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Why are Texas interchanges so tall?
- 0cf8612b2e1e 2y agoI only had a quick skim so far, but I did not feel like the article gave a firm enough rationale? I have seen scenarios in Texas when there is seemingly no other infrastructure or geography that could explain the over building.
- missingcolours 2y agoThe tl;dr to the article is "Texas freeways have frontage roads, which add at least one additional level to a traditional stack interchange, and that makes them taller than interchanges in e.g. California. The broader question I've always had, that's not addressed in the article, is "so why do California and Texas build so many stack interchanges while the rest of the country mostly does not?"
- beowulfey 2y agoThat's an interesting thought. Are there statistics out there for "percentage of interchanges that are stacks"? I've lived in CA and the Northeast. I didn't get the impression that either region uses them preferentially. Certainly I see them more in CA, but I feel like that is probably because the number of interchanges is higher, ha!
- seijiotsu 2y agoFrom the article: > And the design that generally provides the most capacity, on the smallest footprint, (often for the highest cost), is the stack. This would explain why there are plenty in coastal California, where there are tons of people to move around and where space is very much at a premium.
- devilbunny 2y agoLots of people, lots of highways, lots of land that wasn't occupied by houses and people 100 years ago. Pretty simple. Stack interchanges are very common for high-traffic areas, some of which wouldn't necessarily show up on your mental radar.
- nonameiguess 2y agoIt's addressed. The frontage roads by any reasonable measure seem like an objectively stupid idea that the state largely regrets building so much of, but they did it because it made it easier to acquire the adjacent land to build the highways. There may not be any infrastructure or geography that would have made building differently any harder, but the land had owners and Texas is probably abnormally deferential to private landowners as US states go.
- msisk6 2y agoThe frontage roads are great. If the freeway comes to a standstill you just cross over to the frontage road and continue. Doesn't matter if there's an exit or not. Everyone has giant 4x4 trucks so you can just exit where ever you want and hop on the frontage road. Eventually everyone does that and the frontage road gets clogged so timing is everything. Texas is interesting.
- Groxx 2y agoSo... > 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 shouldn't be relevant for high ones, it just raises many 1-high to 2-high. Or do they, in Texas? Or is it just that Texas has one famous one and people extrapolate that to mean the whole state is absolutely smothered in interchanges, until it looks like a scene from The Fifth Element?
- missingcolours 2y agoThere 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.
- mikepurvis 2y agoFrom 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 gain.
- seijiotsu 2y agoDon’t forget ease and safety. With a stack interchange (and many other types), you often have plenty of time beforehand to position yourself into the correct lane. But if you are going to go through a cloverleaf you will often need to make a stressful weave into the leaf, and then back again into the highway.
- 2y ago
- lwansbrough 2y ago> 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.
- mschuster91 2y agoAnd 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.
- criddell 2y ago> 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 can be dangerous.
- sroussey 2y agoI don’t live in a place where just walking around can be dangerous to my health.
- dylan604 2y agowell, aren't you special then. what's the point of this comment?
- estebank 2y agoYou need to compare not against what you currently have, but rather what you'd have if there was political will and budgets comparable to what was spent on the existing car infrastructure. Otherwise is saying that no-one wants a bridge to cross a river because no-one swims across.
- robotnikman 2y agoAs cool as the engineering is, I avoid such interchanges at all costs since the being so high up gives me panic attacks when driving...
- malshe 2y agoMe too! I can’t avoid them all the time but I slow down as much as I can safely (this is Texas so everyone drives at least 20 miles over the limit) and look straight ahead.
- msisk6 2y agoOnce I was cruising down the 130 toll road around Austin just after rush hour listening to the radio and just keeping up with traffic. Then traffic started pulling away from me and I couldn't keep up; my truck wouldn't go any faster. Thinking I was having a problem I looked at the dash and noticed I was going 105 mph and was up against the speed limiter on my truck. Yeah, even when the speed limit is 85 that's not enough for Texans. ;)
- malshe 2y agoAh 130 toll road! Yeah, I can totally imagine people zooming past you even when you were driving at 100+
- stevenwoo 2y agoNormally you are either going so fast you are looking far down the road and not over the side or really slowly, trying to not rear end the car in front of you, the height is not that noticeable unless one is a passenger. One time I was on a freeway in Houston at night and suddenly sparks started flying down on me while I was going at normal speed - it was a truck that had flipped on its side in the merge lane that was above me and to the left and was grinding against the road and the guardrail at about highway speed (for a little bit), that was a new fear unlocked.
- jnwatson 2y agoThe 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.
- 486sx33 2y agoPerhaps Texas is uniquely specialized in building “up” and in a compact space due to all the oil and petrochemical industries and specialized knowledge ? This offers financial efficiency in building these stacked interchanges that might not be so cost effective elsewhere ? I mean the less you move the cranes around the cheaper I’m sure
- jessriedel 2y agoDoes 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-flyovers-metro-rail-tracks-much-higher-than-traffic https://engineering.stackexchange.com/questions/4238/why-are... Obviously there may be many contributing factors, but I expect one is dominant. This one is most convincing to me: The flyover ramp generally needs to go over some things and under other things. Additionally, for both safety and rider comfort, the ramp needs to be vertically smooth, not having fast drops or rapid climbs. That means ramp A might pass over ramp B by a lot more than the minimum amount because ramp A also needs to pass over ramp C just a bit later, where it does so by a much lower amount. With many overlapping constraints like this, most ramp intersections are much higher than the minimum clearance even though none can be lowered without either (1) making one of the clearances below minimum or (2) forcing a ramp to rapidly climb/descent.
- function_seven 2y agoThis comment was posted the same time you asked your question, but I think it's one decent reason: https://news.ycombinator.com/item?id=41303428 https://news.ycombinator.com/item?id=41303428
- jessriedel 2y agoIt's an interesting theory, but ChatGPT was skeptical, and I can't find anything on the internet that supports it. Thanks for the pointer though.
- bob1029 2y agoPart of it may be due to constraints of the construction process itself (I.e. not disrupting existing traffic) I've never seen one built all at once. It's always a bunch of incremental changes over time.
- gosub100 2y agoI'm completely guessing, but maybe to prevent harmful oscillations from wind currents blowing between the roads?
- tines 2y agoI 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.
- lagniappe 2y agoNow THAT is some cool engineering I can get behind.
- 0cf8612b2e1e 2y agoThat 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.
- sroussey 2y agoIt’s Texas so you would assume they want people to waste gas.
- Scoundreller 2y agoI thought they wanted to sell it to other states Never understood when major exporters of $thing would also specifically heavily subsidize $thing
- TeMPOraL 2y agoOrganic advertising? As in, showing prospective importers how cool it is to have abundance of $thing.
- dylan604 2y agoI'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
- freitzkriesler2 2y ago[dead]
- nabla9 2y agoFirst 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.
- bravetraveler 2y agoI grew up in Appalachia and moved to Texas as an adult. Very similar experience, ride-laugh and all. This place is both amazing and ridiculous.
- hoten 2y agoHouston 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.
- psunavy03 2y agoThe 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.
- hoten 2y agoI'll accept that. Somehow I forgot to mention truck nuts. Car culture is something else entirely in Texas.
- throwup238 2y agoTruck nuts? https://smartcdn.gprod.postmedia.digital/driving/wp-content/uploads/2019/07/trucknuts-1.jpg https://smartcdn.gprod.postmedia.digital/driving/wp-content/...
- hoten 2y ago
- gosub100 2y agoI remember reading a long form article on HN about 2 years ago that was about Texas roads and highways. It wasn't from practical engineering though. Maybe it was the website of the guy who Grady briefly mentions in his video?
- gullywhumper 2y agoI 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 https://en.wikipedia.org/wiki/High_Five_Interchange
- aidenn0 2y agoOne close to where I grew up with its own page is the Springfield, VA interchange[1][2]. 24 lanes wide at its widest point. 1: https://en.wikipedia.org/wiki/Springfield_Interchange https://en.wikipedia.org/wiki/Springfield_Interchange 2: https://www.openstreetmap.org/#map=17/38.791557/-77.175887 https://www.openstreetmap.org/#map=17/38.791557/-77.175887
- morsch 2y agoLoads of interchanges have Wikipedia pages: https://en.m.wikipedia.org/wiki/List_of_road_interchanges_in_the_United_States https://en.m.wikipedia.org/wiki/List_of_road_interchanges_in... I think literally every interchange in Germany has got its own article: https://de.m.wikipedia.org/wiki/Kategorie:Autobahnkreuz_in_Deutschland https://de.m.wikipedia.org/wiki/Kategorie:Autobahnkreuz_in_D...
- Animats 2y agoFrontage roads force a design decision. Texas likes to run the frontage roads through the interchange ramps. California generally displaces the freeway about 200m from major surface roads to avoid running the surface street through the ramps. CA-92 at US-101 does that. When too many layers are needed, CALTRANS often goes for a tunnel underneath. See CA-92 at I-280, and SF's 19th Avenue at I-280. At US-101 and I-280 in San Francisco, a frontage road does go through the ramps. The interchange was spread out horizontally to avoid piling up all the levels.
- riffic 2y agocompensation (it's a psychological concept) https://en.wikipedia.org/wiki/Compensation_(psychology) https://en.wikipedia.org/wiki/Compensation_(psychology)
- deleted 2y ago[deleted]
- h_tbob 2y agoAs somebody who lived in Dallas and drove on the high five with some frequency, I had actually a lot of questions about the design of it. If somebody who understands this could explain I’d be happy. For one, a lot of the overpasses had two lanes. But then they merged down to one right before you got on the highway… What’s the point in having two lanes on the overpass that merge just before you get onto the highway? There was always slow traffic because of this. If it was me, I would always make it so that you lose equal number of lanes To the outgoing overpasses as you will get in incoming overpasses to prevent inefficient lane changes. So if you have six lanes, you get 4 branch off, 2 for each direction on the other highway and keep 2. Then you get the four back from the intersection. No lane change. But the way they have it, there’s so much merging it , which is harder to drive, and I’m not sure it’s more efficient. Any thoughts?
- Neywiny 2y agoThere's a cities skylines YouTuber who agrees with you. He calls it lane math. "2 come off, 2 go on,..." I'm sure there's some reason the engineers do it irl, but it is funny that going with your approach does fix things in game.
- ajkjk 2y agoI wonder if it's more about having room for emergency vehicles or for people to pull over if there's an accident without totally stopping traffic.
- jader201 2y agoMy guess is the two lanes merging into one are only getting one lane. That is, only one lane is added after the merge, and both overpass lanes are merging into the one new lane. But if there are indeed being two lanes added due to the merge, agree that doesn’t make much sense. If the former, also agree that they should’ve added two lanes instead of one. But that decision could’ve come down to physical limitations, cost, or something else.
- cornstalks 2y agoI have no answer, but this got me thinking: is the overpass's road a similar physical width as the highway? I've been on some bridges that have two lanes with a very narrow shoulder that then then merge into a single lane (with wider shoulders) at the end of the bridge, with the asphalt width not changing too much. I've always assumed that was so traffic could continue flowing on the bridge should one lane become blocked for some reason. Off the bridge a car can pull off the road if there's a problem to let traffic continue passing. You can't really do that so much on a bridge. But I'm not a traffic/road engineer so that's just speculation on my part.
- xyst 2y agoIt’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 suburbs fill up. Geniuses at the state transportation department believe we should just widen the roads. But continue to ignore decades of “induced demand” evidence.
- pc86 2y agoI'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 want to live in a major urban area. You can't have a huge geography and rural or suburban life without private vehicles. [0] https://pubmed.ncbi.nlm.nih.gov/7892359/ https://pubmed.ncbi.nlm.nih.gov/7892359/
- yossi_peti 2y agoIf people want to live in rural areas, that's fine by me. They don't particularly contribute to the problems with car-centric infrastructure in the US. The main complaints are how most cities in the US are designed in ways that are hostile to anybody who doesn't have a car, such as: - making it difficult to get around safely by bike - zoning restrictions that force development to be clumped in certain areas - underdeveloped public transport with infrequent stops and limited range - parking space requirements that limit development - food deserts where people have to drive long distances to get groceries There are many places in the world that have solved these problems. I don't get why it's so inconceivable to solve them in the US.
- bamboozled 2y agoJapan is awesome like this, they have amazing highways and rail. Tokyo in my option is a bit too car friendly but it’s still very walkable and rideable.
- aj7 2y agoThe same reason that the ULA launch system costs more than SpaceX. Cronyism.
- brcmthrowaway 2y ago[flagged]
- deleted 2y ago[deleted]
- DidYaWipe 2y ago"the worst symbol of our car-obsessed culture" Nothing against the article, which covers an interesting topic. But this refrain gets tiresome, the railing against our "car obsession." We have a big-ass country. We like to move about it. Many of us don't want or need to live on top of each other. That is all.
- psunavy03 2y agoThere is also a subset of people who will go out of their way to dunk on Texas. I'm not Texan myself and feel the place has its pluses and its minuses (some of them huge ones on both sides of the ledger). But sometimes I'm like "come on, really, that's a cheap shot."
- mcbutterbunz 2y agoI'd just love some zoning changes that would allow light commercial in the middle of some neighborhoods so I don't have to drive miles to get a cup of coffee. Could be as simple as adding more pathways between neighborhoods so I don't have to ride my bike on a busy street and almost get hit by someone on their phone. Its not that we're obsessed with cars, its that cars are the only option for reasonable, safe transportation right now.
- heartbreak 2y ago> I'd just love some zoning changes that would allow light commercial in the middle of some neighborhoods This describes reality in Houston, and I do not get the impression that you’d like Houston at all.
- delta_p_delta_x 2y ago> We have a big-ass country. We like to move about it. Many of us don't want or need to live on top of each other. That is all. Japan is about the size of the entire Eastern Seaboard. Japan has safe, fast, comfortable and competitively-priced high-speed rail through highly mountainous, earthquake-prone terrain. What's the USA's excuse? No one is asking for a 4500 km-long railway from Los Angeles to New York. But a 1500 km-long one from Atlanta to Boston? Nope, can't do. Forget that, not even a 700 km-long one between Washington DC, New York, and Boston (where many people arguably 'live on top of each other' already). The US has no political will to up its public transport game, and your comment epitomises it.
- ljsprague 2y agoIt's because they don't have earthquakes.
- hoten 2y agoI recall seeing a regional breakdown on what different parts of the US call the frontage road. Fun fact, apparently the Houston area is the only place that uses the term "feeder road" (or just "the feeder"). In fact, being from Houston, I'm pretty sure most people wouldn't know what you meant if you said frontage road. It's that pervasive.
- fuzztester 2y agoOkay, <rolls up sleeves> ... From the OP: >They say everything’s bigger in Texas Me say: $ echo "They say everything’s bigger in Texas" | sed 's/They/Texans/' | sed 's/bigger/biggest/' echo ", including their egos."
- tonymet 2y agoi 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.
- Ylpertnodi 2y ago...just wait til you see this about North American (US and Canada) firetrucks: https://youtu.be/j2dHFC31VtQ?t=21 https://youtu.be/j2dHFC31VtQ?t=21
- tonymet 2y agothank you for sharing I found this entertaining and cringe-worthy
- jaccarmac 2y agoAfter browsing these comments, I would like to encourage fellow Dallasites to read László Krasznahorkai's short story "Nine Dragon Crossing", available in the collection The World Goes On. It's the most accurate thing I've read about being human amidst our freeways.
- drewcoo 2y agoVideo by that guy. Again. Am I honestly the only one who wants to see a video of him getting punched in the face? He really needs to be punched in the face.
- nealmueller 2y agoAnswer to headline: They rise so high to save some space, while keeping traffic flowing at a steady pace.
- glzone1 2y agoWhile the article complains about cars one challenge is simply the government's ability to reasonably operate transit - this includes things like keeping anti-social riders off it, keeping it quasi-pleasant to ride / safe / on time / not ruinously expensive.
- SebFender 2y agoWe had a few great examples around Montreal when finally someone's brain kicked in and were removed and changed for better solutions - at what cost... well there's a great question.
- CodeWriter23 2y ago> it’s kind of atrocious, right? I can’t take an engineering article seriously when it leads in with bias-revealing invectives. Does EVERYTHING have to be politicized?