Flyovers replaced by loops (or something else low capacity)

[jakeroot]

This was originally to be a post in the Washington [state] thread, but I made it into its own thread because I find it so unusual.

While doing some research on these strange mile-markers in Washington State (thank you Bruce for the link), I started to look more into the Swamp Creek Interchange, which is the junction of I-405, I-5, and WA-525 in Lynnwood.

Back when it was originally constructed in the 1960s, it was a three-way fully-directional Y-interchange, with a flyover between northbound 405 and southbound 5. However, when the 525 was extended south to meet the Swamp Creek interchange in the early 1980s, the northbound to southbound flyover was removed and replaced with a loop in the northern (northwestern?) corner of the interchange.

From what I can tell, the flyover was single lane, the same as the loop ramp that replaced it. I'm guessing the flyover didn't have much traffic, since traffic using it was already going north on the 405 for quite a while by this point, and largely was proceeding north on 5, rather than south. When the 525 was built to the junction in the early/mid 1980s, that was expected to become a major movement (and still very much is), so the interchange was reconstructed with a major northbound to northbound underpass, and the southbound to southbound ramp was also rebuilt to be on the right side of the freeways, rather than the inside, and runs adjacent to the other underpass to this day.

Here's some before and after images:



So, how often have you seen something like this happen? Most of the time, when interchanges are rebuilt to become four-ways from three-ways, the original interchange has already been built to accommodate the extension. This was not the case, despite the original interchange being built less than twenty years before it was reconstructed.

[ErmineNotyours]

And the loop is largely elevated, negating much of the cost savings of making it a loop.

I wonder if something like that might have happened on the other end of Washington 405.  Going southbound there is a weird section where the lanes shift left relative to the concrete panels, and the right-most panel lane ends.  I wonder if the interchange was once designed for the right lane to lead to a flyover to south I-5, but then they decided to put in a loop instead.

[jakeroot]

And the loop is largely elevated, negating much of the cost savings of making it a loop.

I wonder if something like that might have happened on the other end of Washington 405.  Going southbound there is a weird section where the lanes shift left relative to the concrete panels, and the right-most panel lane ends.  I wonder if the interchange was once designed for the right lane to lead to a flyover to south I-5, but then they decided to put in a loop instead.

Great observation. Though there are plentiful historic aerial photographs, I see no evidence at any point of there being a flyover planned for that movement. Funny thing is that, if a flyover were needed at that interchange (and it's amazing that it somehow doesn't have anything more than a bunch of terrible inside-to-inside underpasses), it would absolutely be that movement. At this point, as a carpooler, I've taken to using 167 and that new HOV flyover instead of going all the way to I-5, since that whole interchange is just so awful.

[STLmapboy]

The Chestnut/20th intersection off Highway 40 in Downtown St Louis will be replaced by a diamond to 22nd.

[ilpt4u]

The Chestnut/20th intersection off Highway 40 in Downtown St Louis will be replaced by a diamond to 22nd.

There is even a thread about it in the Central States board: https://www.aaroads.com/forum/index.php?topic=25883.0

The land from the cancelled MO 755 Freeway that the old interchange was designed for is being developed into an MLS soccer stadium

[Elm]

I didn't have high expectations for finding an example in Colorado, but the I-25/US 36/I-270/I-76 interchange complex (a distinctively complicated interchange for the state) delivered something like it, specifically in what's now the interchange of I-25, US 36, and I-270 (Google Maps). For twenty-some years, there was a flyover from present-day US 36 eastbound to I-25 northbound, and the movement is now handled by a loop.

That interchange has gone through several variations as the area highways developed (and produced the broader "˜interchange complex'). It started out as part of a mostly at-grade "Valley Highway extension"  from now-I-25 at 70th Ave to the Boulder Turnpike at Federal Blvd. At that point, there was no southeast-to-north movement (1958 topo; later article with map).

When Broadway was grade-separated, slip ramps were added from the existing interchange to complete a diamond there (1964 aerial). The southeast-to-north flyover came sometime after that, probably in the early 70s, but I didn't find any text references to it (1973 topo). A lane was also added to allow traffic from I-76 (then I-80S) to continue onto northbound I-25. (Incidentally, you can see a nasty little weave there to get from I-80S to US 36.)

In the 90s and 2000s, there were a bunch of projects in the area that affected the interchange, including extensions of I-270 and I-76 and bus (later HOT) lanes between I-25 and US 36. The switch from flyover to loop seems most related to making room for the eastbound through movement from US 36 to I-270 (1994 view), and a left exit from southbound I-25 to eastbound I-270 also now occupies the flyover's "˜level' of the interchange.

As far as traffic volumes go, I don't know but would believe that the eastbound US 36 to northbound I-25 movement is relatively less used than others. (The opposite southbound I-25 to westbound US 36 goes through a signal at the Broadway interchange.) Depending on your trip, it might be more direct to take a surface road between the US 36 area and I-25 instead of going south through the interchange to stay on freeways.

[ErmineNotyours]

SR 16 & Sprague Ave, Tacoma:

Before:
Full interchange

After:
Signalized T-intersection

[catch22]

Here's one that may fit.  It's the US-12/BUS US-12 split in Ypsilanti Township, MI.  MDOT decided to do this rather than rebuild the bridge.

Before:



After:

[jakeroot]

The Chestnut/20th intersection off Highway 40 in Downtown St Louis will be replaced by a diamond to 22nd.

There is even a thread about it in the Central States board: https://www.aaroads.com/forum/index.php?topic=25883.0

The land from the cancelled MO 755 Freeway that the old interchange was designed for is being developed into an MLS soccer stadium

That's pretty cool to see. I lived in STL for a couple years (on and off) and that interchange always struck me as something designed for something greater. It's replacement with something lower capacity seems more than warranted, as it was always very lightly travelled.

[jakeroot]

SR 16 & Sprague Ave, Tacoma:

Before:
Full interchange

After:
Signalized T-intersection

Right in my backyard and I totally forgot about this brilliant example. Weirdly, I think it works better now, since there are two entrance ramps depending on the direction you want to go.

I think I would have thought about it eventually, but I actually changed the thread from being exclusively about "flyovers replaced by loops" to "flyovers replaced by literally anything lower capacity".

[renegade]

Here's one that may fit.  It's the US-12/BUS US-12 split in Ypsilanti Township, MI.  MDOT decided to do this rather than rebuild the bridge.

Before:



After:

My previous home is just out of frame in the upper left corner of both pictures.

[jakeroot]

I didn't have high expectations for finding an example in Colorado, but the I-25/US 36/I-270/I-76 interchange complex (a distinctively complicated interchange for the state) delivered something like it, specifically in what's now the interchange of I-25, US 36, and I-270 (Google Maps). For twenty-some years, there was a flyover from present-day US 36 eastbound to I-25 northbound, and the movement is now handled by a loop.

That interchange has gone through several variations as the area highways developed (and produced the broader "˜interchange complex'). It started out as part of a mostly at-grade "Valley Highway extension"  from now-I-25 at 70th Ave to the Boulder Turnpike at Federal Blvd. At that point, there was no southeast-to-north movement (1958 topo; later article with map).

When Broadway was grade-separated, slip ramps were added from the existing interchange to complete a diamond there (1964 aerial). The southeast-to-north flyover came sometime after that, probably in the early 70s, but I didn't find any text references to it (1973 topo). A lane was also added to allow traffic from I-76 (then I-80S) to continue onto northbound I-25. (Incidentally, you can see a nasty little weave there to get from I-80S to US 36.)

In the 90s and 2000s, there were a bunch of projects in the area that affected the interchange, including extensions of I-270 and I-76 and bus (later HOT) lanes between I-25 and US 36. The switch from flyover to loop seems most related to making room for the eastbound through movement from US 36 to I-270 (1994 view), and a left exit from southbound I-25 to eastbound I-270 also now occupies the flyover's "˜level' of the interchange.

As far as traffic volumes go, I don't know but would believe that the eastbound US 36 to northbound I-25 movement is relatively less used than others. (The opposite southbound I-25 to westbound US 36 goes through a signal at the Broadway interchange.) Depending on your trip, it might be more direct to take a surface road between the US 36 area and I-25 instead of going south through the interchange to stay on freeways.

That's a great example! Exactly what I had in mind when I thought of this thread. It even parallels my example by having the interchange modified from three directions to four directions. Very well found.

The way it's setup now seems more than adequate, especially given the diameter of the east to north loop that was built instead, although I think if done today, that loop might not be ideal given how much redundant land there is within the loop in what is otherwise a relatively urban area (example of an urban loop designed to accommodate businesses). Then again, fitting in another flyover would have been damn tough without a lot more money. Plus, who knows how busy it is since it's at the "southern" end of the US-36 Freeway, which I know starts way up north-northwest in Boulder (and I doubt many are going all the way south to this point, only to go north on I-25 -- although I understand that plenty of traffic originates south of that point).

[jakeroot]

Here's one that may fit.  It's the US-12/BUS US-12 split in Ypsilanti Township, MI.  MDOT decided to do this rather than rebuild the bridge.

Before:



After:

As originally envisioned? No, it would not have fit, since I wanted examples of flyovers replaced by loops.

But, since that is obviously quite unusual, and I wanted more than three replies: yes, this definitely fits, since there can be no doubt the movement now has less capacity than it did before. Classic example, I suspect, of changing traffic conditions no longer warranting such a high capacity ramp. This may have been the case in my original example, and is almost certainly the case of the example in Denver (directly above) as well.

[TEG24601]

I saw the Swamp Creek interchange when I first discovered Historic Aerials.  I was amazed that such an interchange would have been changed as it was.  I wonder how a flyover would work with the braiding that was done to interface with 196th St., or why there is no SB-525 to NB-5 or SB-5 to NB-525 movements (which are need).  Of course WSDOT has preplanned a lot of things for when things reach capacity at that interchange, so we may see the return of some flyovers in the future.


As for examples, the only thing that seems close that I can quickly recall is I-94 and US 24/Telegraph Rd., being converted from an sweet interlocking left loop interchange into a SPUI.


https://www.historicaerials.com/location/42.2640028799395/-83.26819397196591/2002/16 (Old)
https://www.historicaerials.com/location/42.26471746830239/-83.26849449713622/2010/16 (New)

[seicer]

And the loop is largely elevated, negating much of the cost savings of making it a loop.

I wonder if something like that might have happened on the other end of Washington 405.  Going southbound there is a weird section where the lanes shift left relative to the concrete panels, and the right-most panel lane ends.  I wonder if the interchange was once designed for the right lane to lead to a flyover to south I-5, but then they decided to put in a loop instead.

I was thinking that it could have been the drop lane for the south I-5 ramp if the bridge was widened.

[EpicRoadways]

The ramp from US-8 WB to I-35 SB in Forest Lake, MN was a flyover until last year; it was replaced with a loop ramp last year due to interchange spacing concerns with the next interchange to the south. Satellite shows the project nearly complete, while Streetview shows the project in earlier stages of construction with the former flyover ramp still intact. 

[STLmapboy]

The ramp from US-8 WB to I-35 SB in Forest Lake, MN was a flyover until last year; it was replaced with a loop ramp last year due to interchange spacing concerns with the next interchange to the south. Satellite shows the project nearly complete, while Streetview shows the project in earlier stages of construction with the former flyover ramp still intact.

I drove through there in July, it was complete.

[BrianP]

The Steve Whalen Blvd flyover on US 35 was rightfully removed in Dayton OH because the route it was suppose to become was cancelled long ago.  The flyover went from northbound SW Blvd to US 35 westbound.
https://www.google.com/maps/@39.7546635,-84.1587866,527m/data=!3m1!1e3

[jakeroot]

I saw the Swamp Creek interchange when I first discovered Historic Aerials.  I was amazed that such an interchange would have been changed as it was.  I wonder how a flyover would work with the braiding that was done to interface with 196th St., or why there is no SB-525 to NB-5 or SB-5 to NB-525 movements (which are need).  Of course WSDOT has preplanned a lot of things for when things reach capacity at that interchange, so we may see the return of some flyovers in the future.

I always wondered about that missing movement. In my head, I've always told myself that there was no way enough traffic was going all the way south on 525 to need to go north on 5, and vice versa. But then, it might be easier to justify not having those ramps if they installed a new interchange at 164th. It could incorporate a bus stop with the Swamp Creek Park and Ride being right there. Community Transit operates several routes at that stop already, and a couple of routes do use 525. But who knows if that transfer was needed at all, or that stop anyways.

[jakeroot]

The ramp from US-8 WB to I-35 SB in Forest Lake, MN was a flyover until last year; it was replaced with a loop ramp last year due to interchange spacing concerns with the next interchange to the south. Satellite shows the project nearly complete, while Streetview shows the project in earlier stages of construction with the former flyover ramp still intact.

I drove through there in July, it was complete.

That's a very interesting example! It almost totally resembles an interchange that is only partially complete. Had you not explained the reasoning for the reconstruction (close proximity to another ramp), I would have assumed the interchange was realigned to support a western extension. I'm guessing that's not the plan?

I think the typical plan for this type of situation would be to installed collector/distributor lanes or another carriageway to allow cars to change lanes without interfering with through traffic. Easiest way would have been to have the off-ramp to Broadway start before the flyover came in, come around the outside of it, and then have the flyover split to allow traffic to exit towards Broadway or continue onto I-35 SB. Same approach as this interchange in Surrey, BC.

[jakeroot]

The Steve Whalen Blvd flyover on US 35 was rightfully removed in Dayton OH because the route it was suppose to become was cancelled long ago.  The flyover went from northbound SW Blvd to US 35 westbound.
https://www.google.com/maps/@39.7546635,-84.1587866,527m/data=!3m1!1e3

That was a mighty impressive interchange as originally built. Rare to see an interchange reduced in capacity by that much without there having been an ulterior motive in the original design, such as a freeway (as was the case here).

I think the lack of any protected phase for the left turn from northbound Steve Whalen Blvd to westbound US-35 is fairly telling as to how busy the flyover wasn't.

[ari-s-drives]

The SR 77 stub (42nd Avenue) in Oakland apparently used to have a full freeway interchange at I-880, but was refitted to a diamond in 2011.

2002:


2016:

[BrianP]

The Steve Whalen Blvd flyover on US 35 was rightfully removed in Dayton OH because the route it was suppose to become was cancelled long ago.  The flyover went from northbound SW Blvd to US 35 westbound.
https://www.google.com/maps/@39.7546635,-84.1587866,527m/data=!3m1!1e3

That was a mighty impressive interchange as originally built. Rare to see an interchange reduced in capacity by that much without there having been an ulterior motive in the original design, such as a freeway (as was the case here).

I think the lack of any protected phase for the left turn from northbound Steve Whalen Blvd to westbound US-35 is fairly telling as to how busy the flyover wasn't.

Thanks to Kurumi's post which led to a post about Dayton's cancelled expressways.  Steve Whalen Blvd was to be part of the Southeast Expressway and an early version of I-675.  I had heard of the latter but not the former.  The Southeast Expressway seems to have evolved into Wilmington Ave. 

[Gnutella]

In Pennsylvania, the I-70/I-79 interchange with U.S. 19 (Murtland Avenue) was downgraded from a cloverleaf to a diverging diamond.

[johndoe]

I cheated and used the map of alternative intersections (http://go.ncsu.edu/aii), figuring that some DDI probably replaced flyovers.  Didn't find as many as I thought I would:

Kansas: https://www.google.com/maps/d/view?mid=1MMZKi0RdQqjZjtBxmSTznUVnurY&ll=39.10857065868863%2C-94.74183228858857&z=16

Missouri: https://www.google.com/maps/d/view?mid=1MMZKi0RdQqjZjtBxmSTznUVnurY&ll=39.15960056366447%2C-94.50039508518923&z=16