 15 minutes, but it takes 5 minutes to park, costs $20 a day, and it's ten minutes walking from the parking lot to the office. Much better to take a bus that stops right across the street."

Re: Why are Texas interchanges so tall?

#70

Post by mrguyorama »

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…

>Still, to this layman it seems like a colossal engineering cost to build all those bridges and ramps for relatively modest gain.

IMO, maybe Texas does this because Texas gets a lot more taxes than they talk about (through high property taxes), and don't really want to spend them on anything else (like socialism!), so instead they build 10 lane highway systems for the billion cars and trucks every american should own.

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