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Comment by 0cf8612b2e1e | Hacker News Reader

I 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.

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The 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?"

That'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!

From 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.

Lots 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.

It'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.

The 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.

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