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Why are Texas interchanges so tall?

practical.engineering

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Re: Why are Texas interchanges so tall?

#121

Post by tofof »

dylan604 wrote: post #38
mikepurvis wrote: post #24

Earlier quoted context omitted.

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…

The TFA specifically covers this, so skimming wikipedia should have been totally unnecessary. In fact, the TFA goes further than your wiki skim to add that the merging from the highway to the clover leaf requires slowing down on the highway while entering the highway from the clover requires accelerating. Both of these things are being done in the same piece of road. It does so with graphic animations. You'd probably…

This comment is misleading; the youtube video contains these animations but "the fucking article" does not. Please, if you're going to imply criticism that the article went unread, don't mention things that are instead in a video. The url attached to this post is to an article (a transcript), not to https://www.youtube.com/watch?v=-16RFXr44fY which contains the content you're talking about.

Instead, please consider helpfully linking to the animations[1] you're talking about, so that others can find them without having to waste time listening to content they already read.

1: https://youtu.be/-16RFXr44fY?t=185

Re: Why are Texas interchanges so tall?

#122

Post by lelandbatey »

pc86 wrote: post #92
xyst wrote: post #90

It’s a shame this country is so obsessed with cars. There’s so much land yet we devote it to destroying lush ecosystems (that help reduce effects of Mother Nature) and replacing it with massive highway projects that end up costing everyone more in taxes/indefinite maintenance costs. Then the effect is 10X’d when useless suburbs are built. More car dependence. More time spent on roads. Traffic slows to a halt as subur…

I'm not sure what you think the alternative is. The US is huge compared to any similarly developed country. Is the answer huge cities right next to thousands of square miles of untouched nature? That hasn't happened in any society on the planet. It sounds like you just want everyone to live in a city and take public transit everywhere but cities are awful for your mental health[0] and most people in the US do not wan…

The US being huge has no bearing on the requirement that I have to own a car to get to work every day, or to go to the grocery store, or to take kids to school. I live in a more suburban area than I used to and having to pilot a huge deadly vehicle everywhere is vastly more stressful than just walking to handle my groceries.

Note that the study you link to there is from 1994 and only controlled for the following criteria: sex, age, social class, marital status, unemployment, chronic illness and region of residence. Those aren't the things that put folks on edge about cities in 1994 or in the preceding years. 30 years on from 1994 and now in a different world, many of us are wondering why we're locked out of some of the benefits of a bit more density.

No ones saying we abandon all beyond our city walls to nature, instead they'll be farmland or productive rural activities like we already use them for. But we don't need every city of 500k people to mean that there's a 15 mile radius circle of strip malls in every direction.

Re: Why are Texas interchanges so tall?

#123

Post by vel0city »

bsder wrote: post #109
oblio wrote: post #86

Earlier quoted context omitted.

Self driving cars don't solve high traffic volumes. Cars just can't move enough people per hour, I think the average lane can move about 1800 cars per hour and most people don't share rides unless forced to. So that means about 1800-2500 people per hour per lane. A decent subway moves about 20 000 people per hour per line, I think. Cars are low to medium density transport, at best.

> most people don't share rides unless forced to. That wasn't true in the past. My father used to carpool with other teachers for 20+ years. I remember a lot of carpooling through the 1980s and into the mid 1990s where it fizzled out. I would suggest, however, that self-driving cars would be fine for carpooling. Most people would have no problem carpooling with a self-driving car if it always picked up the same bunch…

People got into carpooling because of the oil crises. Then the oil glut happened, things got cheap again, those carpool groups broke up, and it became uncommon again.

Re: Why are Texas interchanges so tall?

#124

Post by bamboozled »

xyst wrote: post #90

It’s a shame this country is so obsessed with cars. There’s so much land yet we devote it to destroying lush ecosystems (that help reduce effects of Mother Nature) and replacing it with massive highway projects that end up costing everyone more in taxes/indefinite maintenance costs. Then the effect is 10X’d when useless suburbs are built. More car dependence. More time spent on roads. Traffic slows to a halt as subur…

[flagged]

Re: Why are Texas interchanges so tall?

#125

Post by vel0city »

oblio wrote: post #87
pixl97 wrote: post #46

Earlier quoted context omitted.

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.

Well, there are solutions but then you get into even uglier politics. Allow higher density housing to be built without opposition (for example up zoning 1 level should be automatically approved: single family home can be torn down to build a duplex, etc). Then reduce and remove parking requirements. Once that's done density will just go up on its own and... cars don't scale. Traffic will absolutely murder everyone an…

Careful what you wish for. You have to wish the whole wish otherwise the monkey's paw will get you. Wishing for higher density without also pushing for better zoning policies overall will just make the traffic another level of pain, which is something seen in a number of cities. Sure, we'll then just build massive apartment complexes, one right next to the other. Where's the grocery store though? Where do these people work? Oops.

I see so many new residential projects with small lots or apartments. That's great! But still the zoning forces just housing, so its just homes on homes on homes for miles.

Re: Why are Texas interchanges so tall?

#126

Post by consp »

jcfrei wrote: post #120
xyst wrote: post #90

It’s a shame this country is so obsessed with cars. There’s so much land yet we devote it to destroying lush ecosystems (that help reduce effects of Mother Nature) and replacing it with massive highway projects that end up costing everyone more in taxes/indefinite maintenance costs. Then the effect is 10X’d when useless suburbs are built. More car dependence. More time spent on roads. Traffic slows to a halt as subur…

The US Highway building industry is in many ways a form of a state run social system. First of all the road construction and maintenance uses a huge amount of tax dollars and redistributes it to lower class construction site and road maintenance workers and some engineering bureaus. Secondly it gives everybody equal (highway) transportation access by continuously expanding capacity on existing roads and building new…

Poor people should not have to buy a car as it is a massive drain on finances to keep it running. There are better solutions

Re: Why are Texas interchanges so tall?

#127

Post by vel0city »

mrguyorama wrote: post #70
mikepurvis wrote: post #24

Earlier quoted context omitted.

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…

One-third of the Texas DPS highway budget comes from federal sources.

Another third comes from revenues from oil & gas.

About a quarter comes from state gasoline sales tax and registration taxes.

So a little more than 90% of the funding for freeway projects in Texas comes from non-property tax sources.

But even then, a lot of the recent major highway projects in Texas had some kind of toll component to them whether that just directly be toll roads or tolled "express lane" projects which often have parts of those toll revenue backed bonds going to fund things like highway interchanges and on/off ramps for the freeways.

The vast majority of the property taxes I pay go towards the schools, the public parks, the fire/police/public service, libraries, and local roads. City+County taxes are ~0.710%, just the ISD and community college is ~1.16%. A massive chunk of those city/county taxes are roads and public service people, with a bit of parks department and other things like that thrown in.

The state gets its cut mostly by sales taxes though. 6.25% is the state sales tax, with things like groceries exempted. Cities can levy up to 2% additional, for a max rate of 8.25%. Of that 2% my city levies, half of that goes to public transit.

Re: Why are Texas interchanges so tall?

#128

Post by jcranmer »

missingcolours wrote: post #7
Groxx wrote: post #3

So... > Q: Why are Texas interchanges so tall? > > Frontage roads need grade separation, adding a layer. > Texas has lots of frontage roads. OK, I buy that Texas has more grade-separated interchanges on average... but I'm not seeing how that turns into "Texas has more higher interchanges" which is what it feels like that question is asking. Frontage roads don't generally exist where 3+ highways intersect, so that sho…

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.

Frontage roads don't necessitate a lot of extra levels. Take the Circle Interchange in Chicago: https://en.wikipedia.org/wiki/Jane_Byrne_Interchange

It's an interchange that's tucked into the normal street grid of Chicago, taking up about 4 city blocks total, and requiring just 3 levels of bridges to get all the traffic to their destinations. The trick is that it relies on a windmill interchange rather than a stack (so the left turns aren't crossing each other in the center), and the Congress Parkway-into-Eisenhower Expressway goes from elevated highway to sunken highway over the course of the interchange. There's even a subway line in the middle of the interchange!

I think the better explanation is that the size of highway interchanges in Texas aren't meaningfully constrained, so there's little pressure to find ways to squeeze in more compact interchanges. Furthermore, I think Texas is motivated to make its interchanges high-speed--the highways look designed for a 65/70 mph speed limit, even near the city core, whereas the Kennedy Expressway near the Circle interchange drops down to 45 mph partially to deal with the confusion of the road (there are exits 51B-J on I-90 in this stretch, yes, that many exits in a single mile of road).

Re: Why are Texas interchanges so tall?

#129

Post by massysett »

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.

Heh, I read the numbers before your last statement and drew the opposite conclusion: if the interchange is moving as many cars as 4 subway lines, seems a bargain, especially as subways are expensive and have much more limited networks than roads.

Re: Why are Texas interchanges so tall?

#130

Post by jcfrei »

consp wrote: post #126
jcfrei wrote: post #120

Earlier quoted context omitted.

The US Highway building industry is in many ways a form of a state run social system. First of all the road construction and maintenance uses a huge amount of tax dollars and redistributes it to lower class construction site and road maintenance workers and some engineering bureaus. Secondly it gives everybody equal (highway) transportation access by continuously expanding capacity on existing roads and building new…

Poor people should not have to buy a car as it is a massive drain on finances to keep it running. There are better solutions

Theoretically yes but a lot would need to change for that to happen in the US. In reality having a car and traveling lots of miles every day is the cheapest variant for most people.
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