Capped freeeways in Austin? (Dallas, Howe: real estate, how much, earthquakes)

[LeoZ]

Over at the SkyscraperPage Forum and recently on the Downtown Austin Blog, people have been kicking around the idea of having a capped freeway (that is, for example, I-35 being covered with another layer on top of which would be more green development, whatever) in Austin. I just recently got wind of this so I'm not too sure of the viability, but what do y'all think?

[jobert]

Originally Posted by LeoZ

Over at the SkyscraperPage Forum and recently on the Downtown Austin Blog, people have been kicking around the idea of having a capped freeway (that is, for example, I-35 being covered with another layer on top of which would be more green development, whatever) in Austin. I just recently got wind of this so I'm not too sure of the viability, but what do y'all think?

I think it's a great idea and completely feasible *the kicker* with proper funding.

They've done it in Dallas and Boston, and there is always use for more parkland - always.

I-35 has turned into Austin's version of the Berlin Wall and it has to go for the sake of the city.

[austinnerd]

Hasn't Austin been kicking around the idea of "sinking" I35 through downtown for quite a while now. I'm not sure if this is what your referring to, since "capping" and using the space above it sounds almost like making it a tunnel. With the idea of "sinking" it, you'd gain a bit of real estate above if you cantalever / overhang the edge, but I'm not sure how nice of a space you'd be left with with all the cross roads and traffic noise.

That said, I completely agree that sinking the freeway would make for a far more aesthetically pleasing area than what currently exists. And if in the process, they fix the stinkin on/off ramps than all the better. Now whether or not it's worth the inevitable large cost and massive disruption to traffic for years is another story entirely.

[JayBrown80]

Originally Posted by LeoZ

Over at the SkyscraperPage Forum and recently on the Downtown Austin Blog, people have been kicking around the idea of having a capped freeway (that is, for example, I-35 being covered with another layer on top of which would be more green development, whatever) in Austin. I just recently got wind of this so I'm not too sure of the viability, but what do y'all think?

I would prefer them to put another highway on top of I35, we have more need of roads than of green space. And I am an enviornmentalist, so that Is hard for me to say.

But, No one wants to give up land for more roads, so where else to build but up?

[LeoZ]

Originally Posted by austinnerd

Hasn't Austin been kicking around the idea of "sinking" I35 through downtown for quite a while now. I'm not sure if this is what your referring to, since "capping" and using the space above it sounds almost like making it a tunnel. With the idea of "sinking" it, you'd gain a bit of real estate above if you cantalever / overhang the edge, but I'm not sure how nice of a space you'd be left with with all the cross roads and traffic noise.

That said, I completely agree that sinking the freeway would make for a far more aesthetically pleasing area than what currently exists. And if in the process, they fix the stinkin on/off ramps than all the better. Now whether or not it's worth the inevitable large cost and massive disruption to traffic for years is another story entirely.

From the pictures I've seen on the SkyscraperPage Forum, it would be kind of like making it a tunnel. It would be essentially putting a roof on top of the highway, and developing on top of that.

I'm a little unfamiliar with this "sinking" technique. How would that work?

Either way, I personally think either solution would be a lot better than what's there already. However, money is always an issue, as is the city's notoriously slow pace at getting proposals passes through the council.

[austinnerd]

Originally Posted by LeoZ

From the pictures I've seen on the SkyscraperPage Forum, it would be kind of like making it a tunnel. It would be essentially putting a roof on top of the highway, and developing on top of that.

I'm a little unfamiliar with this "sinking" technique. How would that work?

Either way, I personally think either solution would be a lot better than what's there already. However, money is always an issue, as is the city's notoriously slow pace at getting proposals passes through the council.

Picture the lower level of I35 without the upper level. If you've ever been there, the portion of 75 that runs through Dallas is sunken (as well as a few others). This generally keeps the freeway out of the sight line (and helps a bit with the sound), but really doesn't help much with the "divide" it creates. The plans are similar, the question is do you truly make a tunnel (or extensive overhangs), or leave it untopped (which would obviously be cheaper).

[thesonofgray]

This is a terrible idea for Austin's freeways. I'd love more green space, but making an at-grade freeway a tunnel, and then putting a "green roof" on top of it is more wasteful than it is environmentally beneficial.

Think about it. First, the cost would be incredible. The support structure would need to be substantial. Couldn't this money be used for something a little more effective? Second, tunnels are inherently less safe. Visibility is typically lower. You'd need extensive lighting plus mechanical ventilation, adding more upfront and continued maintenance costs.

It's just not a good idea. However, for those freeways that are already below grade and that have multiple overhead crossings that would be easy to span - this may feasible and costs may be reasonable.

I'm all for green space, but this isn't a cost effective way to get it.

[johnrex62]

The cost and emissions from the lighting and equipment to maintain a tunnel would certainly over reach the added green from a plant roof. The environmental equipment alone would release tons of emissions from the diesel powerplants required to operate the circulation fans or water pumps.

[thesonofgray]

But on the topic of making our freeways more "green", I really like what has happened (intentionally or not) to one section of the raised Hwy 183 near the Arboretum:

austin, tx - Google Maps

Why doesn't TxDOT or the City seed these sort of vines so they can cover the freeway retaining walls? The vines are much more appealing than the concrete wall (I'm sure some will think the exact opposite), although I doubt there's much, if any, "environmental" benefit.

[G Grasshopper]

Wouldn't it be extremely expensive to dig a tunnel of that length? Look at how much it costs to dig a swimming pool. Or perhaps that particular area isn't limestone, and has switched over to blackland, I don't know. At any rate, it seems that it would be more cost effective and probably more energy efficient to put a second level on the existing road. In an area that has rock substrate and not prone to earthquakes, it would seem like a better way to go. Of course, I'm no engineer, but just a thought.