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[Tom958]

I-10 at AL 163 Dauphin Island Parkway in Mobile. It's in Alabama, but it's unusually elaborate for a service interchange in that state, and most of the bridges are cast-in-place concrete box beams, which are rare in Alabama. It looks like Louisiana designed the layout and Mississippi designed the bridges.

Obviously, AL 163 was meant to serve as the major route to Dauphin Island- - hence the elaborate interchange. However, in 1968, only a few years after the interchange's completion in 1965, Hurricane Camille destroyed that route's bridge over the Deer River. Rather than rebuilding the AL 163 bridge, AL 193 was made the major route to Dauphin Island. It crosses the Deer River upstream of the dock complexes and thus requires only a modest bridge.

[froggie]

^ I figured the design had something to do with the immediately-adjacent-to-10 CSX tracks, and for some reason they didn't curve slightly north like they did at Michigan Ave.

[Dirt Roads]

I-10 at AL 163 Dauphin Island Parkway in Mobile. It's in Alabama, but it's unusually elaborate for a service interchange in that state, and most of the bridges are cast-in-place concrete box beams, which are rare in Alabama. It looks like Louisiana designed the layout and Mississippi designed the bridges.

Obviously, AL 163 was meant to serve as the major route to Dauphin Island- - hence the elaborate interchange. However, in 1968, only a few years after the interchange's completion in 1965, Hurricane Camille destroyed that route's bridge over the Deer River. Rather than rebuilding the AL 163 bridge, AL 193 was made the major route to Dauphin Island. It crosses the Deer River upstream of the dock complexes and thus requires only a modest bridge.

^ I figured the design had something to do with the immediately-adjacent-to-10 CSX tracks, and for some reason they didn't curve slightly north like they did at Michigan Ave.

Yes, CSX has some pretty tough requirements for overpasses, mostly related to clearance and crashworthiness (in the case of derailments).

[Tom958]

^ I figured the design had something to do with the immediately-adjacent-to-10 CSX tracks, and for some reason they didn't curve slightly north like they did at Michigan Ave.

Let's think this out: why didn't they build a diamond, like the one at Michigan Avenue? The obvious answer is that they wanted a high-volume semidirect ramp for the westbound 10 to southbound 163 movement. It's not obvious to me, though, why they couldn't have built the southwest quadrant of the interchange as it is and the rest of the interchange as a diamond.

It appears to me that the design was driven by the desire for that semidirect ramp from southbound 163 to eastbound 10, which required the mainline 163 bridge to be a great deal higher and therefore longer than it otherwise would've needed to be. They could've gone with a loop ramp for that movement instead, especially since the layout of the westbound-to-southbound ramp created a nice, big space for it, but it would've required a lot of bridgework, too, and the ramp would've been inferior. That said, going with a semidirect ramp instead of a loop also created a need for something other than an at-grade left turn from northbound 163 to westbound 10. Cha-ching.

So, why was that movement deemed so important? The only thing I can think of is that the planners anticipated a lot of traffic using McVey Drive to access I-10 there, enough to overload a signalized left turn movement. Anyway, once the decision was made to elevate so much of the interchange, there was no point in curving the mainline away from the railroad.

Or maybe they just wanted to build a cool interchange there.   

[codyg1985]

You may argue, but to me the idiots who thought this would work were CRAZY:

https://www.google.com/maps/@35.1246454,-90.0692547,646m/data=!3m1!1e3

There was never a chance that having one lane in each direction for I55 (plus the one lane cloverleaf loop) was ever going to be anything but a cluster.

TDOT was going to embark on a project to revamp that interchange by routing I-55 onto a sweeping curved overpass on the southwest quadrant of the interchange, and having all other movements culminate at a roundabout. Unfortunately, there was a lot of public outcry when it was announced that the I-55 Mississippi River bridge would have to be closed for nine months in order to build the interchange, As a result, no work has taken place.

[codyg1985]

Speaking of I-77, how about the wrong-way interchange at I-85?

It's basically the DDI concept translated to a "system" format with over/underpasses replacing the signals at the directional crossings.  The old I-95/695 interchange NE of Baltimore was quite similar. 

The main interchange in Downtown Birmingham on I-65 at I-20/59 is basically the same as the former one in Baltimore.  It looks like the recent 20/59 reconstruction added some new auxiliary ramps/flyovers to serve other nearby streets, but the original bones of the interstate-to-interstate movements still remain.

I believe the main interchange with I-20/59 and I-65 is even more complex now because all of the ramps from I-65 and I-20/59 to downtown are mixed in with the main movements with the interchange. Some of those new exits are left exits as well. The new setup still doesn't address the issues of the curves both within and approaching the interchange on both roads being tough enough that sometimes trucks take them too fast. Combine that with having to be on the left to exit or you enter the freeway from the left and jockeying with other vehicles, and you have more truck accidents that shut the freeway down for hours.

The current setup is nice in that it takes the downtown exits away from the main I-20/59 viaduct through downtown, but I believe the entire I-20/59/65 interchange needs to be rethought.

[planxtymcgillicuddy]

This weird-looking figure eight interchange on the Bluegrass Parkway south of Bloomfield, Kentucky. Another one of these existed on the Cumberland at Russell Springs until about 5 years ago