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Why are Texas interchanges so tall?

practical.engineering

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Re: Why are Texas interchanges so tall?

#81

Post by ajkjk »

h_tbob wrote: post #76

As 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? T…

I 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.

Re: Why are Texas interchanges so tall?

#82

Post by morsch »

pixl97 wrote: post #46
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.

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.

Park + ride

Re: Why are Texas interchanges so tall?

#83

Post by jader201 »

h_tbob wrote: post #76

As 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? T…

My 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.

Re: Why are Texas interchanges so tall?

#84

Post by oblio »

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.

During rush hour most people are going from their homes to places of employment, which are generally highly concentrated.

The "homes" part is distributed, true, but guess what, once you have a good rail network, it provides decent coverage for that (which you can complement via walkability/bikeability/scooterability :-p, which makes for more liveable environments). And "train commuter rage" is much less frequent than "road rage" plus a lot more people die or get maimed driving a car/getting hit by a car than they do because of trains.

Re: Why are Texas interchanges so tall?

#85

Post by kube-system »

msisk6 wrote: post #72
kube-system wrote: post #63

Earlier quoted context omitted.

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.

Being someone that has sat in a lot of traffic in Texas on these interchanges, the number of vehicles with more than one person is a rounding error. There's a few trucks hauling freight, but they try to miss the cities during rush hour.

> There's a few trucks hauling freight

There's a lot of trucks hauling freight. The US has the largest train network in the world, it notoriously handles primarily freight, and still, more than 70% of freight in the US goes by truck.

If these roads are the average urban interstate highways, then about 10%ish of the traffic is heavy truck traffic.

https://www.fhwa.dot.gov/policyinformation/statistics/2020/v...

Re: Why are Texas interchanges so tall?

#86

Post by oblio »

criddell wrote: post #59
estebank wrote: post #51

Earlier quoted context omitted.

You 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.

Well that's a problem. I'm not willing to pay anywhere near as much for public transportation as I am for a private vehicle and everything that goes with that. But I do think you are on the right track. I think public transportation in the form of buses doesn't make a lot of sense. But if Musk had been able to deliver on his promise of self-driving cars, then a giant city operated (or at least funded) fleet of small…

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.

Re: Why are Texas interchanges so tall?

#87

Post by oblio »

pixl97 wrote: post #46
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.

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 and they'll start demanding public transit.

However this whole path is killed via NIMBY.

Re: Why are Texas interchanges so tall?

#88

Post by Gud »

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…

Have you been to a city(and country) with a good public transport system? I live in Zürich(not from here) and it blows my mind how convenient it is to walk 25 meters to the nearest tram stop and easily get to anywhere in the city.

I used to think like you, that having car was a necessity, even freedom. Now I see it for what it is, a ball and chain.

Re: Why are Texas interchanges so tall?

#89

Post by morsch »

gullywhumper wrote: post #49

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

Loads of interchanges have Wikipedia pages: 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_D...

Re: Why are Texas interchanges so tall?

#90

Post by xyst »

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 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.

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