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Why are Texas interchanges so tall?

practical.engineering

171–180 of 352 posts

Re: Why are Texas interchanges so tall?

#171
post #26

First time I visited the US it was Houston, Texas. My host was perplexed because I laughed out loud while we were driving. Experiencing highways and those massive gas stations felt like someone had made a state that mocked America by taking prejudices we have about the American traffic and making them 200% larger in real life. My mind was blown.

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Re: Why are Texas interchanges so tall?

#172

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…

I expect it's more because it's growth has been in modern times. Some planner liked frontage roads and set the fetish.

In areas where large highways were built over small highways, it isn't so easy to add an additional road.

Re: Why are Texas interchanges so tall?

#173
post #35

Earlier quoted context omitted.

It's because they let the same company design and build the interchange and own the concrete plant. "Design-build" project delivery. It is the same reason why the new HSR projects in California have ludicrous vertical and side clearance compared to other countries with better/cheaper HSR.

I don't follow, why they would increase their costs on purpose?

Who is they? The desingers charge to more for harder designs so the more it costs the more they make. Similar for the builders.

Re: Why are Texas interchanges so tall?

#174
post #35

Does anyone know why the flyover ramps in a stacked interchange usually have such large vertical clearances? The vertical separation seems much larger than necessary to accommodate the tallest trucks allowed on the highway. EDIT: There are some more theories here: https://engineering.stackexchange.com/questions/4238/why-are... Obviously there may be many contributing factors, but I expect one is dominant. This one is…

It's because they let the same company design and build the interchange and own the concrete plant. "Design-build" project delivery. It is the same reason why the new HSR projects in California have ludicrous vertical and side clearance compared to other countries with better/cheaper HSR.

design build works well for things they copy often. A design build house is your best deal on new construction. When things are unique costs blow up

Re: Why are Texas interchanges so tall?

#175

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…

The gain isn't "modest".

At a cloverleaf, the weaving between people entering a highway from one leaf and people trying to get onto the next leaf is an utter destroyer of traffic flow, especially when you add in some human behavior, where some people are assholes and won't let people merge in front of them, even when they're trying to merge to the other lane themselves.

Re: Why are Texas interchanges so tall?

#176

Earlier quoted context omitted.

The best analogy I've heard for explaining Texas to non-Americans is that Americans view Texans the same way the rest of the world views Americans.

>Americans view Texans the same way the rest of the world views Americans. Reversing some of the substrings in that string would also result in a very good analogy.

Like:

Texans view Americans the same way Americans view the rest of the world - derisively, but it is those viewers who should be derided, and often are, by the groups that they deride.

Re: Why are Texas interchanges so tall?

#177
i resent the default cynicism that is trendy when discussing highway infra. A clear bias against cars as ugly, dirty , polluting, etc.

This interchange provides food and prosperity to millions of people. And it's an incredible feat.

The cynical attitude is just cliche and tacky give it up.

Re: Why are Texas interchanges so tall?

#178
post #92
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…

It’s not about rural places. It’s about how cities are centered around car.

Cities in the us are basically highway with warehouse around it.

It’s hard to navigate without a car, and public transportation are a afterthought.

Re: Why are Texas interchanges so tall?

#179
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 see this "induced demand" critique a lot, and I am curious - if it's wrong, how is it different than adding housing to a region to make it cheaper?

You're right that it's not entirely different.

But I'll start with the simple version of the critique. Individual commuters make their decision about whether to make a trip based in part on the time that trip will take (a function of road congestion). Thus, adding road capacity will temporarily lower the cost of a trip, allowing more people to make it until congestion reaches the pre-expansion level. Housing does not have this problem because consumers make decisions about where to live much more infrequently.

As you can tell, "induced demand" is a bad if rather catchy name. To be fair to urban planners, the throughput of an expanded road does increase. However, the experience of using it stays the same or gets worse, and the cost (both $ and space) is disproportionate. Is the pro-transit argument, which I subscribe to.

Of course, the real world includes large real estate firms which are making frequent decisions on housing stock. So I agree that the build-more-housing-and-everything-will-improve crowd is wrong. But I don't think YIMBY/transit and anti-transit are the only choices. The former is a common archetype these days.

Re: Why are Texas interchanges so tall?

#180
post #138
post #26

First time I visited the US it was Houston, Texas. My host was perplexed because I laughed out loud while we were driving. Experiencing highways and those massive gas stations felt like someone had made a state that mocked America by taking prejudices we have about the American traffic and making them 200% larger in real life. My mind was blown.

Houston native here. I still guffaw when I see a massively lifted truck (but with a pristine bed, no scratches - so not even a work truck). Everything's bigger in Texas, including egos.

> Everything's bigger in Texas, including egos.

Crucially, Texans are highly aware of "everything is bigger in Texas" trope and take pride in it. My favorite example is that everyone knows that Texas State Capitol is taller than United States Capitol (92.24m vs 88m)... But nobody will ever tell you that Texas State Capitol is only 6th tallest state capitol.

Source: lived in Austin for 2 years.

https://en.wikipedia.org/wiki/Texas_State_Capitol#

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