Flyovers replaced by loops (or something else low capacity)

[tdindy88]

I immeditedly thought of the interchange between Interstate 465 and Sam Jones Expressway on the west side of Indianapolis. The previous interchange had three loops and a flyover ramp for southbound the eastbound traffic while the new interchange is a simple diamond. Since the Indianapolis International Airport terminal moved from near this interchange to the new midfield terminal back in 2008 the down-scaling of this interchange was appropriate. But plenty of traffic still uses this interchange especially in the southbound to eastbound movement which now requires stopping at a traffic light. It's no accident that this is one of the few intersections with three left turn lanes in Indianapolis.


New interchange on the left, old one on the right.

[Hot Rod Hootenanny]

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. 

Some years back, I had found a blog that had maps of the various proposed expressways for Dayton that were never built...
(Link to the AAroads post, which will have the link to the blog) https://www.aaroads.com/forum/index.php?topic=6879.0

[TheHighwayMan3561]

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.

Traffic volumes don't support that elaborate of a setup. 35 goes from 4 to 6 lanes at US 8, and I believe most of that traffic coming off 8 stays on I-35, so there's not a problem with weaving or crunches of vehicles trying to get off at Broadway.

[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.

Traffic volumes don't support that elaborate of a setup. 35 goes from 4 to 6 lanes at US 8, and I believe most of that traffic coming off 8 stays on I-35, so there's not a problem with weaving or crunches of vehicles trying to get off at Broadway.

But EpicRoadways just said that it was rebuilt due to interchange spacing concerns. These concerns generally arise when there is too much or too often conflicts between entering and exiting traffic. This would not be a problem if the exit to Broadway is light at best.

If weaving was a concern, they literally could have kept the flyover and built a new ramp around the existing flyover to exit at Broadway. There is no way that would have been more expensive than this huge loop thing they built, which looks more like an unfinished trumpet than something intentional.

[jakeroot]

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:

That was a pretty tight three-way interchange. Something tells me the new diamond may have similar throughput capabilities

[jakeroot]

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

I'm more looking for examples where flyovers or something close to it were replaced with loops or something else, not necessarily loops to something even lower capacity.

Still, I appreciate the input. Definitely saddens me to see something like that, when there would have been many other options with all those existing loops.

[jakeroot]

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

Both in the same metro area. Interesting. That second one is mighty impressive ... it doesn't even technically exist on Google Maps yet!

[jakeroot]

I immeditedly thought of the interchange between Interstate 465 and Sam Jones Expressway on the west side of Indianapolis. The previous interchange had three loops and a flyover ramp for southbound the eastbound traffic while the new interchange is a simple diamond. Since the Indianapolis International Airport terminal moved from near this interchange to the new midfield terminal back in 2008 the down-scaling of this interchange was appropriate. But plenty of traffic still uses this interchange especially in the southbound to eastbound movement which now requires stopping at a traffic light. It's no accident that this is one of the few intersections with three left turn lanes in Indianapolis.


New interchange on the left, old one on the right.

I remember reading about that interchange. This seems to be one of the few that truly doesn't make any sense. Maybe it's not the most major interchange anymore, but it's hard to believe that replacing that huge grade-separated interchange with a diamond will help anyone, really. It doesn't even have any sidewalks. So much for a more urban interchange!

[johndoe]

Yeah that Indy one is pretty interesting.  I could see them wanting to save bridge costs but the new diamond they installed is pretty beefy!  At first I wondered if the flyover had to go because flight paths, but that doesn't seem right.  Historic Aerials shows it open for 50 years, I'm impressed that was built so long ago.  Wonder if parclo A6 might have been a good fit.

[froggie]

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.

Traffic volumes don't support that elaborate of a setup. 35 goes from 4 to 6 lanes at US 8, and I believe most of that traffic coming off 8 stays on I-35, so there's not a problem with weaving or crunches of vehicles trying to get off at Broadway.

But EpicRoadways just said that it was rebuilt due to interchange spacing concerns. These concerns generally arise when there is too much or too often conflicts between entering and exiting traffic. This would not be a problem if the exit to Broadway is light at best.

If weaving was a concern, they literally could have kept the flyover and built a new ramp around the existing flyover to exit at Broadway. There is no way that would have been more expensive than this huge loop thing they built, which looks more like an unfinished trumpet than something intentional.

The driving need for the project was the need to replace the WB 8 bridge over 35.  MnDOT decided they could kill two birds with one stone by realigning the ramp to provide more space in between the ramps.  The weaving problem wasn't so much the traffic volume as it was the very short spacing...barely 800ft under the old configuration.

[Revive 755]

I immeditedly thought of the interchange between Interstate 465 and Sam Jones Expressway on the west side of Indianapolis. The previous interchange had three loops and a flyover ramp for southbound the eastbound traffic while the new interchange is a simple diamond. Since the Indianapolis International Airport terminal moved from near this interchange to the new midfield terminal back in 2008 the down-scaling of this interchange was appropriate. But plenty of traffic still uses this interchange especially in the southbound to eastbound movement which now requires stopping at a traffic light. It's no accident that this is one of the few intersections with three left turn lanes in Indianapolis.

I don't agree with the downgrading being appropriate, as Sam Jones makes a nice cut through between I-74 and I-70 (it may be longer but it's not the multi-signal misery of 38th Street between I-465 and I-65).  IMHO the free-flow movement from SB to EB should have been kept and the corresponding loop removed at the I-465/I-70 interchange to the south.

[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'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).

Whether the loop ramp would be built today is an interesting question. I didn't come by any traffic volumes to guess at whether a case would be made by them there–I may just not know where to search, but maybe because it's technically on I-270, it doesn't seem to have been called out in docs for the US 36 project. I agree space issues would be a significant factor; there's a lot going on in the area transportation-wise, and more to come as the express lane network develops. CDOT wants to do some widening–including, atypically, extending a GPL north of US 36 ("Element 1" here), following the addition of the interim I-25 north express lanes that ate up the shoulders. There's also a vision for a direct connection from an I-270 westbound express lane to the I-25 northbound express lane, which would take up some more vertical space and merging area.

--

Following a couple tangents on what warrants a high-capacity ramp:

Related to that interchange, when the US 36 express lane project was under development, CDOT proposed replacing the ramp from southbound I-25 to US 36 that goes through signal with a free-flowing ramp (concepts in Appendix D here, starting on pdf's page 193). It seems like a location where they might be able to finagle an elevated ramp over the parking lots, sort of in the spirit of your linked ramp, but the proposals went the route of full property acquisitions. In the end, no changes were made by the project over concerns about loss of access to Broadway; the ramp was left for further study, and I don't know of the subject being revisited. Funding to buy the properties or build new bridges for whatever ramps probably isn't out there, anyway.


Colorado has another sort of close-quarters 'triangle' of heavy-duty roads at C-470/US 6/I-70, which there are no serious plans to change. (Oh, how I wish they would, or that they had back when there was much less stuff around.) A few years ago, someone sent a question to the news about more free-flow access between US 6 and I-70, and the response was that it's not worth the expense.

In the 90s, there was some intention of grade-separating the through movements of US 6 at C-470 (see "Freeways" on page 4 here of the very much outmoded 1992 City of Golden Major Thoroughfare Plan). More recently, a northwest Denver corridor study looked into grade-separating the light rail line at Johnson Rd–there's a priority conflict between the arterial roads and keeping a schedule on the single-tracked rail line–and determined it would be cost-prohibitive.

(And, lastly, speaking of space-hogs, I've wondered if anyone had planned for a loop ramp inside the US 6 to I-70 flyover, but I haven't found anything to suggest other movements have been sketched out.)

[Bruce]

The Swamp Creek interchange really should have included a SB I-5 to NB SR 525 ramp, with braided access to Alderwood Mall Blvd. As it stands, a lot of backtracking is required to reach the mall.

[jakeroot]

The Swamp Creek interchange really should have included a SB I-5 to NB SR 525 ramp, with braided access to Alderwood Mall Blvd. As it stands, a lot of backtracking is required to reach the mall.

The access issues with Alderwood Mall do remind me a lot of the issues with Southcenter Mall, at the southern end of 405. It's easy to get off northbound 5 to access Southcenter, but getting back on to northbound 5 requires some looping around onto Southcenter Blvd. Southbound has the issue for access: either get off at Southcenter Blvd, and loop around over the 405 to access the mall, or get on to 405 and exit at West Valley Hwy (WA-181). You can even go west and loop onto 51st Ave S, go over 518, and then stay on that as it becomes Klickitat Dr which ends at the mall. Either way, not exactly direct.

The big issues seems to be the separation between the on and off ramps. They are in totally different places depending on where you are coming from and/or going to, so there's a lot of traffic that seems to be wandering around trying to figure out where the opposite ramp is from the one they used to get to the mall. At least the Alderwood interchanges are complete (apart from 5/525/405).

Still, it's all better than Alderwood, though, since at least there are interchanges in the rough vicinity. Seems like the interchanges for Alderwood Mall were designed after the fact, or there was little consideration of how traffic actually moves in the area. The fact that Alderwood Mall Pkwy passes over I-5 to the south without any freeway access is surprising to me. Not now, but maybe 20 years ago, it could have been considered for maybe an on or off-ramp. Or at the very least, yeah, there should have been access between southbound 5 and northbound 525.