I-10 Upper and Lower Levels in San Antonio

[roadman65]

I was there back in 97 and was most impressed with the upper and lower levels of I-10 west of I-35 and the one on I-35 between I-10 and I-37. The piers that hold the upper freeway above the lower freeway are awesome!

I was wondering if the lower road is supposed to be the Express Lanes like NJ has on its urban area interstates, but with the inner roadway being express in this case.  I see that not all interchanges are between both grades and the lower level is only at two lanes while its upper counterpart has three.  There is one where you have to be on top to access the exit while the ground floor passes under it with no ramps.  So am I to assume this is Texas way of saying Express and Local or was it a means to widen the road without taking too much land as the two grades are cantilevered over each other and the lower level was constructed first as it has the older bridges.

[kphoger]

I know that, driving northbound on I-35, signs direct I-35 traffic onto either the lower or upper decks.  But, really, you can take either one, you just have to do some lane changing when they come back together again.  I've actually only driven on it once, as I always prefer to bypass San Antonio on I-410; the one time I did was because we were following our other vehicle, and the driver didn't know to use 410.

In Austin, I almost always take the upper deck.  I've taken the lower one once on a Sunday, just to see what it was like.

[J N Winkler]

Actually, San Antonio has multiple two split-level sections.  By ascending order of IH 35 mileage, two of them they are as follows:

http://maps.google.com/maps?q=San+Antonio,+TX&ie=UTF8&hq=&hnear=San+Antonio,+Bexar,+Texas&ll=29.410979,-98.507538&spn=0.002351,0.004823&t=m&z=18&vpsrc=6

http://maps.google.com/maps?q=San+Antonio,+TX&ie=UTF8&hq=&hnear=San+Antonio,+Bexar,+Texas&ll=29.437467,-98.490431&spn=0.00235,0.004823&t=m&z=18&vpsrc=6

These segments are divided by a wye interchange between IH 35 and IH 10 which is the northern end of an overlap between the two Interstates.

The signing leading into the southern split-level section on IH 35 northbound is actually rather confusing, at least when seen as a succession of sign elevation sheets in a construction plans set (TxDOT CCSJ 0915-00-122--the most recent sign replacement--in this case).  It says that the upper level is for IH 35 and US 87 southbound, while the lower level is for IH 35 northbound.  This message is really for the benefit of IH 10 eastbound traffic but as this length of road also carries an IH 35 overlap in the northbound direction, this signing fails to reassure drivers wishing to follow IH 35 northbound that "straight ahead" is the correct direction.  (Looking at both segments in Google Earth, I also don't see a turnaround point where traffic going northbound on this segment, on either level, gets onto IH 35 southbound.)

[NE2]

It says that the upper level is for IH 35 and US 87 southbound, while the lower level is for IH 35 northbound.

Someone must have fucked up the plans. The upper level is for I-10 west and US 87 north: http://maps.google.com/maps?hl=en&ll=29.409105,-98.508879&spn=0.004262,0.008256&gl=us&t=m&z=18&layer=c&cbll=29.408924,-98.508946&panoid=u5Wvt82kPyHi0r5i4e5qcQ&cbp=12,12.91,,0,-1.64

[J N Winkler]

It says that the upper level is for IH 35 and US 87 southbound, while the lower level is for IH 35 northbound.

Someone must have fucked up the plans. The upper level is for I-10 west and US 87 north: http://maps.google.com/maps?hl=en&ll=29.409105,-98.508879&spn=0.004262,0.008256&gl=us&t=m&z=18&layer=c&cbll=29.408924,-98.508946&panoid=u5Wvt82kPyHi0r5i4e5qcQ&cbp=12,12.91,,0,-1.64

Actually, it seems I misinterpreted the plans and am therefore the one that fucked up.  It turns out that there is a third split-level segment, on IH 10 northwest of the IH 10/IH 35 commons:

http://maps.google.com/maps?hl=en&gl=us&t=m&ie=UTF8&ll=29.439513,-98.506444&spn=0.004737,0.009645&z=17&vpsrc=6

In context the signing (which is for IH 10 eastbound around mileposts 568-570, not IH 35 northbound as I had originally thought) makes sense since the choice between the two directions of IH 35 there does not entail a 180° turnaround.

This is what I get for looking at the sign panel and sign elevation sheets without having the sign layouts handy (they are long since filed--this was a 2006 contract).

I have decided to edit my post upthread accordingly.

[roadman65]

I checked out all your links and one thing that remains is not all exits are accessed by both levels.  There are some that you must use the upper level, both on I-10 and I-35 that there is no accessibility from the lower levels.  Sure, both are signed as I-10, I-35, US 87 etc. but one has to be and express  that being the lower road (taken the two lane below grade lower level missing some  exits that the other one has and it being two laned) while the top level is the local (having more ramps exiting and entering it plus being three laned). 

[InterstateNG]

My best guess in deciphering the drivel you've written in both posts in this thread is that you think the split levels are some sort of local/express set up.  They aren't, it's just a way to increase capacity in an area where the right-of-way is extremely limited and to get traffic queued up well before the 35/10 junctions.

[kphoger]

Similarly, in Austin certain exits are accessed via the lower level and others via the upper level.

[texaskdog]

Similarly, in Austin certain exits are accessed via the lower level and others via the upper level.

Actually once you take the upper deck you can't exit until the end when it comes back down.  But the whole stretch is only 2 miles long.  I always fear it as if there is an accident, you're just plain stuck.

[kphoger]

Similarly, in Austin certain exits are accessed via the lower level and others via the upper level.

Actually once you take the upper deck you can't exit until the end when it comes back down.  But the whole stretch is only 2 miles long.  I always fear it as if there is an accident, you're just plain stuck.

While it is technically true that all southbound exits can be accessed via the lower level, 15th Street is only accessible via frontage road, including a stoplight at MLK Blvd–whereas the upper level has a direct ramp.  I believe there is no such difference northbound.

[texaskdog]

Similarly, in Austin certain exits are accessed via the lower level and others via the upper level.

Actually once you take the upper deck you can't exit until the end when it comes back down.  But the whole stretch is only 2 miles long.  I always fear it as if there is an accident, you're just plain stuck.

While it is technically true that all southbound exits can be accessed via the lower level, 15th Street is only accessible via frontage road, including a stoplight at MLK Blvd—whereas the upper level has a direct ramp.  I believe there is no such difference northbound.

That's true.  Northbound the upper deck is handy heading off MLK from the baseball & softball stadium, you can jump right on, not sure if you can access lower deck from there unless you stay on the frontage road.