"Why?" interchange designs

[kphoger]

*See what I did there?

[webny99]

*See what I did there?

2/29 is leap day. I'll see myself out.

[Rothman]

US 9/NY 73 is interesting because it was built pre-Northway for a lot more traffic on US 9 than is there now.  Most traffic these days is probably going to NY 73 from the exit on the Northway a mile south of there.

Yup, that's what I was doing when passing through this past fall. A standard T-intersection with US 9 to NY 73 as the through movement would be more than sufficient.

Nah.  I like it the way it is.   Funnels traffic from the Northway up NY 73.  It's fine as is.

[webny99]

US 9/NY 73 is interesting because it was built pre-Northway for a lot more traffic on US 9 than is there now.  Most traffic these days is probably going to NY 73 from the exit on the Northway a mile south of there.

Yup, that's what I was doing when passing through this past fall. A standard T-intersection with US 9 to NY 73 as the through movement would be more than sufficient.

Nah.  I like it the way it is.   Funnels traffic from the Northway up NY 73.  It's fine as is.

A T-intersection would do that as well if US 9 > NY 73 was the through movement.  I'm not saying it needs to be redesigned, but if it ever was, a T-intersection would work.

[MCRoads]

The Kentucky parkway system has some real oddball interchanges. There are a few where all four ramps are loop ramps for some reason, and when looking for an example of that I also came across this thing, which seems to be an inside-out folded diamond interchange. Maybe I'm missing something, but I can't see any practical reason for these designs.

Tollbooths. The idea was to have a single tollbooth in a central location accessible by all traffic. Here's the second one in 1983.

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For a modern and more robust example, see here.

Oklahoma has one remaining example of this here. There used to be another one on this same road, but the other one was converted into a conventional parclo.

[deathtopumpkins]

Oklahoma has one remaining example of this here. There used to be another one on this same road, but the other one was converted into a conventional parclo.

Oklahoma has more than one remaining example of that. There is also one on the H. E. Bailey, and two on the Cimarron [1], [2], plus half of one on the Cherokee.

[zachary_amaryllis]

The strangest one I've ever seen is still the one near Perth Amboy.

that, friend, is uglier than a truckload of pimples.

[wanderer2575]

I drove through this five-ramp parclo interchange in Shelby Township, MI yesterday.  Roundabouts were constructed at the ramp termini in the past couple years but the loop ramp was not removed.  That loop ramp is now completely redundant as northbound M-53 traffic can access either direction of 26 Mile Road from either exit ramp.  I was confused at first; I knew I wanted to go west but my GPS directed me to use the exit ramp for eastbound 26 Mile, as heading west after going through the roundabout was a few feet shorter than using the loop ramp.

[OCGuy81]

Has anyone mentioned the Ross Island Bridge clusterfu....errr....interchange in Portland, OR yet?

No?

The Ross Island mess in Portland OR. It's a hot mess to say the least. If you're looking to follow US 26 without a GPS and aren't from the area? Good luck.

[kphoger]

I drove through this five-ramp parclo interchange in Shelby Township, MI yesterday.  Roundabouts were constructed at the ramp termini in the past couple years but the loop ramp was not removed.  That loop ramp is now completely redundant as northbound M-53 traffic can access either direction of 26 Mile Road from either exit ramp.  I was confused at first; I knew I wanted to go west but my GPS directed me to use the exit ramp for eastbound 26 Mile, as heading west after going through the roundabout was a few feet shorter than using the loop ramp.

That is weird.

[webny99]

I drove through this five-ramp parclo interchange in Shelby Township, MI yesterday.  Roundabouts were constructed at the ramp termini in the past couple years but the loop ramp was not removed.  That loop ramp is now completely redundant as northbound M-53 traffic can access either direction of 26 Mile Road from either exit ramp.  I was confused at first; I knew I wanted to go west but my GPS directed me to use the exit ramp for eastbound 26 Mile, as heading west after going through the roundabout was a few feet shorter than using the loop ramp.

That is weird.

My initial thought was yes, that is weird, but the more I think about it, the more sense it makes. My guess is that the remaining loop is the busiest of the four "loop" movements. In order to prevent delays, the best alternative to leaving that loop intact would seem to be allowing left turn movements from multiple lanes, and based on the design, you can see why it's not ideal to have heavy traffic trying to make that left turn movement. They would have had to include an extra lane around that leg of the loop, and likely add a third lane to the exit ramp to prevent delays to right-turning traffic, which is also not ideal. I wouldn't even be surprised if there's something coded into state law disallowing three-lane approaches to roundabouts.

I would absolutely choose the loop ramp to make the left turn movement, personally. But here's a car doing the opposite - using the loop to make the right turn movement. Now that doesn't make any sense.

[Hwy 61 Revisited]

This monstrosity in Secaucus.




Maybe not as convoluted as others, but I'm pretty sure this is the trump card in any Longest Onramps Ever game.

[Joe The Dragon]

This monstrosity in Secaucus.




Maybe not as convoluted as others, but I'm pretty sure this is the trump card in any Longest Onramps Ever game.

https://www.google.com/maps/@41.6136102,-87.426561,1700m/data=!3m1!1e3

Not as bad and kind of an breezewood interchange

[jakeroot]

The interchange between WA-18 and WA-167 in Auburn is not bad. It works for the traffic it handles.

However, I would personally give it a "why?" stamp because although it takes a ton of land, it's still missing several maneuvers such as northbound to westbound and eastbound to southbound. Arguably the least important maneuvers but, with this much land, how did they not find a way to fit it in? Well...

WA-18 came first, alongside the interchange with West Valley Hwy. These were built around 1960. The full interchange with WA-167 came with its construction in the 1970s (then and still known as the Valley Fwy). Rather than rebuild the WA-18/West Valley Hwy interchange to free up room, it was decided to basically not touch it. That still left the state with plenty of ROW, but it doesn't seem to have been utilized all that well. Even looking at the existing movements, some of them are very unsafe (tight exits, tight merges, short weaves, weirdly shaped loop). Yet, again, so much ROW here to do something so much better.

So, to put it plainly: it's not that there isn't an explanation for why there are missing maneuvers. But WSDOT (or the preceding highway department) went the cheap route for the new interchange, and we're left today with a substandard design that takes tons of land and yet still has missing maneuvers. Brilliant.

[Hwy 61 Revisited]

The interchange between WA-18 and WA-167 in Auburn is not bad. It works for the traffic it handles.

However, I would personally give it a "why?" stamp because although it takes a ton of land, it's still missing several maneuvers such as northbound to westbound and eastbound to southbound. Arguably the least important maneuvers but, with this much land, how did they not find a way to fit it in? Well...

WA-18 came first, alongside the interchange with West Valley Hwy. These were built around 1960. The full interchange with WA-167 came with its construction in the 1970s (then and still known as the Valley Fwy). Rather than rebuild the WA-18/West Valley Hwy interchange to free up room, it was decided to basically not touch it. That still left the state with plenty of ROW, but it doesn't seem to have been utilized all that well. Even looking at the existing movements, some of them are very unsafe (tight exits, tight merges, short weaves, weirdly shaped loop). Yet, again, so much ROW here to do something so much better.

So, to put it plainly: it's not that there isn't an explanation for why there are missing maneuvers. But WSDOT (or the preceding highway department) went the cheap route for the new interchange, and we're left today with a substandard design that takes tons of land and yet still has missing maneuvers. Brilliant.

I remember you posting a redesign on the Redesigning Interchanges thread; I think maybe you should try proposing that to WSDOT.

[kernals12]

The interchange between MA 9 and Speen Street in Natick, nicknamed "The Beetleback". It must be one of the most complex arterial-arterial interchanges out there, but it's crazy enough to work. It's the only part of the Golden Triangle that isn't a traffic nightmare. It does 3 very good things:
1. It distributes traffic through a series of one way streets, which reduces the number of traffic signal phases and allows many movements to occur unsignalized.
2. It uses braided ramps, which eliminate weaving on 9
3. It has a Texas U-Turn that allows for a 3 phase signal at Natick Mall Road

[jakeroot]

The interchange between WA-18 and WA-167 in Auburn is not bad. It works for the traffic it handles.

However, I would personally give it a "why?" stamp because although it takes a ton of land, it's still missing several maneuvers such as northbound to westbound and eastbound to southbound. Arguably the least important maneuvers but, with this much land, how did they not find a way to fit it in? Well...

WA-18 came first, alongside the interchange with West Valley Hwy. These were built around 1960. The full interchange with WA-167 came with its construction in the 1970s (then and still known as the Valley Fwy). Rather than rebuild the WA-18/West Valley Hwy interchange to free up room, it was decided to basically not touch it. That still left the state with plenty of ROW, but it doesn't seem to have been utilized all that well. Even looking at the existing movements, some of them are very unsafe (tight exits, tight merges, short weaves, weirdly shaped loop). Yet, again, so much ROW here to do something so much better.

So, to put it plainly: it's not that there isn't an explanation for why there are missing maneuvers. But WSDOT (or the preceding highway department) went the cheap route for the new interchange, and we're left today with a substandard design that takes tons of land and yet still has missing maneuvers. Brilliant.

I remember you posting a redesign on the Redesigning Interchanges thread; I think maybe you should try proposing that to WSDOT.

Yeah, here.

I've thought about sending it to them, but many design cues weren't necessarily anything more than whims (made without much real evidence). I could send it, but I'd have to make some notes in the event they ask me about some of the design decisions.

[kphoger]

This monstrosity in Secaucus.

Maybe not as convoluted as others, but I'm pretty sure this is the trump card in any Longest Onramps Ever game.

2½ miles!  On the other hand, it's easy to understand why it was built that way.

[webny99]

This monstrosity in Secaucus.

Maybe not as convoluted as others, but I'm pretty sure this is the trump card in any Longest Onramps Ever game.

2½ miles!  On the other hand, it's easy to understand why it was built that way.

Bit of a different situation, but reminds me of this (3.5 miles from first crossing to second crossing) near Syracuse.

[Hwy 61 Revisited]

This monstrosity in Secaucus.

Maybe not as convoluted as others, but I'm pretty sure this is the trump card in any Longest Onramps Ever game.

2½ miles!  On the other hand, it's easy to understand why it was built that way.

Bit of a different situation, but reminds me of this (3.5 miles from first crossing to second crossing) near Syracuse.

But isn't there enough land to... like... shorten the curve??

[froggie]

^ Keep in mind that the Thruway was a ticket system and only very recently went AET.  Now that it's AET, the curve could theoretically be shortened.  But very little traffic actually makes that WB 690 to EB 90 movement.  There would also be ramp spacing issues for shortening that curve with the WB 690 on-ramp at Exit 5.

[vdeane]

^ Keep in mind that the Thruway was a ticket system and only very recently went AET.  Now that it's AET, the curve could theoretically be shortened.  But very little traffic actually makes that WB 690 to EB 90 movement.  There would also be ramp spacing issues for shortening that curve with the WB 690 on-ramp at Exit 5.

Also issues with the placement of the gantry for the exits 36-39 virtual ticket system - which is between the I-690 overpass and exit 39.

[Rothman]

You should have seen the interchange between I-90 and I-690 before it was updated.  I believe it included a traffic light.  You can still see faint scars of where the old ramps were closer to the overpass.

[roadman65]

https://goo.gl/maps/E6ePxwkJAvuJFWsP6

This interchange is really interesting.   In actuality it's really a volleyball to US 75 but a diamond with the US 75 frontage road.

[jakeroot]

https://goo.gl/maps/E6ePxwkJAvuJFWsP6

This interchange is really interesting.   In actuality it's really a volleyball to US 75 but a diamond with the US 75 frontage road.

I'm not sure I follow. Aren't all volleyball interchanges just mutations of the split diamond?