Another I-35 Alternative through Austin? (drawing enclosed)

[thisdj78]

When I was in Houston, I noticed on the Sam Houston Toll South, how they are expanding the tollway by adding on width to the existing bridges. I was wondering if something similar could be accomplished with I-35 in Austin on the elevated sections?

Here's a picture below (sorry for the rough job):

The red section in the middle would be the addition with 4 new lanes (2 each direction). There's very little room on the lower deck so the lanes would have to utilize the median for a single post support and tie into the beams on the existing deck.



So essentially the lower deck would be completely covered. The challenge then is how these lanes merge back together at grade level on either end of the deck. Also, there would still need to be solution to the back ups between the split and Riverside, which could probably be accomplished by eliminating some of the ramps downtown.

[US81]

It certainly looks like a solution that would cause the least disruption to this non-engineer. 

[thisdj78]

It certainly looks like a solution that would cause the least disruption to this non-engineer.

The other tough part would be how to construct the center supports while still utilizing the lower deck, so my first thought is to shut down the middle lanes and temporarily convert the lower deck into a single HOV lane each direction. Then re stripe the upper decks for 3 lanes if space allows.

[Revive 755]

The other tough part would be how to construct the center supports while still utilizing the lower deck, so my first thought is to shut down the middle lanes and temporarily convert the lower deck into a single HOV lane each direction. Then re stripe the upper decks for 3 lanes if space allows.

Looks to me that the center section overhangs the outside lanes enough that the lower level would have to be completed closed during construction.

For the tie in at the south end, the lower level should swing outward from the centerline, pass under the ramps to/from Martin Luther King, before swinging back in to merge with the upper level lanes.  The ramps to/from 15th may need to be closed.

The north end looks like the upper level lanes would need to swing outward - looks like ROW acquisition would be required. 

[thisdj78]

The other tough part would be how to construct the center supports while still utilizing the lower deck, so my first thought is to shut down the middle lanes and temporarily convert the lower deck into a single HOV lane each direction. Then re stripe the upper decks for 3 lanes if space allows.

Looks to me that the center section overhangs the outside lanes enough that the lower level would have to be completed closed during construction.

This is true, so I imagine that the center column work could be done during the day with the lower deck inner lanes closed and then overhead work done overnight with the lower deck completely closed.

For the tie in at the south end, the lower level should swing outward from the centerline, pass under the ramps to/from Martin Luther King, before swinging back in to merge with the upper level lanes.  The ramps to/from 15th may need to be closed.

I agree

The north end looks like the upper level lanes would need to swing outward - looks like ROW acquisition would be required.

I'm wondering if the ROW around the Airport intersection could be used for this? The other solution is that maybe the lower deck is only used as HOV downtown express lanes after the above project, with one lane entrances at the north and south end and the outer lanes become merge lanes between 38th and Manor rd. Attached is a drawing of what I'm envisioning assuming the 8 lanes continue overhead beyond the red line:

[Alps]

I've done some staging work - no, you don't have to close the lanes completely. You can build deck sections off-site and bring them into positions overnight. You'd have to close the roadway completely overnight and lift in as many sections as you can, but at least that lets you have the full capacity when it's actually needed.

[codyg1985]

One problem I see with this is that there is very little room in the median of the lower level to accommodate bridge piers: http://goo.gl/maps/uuOgv

You may have to do "flying supports" where the columns are located on either side of the lower level and a large beam supports the expanded roadway.

[longhorn]

And you guys are forgetting this is Austin, the city council would never go for this for aesthetic reasons. There is a reason why the city is keen on sinking I-35. Back in the 80s when TXDot rebuilt 35 from Round Rock to 183, they shoul have added more than just ONE lane.

[thisdj78]

One problem I see with this is that there is very little room in the median of the lower level to accommodate bridge piers: http://goo.gl/maps/uuOgv

You may have to do "flying supports" where the columns are located on either side of the lower level and a large beam supports the expanded roadway.

True, I never considered that. With the single column concept, I figured that the shoulder would have to be sacrificed a little bit or go with a single lane HOV each direction to allow for it.

[thisdj78]

And you guys are forgetting this is Austin, the city council would never go for this for aesthetic reasons. There is a reason why the city is keen on sinking I-35. Back in the 80s when TXDot rebuilt 35 from Round Rock to 183, they shoul have added more than just ONE lane.

The tunnel concepts I've seen, still keep the decks and start the tunnel at 15th street, which means you will still have capacity issues north of 15th. I could be wrong but I haven't seen a seriously considered proposal that addresses the decks.

[Anthony_JK]

I'm just waiting for some New Urbanist anti-freeway radical to intervene and call for simply ditching the double deck and everything else, converting I-35 to an 8-lane surface boulevard with continuous flow intersections replacing all the interchanges, and re-routing I-35 via SH 45 SE and SH 130 (or even I-10 E of San Antonio and SH 130 from Luling northward.

*ducking for cover* 

[Brandon]

Damn!  I just looked at the Google Streetview for this thing (as it exists currently).  What a different setup.  Is one of the sets of lanes the express lanes, and the other the local lanes?

[US81]

Damn!  I just looked at the Google Streetview for this thing (as it exists currently).  What a different setup.  Is one of the sets of lanes the express lanes, and the other the local lanes?

Functionally, yes, sort of. There are a few exits served only by the lower deck, and one only by the southbound upper deck, IIRC. The segment is not very long and the signage (unless it's changed recently) shows two signs with different street names under two I-35 and two US 290 shields with two different exit number ranges as tabs over the BGSs.

I love the lower deck for the old highway architecture (unchanged from photos from the 1970's), but it is markedly different than the rest of I-35, with nearly non-existent entrance and exit lanes, no shoulder, and poor line-of-sight.

[longhorn]

Damn!  I just looked at the Google Streetview for this thing (as it exists currently).  What a different setup.  Is one of the sets of lanes the express lanes, and the other the local lanes?

Functionally, yes, sort of. There are a few exits served only by the lower deck, and one only by the southbound upper deck, IIRC. The segment is not very long and the signage (unless it's changed recently) shows two signs with different street names under two I-35 and two US 290 shields with two different exit number ranges as tabs over the BGSs.

I love the lower deck for the old highway architecture (unchanged from photos from the 1970's), but it is markedly different than the rest of I-35, with nearly non-existent entrance and exit lanes, no shoulder, and poor line-of-sight.

Yet,if you want to get through the split with the least problems and quick, stick to the left lane and take the lower level.

[Anthony_JK]

One question that I have: wouldn't a "cut and cappped" section not fit very well with the double decked segment at all due to a severe transition in grade from the upper decked section to the "capped" section?

Personally, I'd either do one of two things:

1) Do away with the upper decks entirely, widen the depressed section to 8 lanes, and add frontage roads on each side to serve local traffic, eliminating the exits entirely (you could even cantilever the frontage roads over the mainline to save ROW, and use the median for express lane connections to US 183/US 290 or HOV lanes);

or 2) Keep the upper decks, widen them to 10 lanes, and convert the lower deck to HOV/Bus lanes with local exits, perhaps even connecting them with the proposed frontage roads for local access. Perhaps, the upper deck lanes can even be extended N to 183/290 while the frontage roads can serve as a "boulevard and freshened using the same Context Sensitive Solutions design methods proposed in the "cut and cap" proposal.

Just winging some suggestions around...

[thisdj78]

or 2) Keep the upper decks, widen them to 10 lanes, and convert the lower deck to HOV/Bus lanes with local exits, perhaps even connecting them with the proposed frontage roads for local access. Perhaps, the upper deck lanes can even be extended N to 183/290 while the frontage roads can serve as a "boulevard and freshened using the same Context Sensitive Solutions design methods proposed in the "cut and cap" proposal.

Just winging some suggestions around...

This is essentially what I have in mind above except I wasn't sure if it would allow for 10 lanes. Not sure if there would need to be an extension to 183 as there is just enough ROW to expand at grade one additional lane each direction.

[Revive 755]

I'm just waiting for some New Urbanist anti-freeway radical to intervene and call for simply ditching the double deck and everything else, converting I-35 to an 8-lane surface boulevard with continuous flow intersections replacing all the interchanges, and re-routing I-35 via SH 45 SE and SH 130 (or even I-10 E of San Antonio and SH 130 from Luling northward.

*ducking for cover* 

Nah, CFI's would still be too pedesterian unfriendly, too much of a barrier, and still favor cars too much 

[NE2]

CFIs are shit for peds. Quit trolling.

[Road Hog]

I've always found the decks to be confusing if you're not driving through. One deck (upper, I think) leads to downtown exits and the other deck leads to exits for UT. They're not well-signed at the split.

[ethanhopkin14]

This is great. One problem is the bridges are at incostistant hights to each other, especially at the southern split. I guess that is still ok, but it will make the egineering a bit more difficult. I have thought about this for years, but it just seams almost impossible.

[Anthony_JK]

CFIs are shit for peds. Quit trolling.

So, what would you do, then? Convert I-35 into an 8-lane boulevard with dual lefts at every major intersection? Who's trolling who??

[US81]

I've always found the decks to be confusing if you're not driving through. One deck (upper, I think) leads to downtown exits and the other deck leads to exits for UT. They're not well-signed at the split.

You are correct, that is how it's signed - but the roads reunite before downtown. Traffic is often backed-up, due to a lane drop, due to downtown, and sometimes the traffic slowing to climb up out of the river valley backs up into the downtown freeway itself.  That usually makes it easy to change lanes and access downtown from either deck.  The signage is unclear. I go through there from time to time and I definitely see lots of slowing and lane changes and even the rare stop-in-the-middle-of-the-freeway-while-I-figure-out-what-I-want-to-do obstruction. (Grrr!)

[Brandon]

CFIs are shit for peds. Quit trolling.

So, what would you do, then? Convert I-35 into an 8-lane boulevard with dual lefts at every major intersection? Who's trolling who??

AHHHHHHHHHHHHHH!!!!! 

That's just as bad for both traffic and pedestrians.  Use a Michigan Left setup. 

Anyway, what's done is done, and I-35 is there and is a freeway, and I-35 will remain a freeway for the foreseeable future.

[ethanhopkin14]

I-35 will never be moved from downtown. Something needed to be done yes, but expanding the lower deck is not going to happen. TxDOT cannot get the ROW to do it. That's why a tunnel is the best option, but just seems like a mess.