Double-decking freeways. Where would it make sense?

[OCGuy81]

I know that most cities really want to avoid a double decker highway.  They're absolute eye sores, but there's probably places where it might be the only option for future expansion.  What are some areas where the only option might be stacking? 

I feel the following areas would qualify.

* I-5 through Seattle.  Despite dismantling the eyesore that was the Alaskan Way viaduct, it looks like the only option to ever expand capacity on I-5, roughly from the I-90 interchange to the Northgate area, would be to double deck.

* I-94, the East-West Freeway in Milwaukee.  I know right past Miller Par...errrr...American Family Field, 94 has cemeteries on both sides, and I think if they needed to expand the freeway (which given traffic on it, may be needed) they'd have to stack the freeway.

*I-90/94 the Dan Ryan in Chicago.  I don't think there's any space for additional lanes here.

[roadman65]

I-4 near Disney instead of taking away ROW from the sides when they do the Beyond The Ultimate. 

[jeffandnicole]

Schuylkill Expressway

[Max Rockatansky]

The trouble with saying San Francisco or Seattle is that someone will inevitably bring up seismic risk.  Honolulu comes to mind with H-1, especially since H-4 was never constructed. 

[OCGuy81]

The trouble with saying San Francisco or Seattle is that someone will inevitably bring up seismic risk.  Honolulu comes to mind with H-1, especially since H-4 was never constructed. 

I don't think I'm familiar with H-4.  Was that meant to be a bypass?

[Max Rockatansky]

The trouble with saying San Francisco or Seattle is that someone will inevitably bring up seismic risk.  Honolulu comes to mind with H-1, especially since H-4 was never constructed. 

I don't think I'm familiar with H-4.  Was that meant to be a bypass?

Alternate through downtown:

https://www.gribblenation.org/2021/12/paper-highways-interstate-h-4-through.html?m=1

[NWI_Irish96]

*I-90/94 the Dan Ryan in Chicago.  I don't think there's any space for additional lanes here.

The Dan Ryan backs up because of the capacity of the freeways it feeds into, not because of its own capacity. Adding lanes, elevated or otherwise, wouldn't do much.

I-80/94 from IL 394 to I-65, however, could benefit from more lanes, and they'd have to be elevated.

[OCGuy81]

The trouble with saying San Francisco or Seattle is that someone will inevitably bring up seismic risk.  Honolulu comes to mind with H-1, especially since H-4 was never constructed. 

I don't think I'm familiar with H-4.  Was that meant to be a bypass?

Alternate through downtown:

https://www.gribblenation.org/2021/12/paper-highways-interstate-h-4-through.html?m=1

Oof, that would've been a mess had it been built.

[Max Rockatansky]

The trouble with saying San Francisco or Seattle is that someone will inevitably bring up seismic risk.  Honolulu comes to mind with H-1, especially since H-4 was never constructed. 

I don't think I'm familiar with H-4.  Was that meant to be a bypass?

Alternate through downtown:

https://www.gribblenation.org/2021/12/paper-highways-interstate-h-4-through.html?m=1

Oof, that would've been a mess had it been built.

More or less Hawaii 92 is the corridor that was ultimately constructed.  From Waikiki heading westbound Hawaii 92 tends to be faster than taking H-1.  The planners were definitely onto something with traffic patterns.

[ZLoth]

The Dallas North Tollway between I-635 at the North end and I-35E at the South end. It may be the most cost effective than trying to expand the highway via eminent domain since this tollway is hitting some of the most expensive neighborhoods in Dallas.

[paulthemapguy]

I-80/94 from IL 394 to I-65, however, could benefit from more lanes, and they'd have to be elevated.

Building the Illiana Expressway would have helped, but that never came to pass.

The one place I'm sure could have used elevated lanes would be the Eisenhower Expressway, I-290, east of I-294 into downtown. There's no lateral way to expand it.  Of course, a long viaduct is way, way more expensive than putting a highway on the ground, so take it with a grain of salt when I mention any 2-level highway's feasibility in the grand scheme of things.

[TheHighwayMan3561]

The trouble with saying San Francisco or Seattle is that someone will inevitably bring up seismic risk.  Honolulu comes to mind with H-1, especially since H-4 was never constructed. 

Double deckers are also eyesores if you put them in the wrong places.

[Max Rockatansky]

The trouble with saying San Francisco or Seattle is that someone will inevitably bring up seismic risk.  Honolulu comes to mind with H-1, especially since H-4 was never constructed. 

Double deckers are also eyesores if you put them in the wrong places.

Subjective opinion on my end, but downtown Seattle looks off now without the Viaduct.

[StogieGuy7]

I-80/94 from IL 394 to I-65, however, could benefit from more lanes, and they'd have to be elevated.

Building the Illiana Expressway would have helped, but that never came to pass.

The one place I'm sure could have used elevated lanes would be the Eisenhower Expressway, I-290, east of I-294 into downtown. There's no lateral way to expand it.  Of course, a long viaduct is way, way more expensive than putting a highway on the ground, so take it with a grain of salt when I mention any 2-level highway's feasibility in the grand scheme of things.

At least there are public transit options to avoid the Ike; the Borman, OTOH, is the only way to drive from the west shore of Lake Michigan to anywhere east of it. Elevating another 10 lanes above it would be an intriguing - though expensive - idea. Honestly, something will have to be done there. And, given that 80/94 runs through the outskirts of the apocalypse zone, who really cares if an elevated freeway is ugly. That whole region is an eyesore anyhow.

[tmoore952]

The trouble with saying San Francisco or Seattle is that someone will inevitably bring up seismic risk.  Honolulu comes to mind with H-1, especially since H-4 was never constructed.

The obvious (to me) seismic example is the Oakland double decker that was destroyed in the 1989 San Francisco earthquake (with crushed cars and fatalities), but I know part of the problem there had to do with the soil on which it was built, and there might have been issues with the construction itself as well. I have a Great Courses lecture on that engineering failure which I last viewed about a year ago.

But when I see the ages of some of the people posting, maybe that isn't so obvious.

[Bruce]

* I-5 through Seattle.  Despite dismantling the eyesore that was the Alaskan Way viaduct, it looks like the only option to ever expand capacity on I-5, roughly from the I-90 interchange to the Northgate area, would be to double deck.

I-5 is already double-decked from Madison Street to Mercer Street and across the Ship Canal Bridge, with the express lanes on the lower deck. Due to how the topology works, trying to add another deck to the other sections would be difficult and prohibitively expensive, plus the ramps would need to be steep or long.

The footprint is also used to its near maximum in many areas, so building columns for such a structure would require removing lanes for years at a time. For the new SR 520-to-express lane ramp under construction right now (and not scheduled to open until 2030), there's an express lane closed and several shaved lanes all around. Imagining this on a larger scale would really bring the city to its knees.

Subjective opinion on my end, but downtown Seattle looks off now without the Viaduct.

I have to disagree. I avoided the viaduct as much as I could when walking around the waterfront, so its absence has not felt out of place. It's so much quieter down on Alaskan Way, even with traffic still there.

[Max Rockatansky]

To clarify my position, I love industrial/brutalist highway aesthetic.  Perhaps that has something to do with me growing up in Detroit around where it is a common facade.  The Viaduct certainly had that feel and aesthetic in spades.  The Alaskan Way Tunnel certainly is nowhere nearly as interesting and definitely doesn't have the kick ass view of downtown the Viaduct.  All this urban renewal/modern aesthetic comes off to me as bland and samey.  At minimum I suppose that aesthetic isn't far away from Alaskan Way in the form of Pioneer Square.

[Ted$8roadFan]

Cross Bronx Expressway
Brooklyn Queens Expressway

I know it'll probably never happen, but still........

[Bruce]

To clarify my position, I love industrial/brutalist highway aesthetic.  Perhaps that has something to do with me growing up in Detroit around where it is a common facade.  The Viaduct certainly had that feel and aesthetic in spades.  The Alaskan Way Tunnel certainly is nowhere nearly as interesting and definitely doesn't have the kick ass view of downtown the Viaduct.  All this urban renewal/modern aesthetic comes off to me as bland and samey.  At minimum I suppose that aesthetic isn't far away from Alaskan Way in the form of Pioneer Square.

There's still plenty of industrial-looking places around town, but it really had no place being on so much of the waterfront (basically our front door) and next to historic Pioneer Square. For example, there's still the steam plant off Union Street or the entire port for waterfront industrial vibes. Once the promenade is finished, it'll look far better and bring some new life to the transition zone in downtown that is pockmarked with multi-story garages and random nonsense uses.

The tunnel was a costly mistake, given how little it actually helps with mobility. It should have been pointed northwest towards Interbay to redirect freight, if built at all.

[Max Rockatansky]

To clarify my position, I love industrial/brutalist highway aesthetic.  Perhaps that has something to do with me growing up in Detroit around where it is a common facade.  The Viaduct certainly had that feel and aesthetic in spades.  The Alaskan Way Tunnel certainly is nowhere nearly as interesting and definitely doesn't have the kick ass view of downtown the Viaduct.  All this urban renewal/modern aesthetic comes off to me as bland and samey.  At minimum I suppose that aesthetic isn't far away from Alaskan Way in the form of Pioneer Square.

There's still plenty of industrial-looking places around town, but it really had no place being on so much of the waterfront (basically our front door) and next to historic Pioneer Square. For example, there's still the steam plant off Union Street or the entire port for waterfront industrial vibes. Once the promenade is finished, it'll look far better and bring some new life to the transition zone in downtown that is pockmarked with multi-story garages and random nonsense uses.

The tunnel was a costly mistake, given how little it actually helps with mobility. It should have been pointed northwest towards Interbay to redirect freight, if built at all.

The problem I foresee is the waterfront isn't going to fit the rest of the motif.  No matter how retro someone tries to make that waterfront property look it is going to come off as modernist.  Every time I pass through the area for work it just looks all wrong/odd/off along Alaskan Way.  But that's the outside observer opinion, I'm certainly not a local and I know the Viaduct wasn't popular for many reasons.

We are in agreement on the Tunnel.  The Tunnel is definitely not as useful as the Viaduct was for me in my travels.  I mostly stick to I-405 or try to grab a ferry somewhere nowadays on work trips to bypass downtown Seattle.

[pderocco]

I don't object to double-decked highways, as long as they're concrete, and not defacing a waterfront. I've had enough of 1950s steel girders painted green. L.A. has a stretch of I-110 that has elevated express lanes, which are rather spectacular.

The Seattle waterfront always had the potential of being one of the nicest spots in the city, and now that's coming to fruition. A double-decked I-5 inland would be a good trade.

Maybe double-decking US-26 coming into Portland from the west would be useful, since it's in a narrow canyon. Can you imagine a third tunnel through the Southwest Hills above the existing tunnels? That would be an engineering novelty.

[Henry]

Something that's actually being proposed in real life:

I-75/I-85 Downtown Connector in Atlanta

*I-90/94 the Dan Ryan in Chicago.  I don't think there's any space for additional lanes here.

At this point, you'd also have to include the Kennedy Expressway in this.

[Duke87]

Subjective opinion on my end, but downtown Seattle looks off now without the Viaduct.

I have to disagree. I avoided the viaduct as much as I could when walking around the waterfront, so its absence has not felt out of place. It's so much quieter down on Alaskan Way, even with traffic still there.

I mean, this stuff is so much in the eye of the beholder. Personally I think the Embarcadero Freeway was a beautiful work of art and wish I'd had the chance to experience it while it was still standing. Being able to experience the Alaskan Way viaduct while it was still standing was a consolation prize at least.

Regardless, I love intricate infrastructure shoehorned into places like that. Sure, a landscaped boulevard is more tourist-friendly, but it just seems so sanitized and boring in comparison. Like, there are tons of places I can stand along a city waterfront with the sky overhead, it's a dime a dozen experience made for basic normal people. Standing along a city waterfront with traffic roaring by overhead at 60 mph? Now that's actually something special.

Unpopular opinion, I know. 🤷

[Max Rockatansky]

In a historic context Alaskan Way has almost always had shoehorned infrastructure.  It makes me wonder how people in modern times would react to how things were when it was the planked Railroad Avenue.  The whole concept of a wooden trestle roadway with railroad tracks running alongside seems intriguing to envision:

https://www.historylink.org/File/9925

https://pauldorpat.com/2019/02/23/seattle-now-then-railroad-avenue-1920/

[Bruce]

In a historic context Alaskan Way has almost always had shoehorned infrastructure.  It makes me wonder how people in modern times would react to how things were when it was the planked Railroad Avenue.  The whole concept of a wooden trestle roadway with railroad tracks running alongside seems intriguing to envision:

https://www.historylink.org/File/9925

https://pauldorpat.com/2019/02/23/seattle-now-then-railroad-avenue-1920/

Being a working waterfront, Alaskan Way/Railroad Avenue was never meant to be pretty. Now that most of that industry has been consolidated and moved to different quarters (SODO, Tacoma, or even overseas), the city wants to seize on the opportunity to create a pleasant linear park; it's sorely needed given the lack of parkspace in downtown itself due to oversights by the town founders and an acceptance in the 20th century that random corporate plazas were suitable replacements (which they are not). While it may seem generic and boring, it appeals to most people who live here and most who visit.

There were a lot of wooden trestle roads that may or may not have carried trains built around the Northwest. Astoria still has one for their revived trolley (which has to share ROW with both cars and pedestrians at various points).