Wonder why they didn't use a SPUI at western Blvd and I-440 like they are using at I-840/Lawndale Dr.
The SPUI takes up less space and you don't have to drive on the wrong side.
I say keep DDIs for existing interchange improvements and SPUIs for a new freeway.
SPUIs take up more space in the sense that you have to have an extra-wide overpass or underpass to accommodate the left turns meeting at a singular point in the middle. DDIs are a lot easier to convert from a standard diamond, and they take up roughly the same footprint.
I see DDIs more when there are more traffic getting on the freeway than continuing on the arterial, as left turns onto the freeway are free-flow. Traffic signals are 2 phases instead of 3, though there are 2 sets of signals instead of 1. Left turns ignore the second one though as mentioned already. Also, it's easier to convert from a standard diamond or parclo.
Quote from: SkyPesos on April 18, 2021, 09:23:54 PM
I see DDIs more when there are more traffic getting on the freeway than continuing on the arterial, as left turns onto the freeway are free-flow. Traffic signals are 2 phases instead of 3, though there are 2 sets of signals instead of 1. Left turns ignore the second one though as mentioned already. Also, it's easier to convert from a standard diamond or parclo.
I'm not sure what the selling points of a SPUI are, other than a smaller footprint (since the U stands for "Urban") but the DDI, as noted above, is generally implemented when you have a large amount of traffic entering the freeway from the intersecting route.
Quote from: hbelkins on April 18, 2021, 10:04:49 PM
Quote from: SkyPesos on April 18, 2021, 09:23:54 PM
I see DDIs more when there are more traffic getting on the freeway than continuing on the arterial, as left turns onto the freeway are free-flow. Traffic signals are 2 phases instead of 3, though there are 2 sets of signals instead of 1. Left turns ignore the second one though as mentioned already. Also, it's easier to convert from a standard diamond or parclo.
I'm not sure what the selling points of a SPUI are, other than a smaller footprint (since the U stands for "Urban") but the DDI, as noted above, is generally implemented when you have a large amount of traffic entering the freeway from the intersecting route.
It's a bit easier to understand for drivers, and for me the 3 phases doesn't matter since suburban arterials in California has 4 phases anyway and there's 1 fewer light compared to DDI, parclo, or plain diamond so less delays since here the 2 signals are more often not synchronized than do..
Nowadays the Parclo B4 would be the alternative if they didn't want to go with a DDI.
Quote from: tolbs17 on April 19, 2021, 07:08:49 AM
Nowadays the Parclo B4 would be the alternative if they didn't want to go with a DDI.
I've seen a couple of B4 Parclos replaced with a DDI actually. One of them is I-70 exit 222 (Mid Rivers Mall Dr) in MO.
Quote from: SkyPesos on April 19, 2021, 08:06:31 AM
Quote from: tolbs17 on April 19, 2021, 07:08:49 AM
Nowadays the Parclo B4 would be the alternative if they didn't want to go with a DDI.
I've seen a couple of B4 Parclos replaced with a DDI actually. One of them is I-70 exit 222 (Mid Rivers Mall Dr) in MO.
BS. Why?
Quote from: tolbs17 on April 19, 2021, 08:40:39 AM
Quote from: SkyPesos on April 19, 2021, 08:06:31 AM
Quote from: tolbs17 on April 19, 2021, 07:08:49 AM
Nowadays the Parclo B4 would be the alternative if they didn't want to go with a DDI.
I’ve seen a couple of B4 Parclos replaced with a DDI actually. One of them is I-70 exit 222 (Mid Rivers Mall Dr) in MO.
BS. Why?
The WB 70 ramp onto Mid Rivers backed up onto the freeway frequently because of the left turn, as it's where the mall and other businesses are. Also, there's a left turn right south of the I-70 overpass from SB Mid Rivers to EB Veterans Memorial at the same location as the EB 70 exit ramp, and there's actually a good amount of cars coming off WB 70 using that turn, so that's one benefit of a B4 parclo gone. I moved out of the St Louis area when the Parclo was getting converted to a DDI, so I don't know how well the DDI works compared to the parclo, but the WB exit ramp changed from 2 exit only lanes to 1 exit only and 1 option lane, so I guess it worked well enough that an option lane could be used on the left instead of an exit only?
SPUIs work better for high-volume left turn movements.
Quote from: thspfc on April 19, 2021, 11:14:49 AM
SPUIs work better for high-volume left turn movements.
How is it better than a DDI for left-turn movements? You literally hug the curb when you turn left on a DDI and follow the same signal phase as thru-traffic.
Quote from: tolbs17 on April 18, 2021, 07:37:05 PM
The SPUI takes up less space and you don't have to drive on the wrong side.
1. You don't drive on the wrong side at a DDI either. You drive on the left side. And the left side is the correct side.
2. I'm pretty sure those aren't the only two factors under consideration when choosing between a list of alternatives.
Quote from: kphoger on April 19, 2021, 03:48:27 PM
Quote from: tolbs17 on April 18, 2021, 07:37:05 PM
The SPUI takes up less space and you don't have to drive on the wrong side.
1. You don't drive on the wrong side at a DDI either. You drive on the left side. And the left side is the correct side.
2. I'm pretty sure those aren't the only two factors under consideration when choosing between a list of alternatives.
How about an improved diamond interchange?
Quote from: tolbs17 on April 19, 2021, 04:56:58 PM
Quote from: kphoger on April 19, 2021, 03:48:27 PM
Quote from: tolbs17 on April 18, 2021, 07:37:05 PM
The SPUI takes up less space and you don't have to drive on the wrong side.
1. You don't drive on the wrong side at a DDI either. You drive on the left side. And the left side is the correct side.
2. I'm pretty sure those aren't the only two factors under consideration when choosing between a list of alternatives.
How about an improved diamond interchange?
Isn't that what a DDI is?
Quote from: 1995hoo on April 19, 2021, 05:00:19 PM
Quote from: tolbs17 on April 19, 2021, 04:56:58 PM
Quote from: kphoger on April 19, 2021, 03:48:27 PM
Quote from: tolbs17 on April 18, 2021, 07:37:05 PM
The SPUI takes up less space and you don't have to drive on the wrong side.
1. You don't drive on the wrong side at a DDI either. You drive on the left side. And the left side is the correct side.
2. I'm pretty sure those aren't the only two factors under consideration when choosing between a list of alternatives.
How about an improved diamond interchange?
Isn't that what a DDI is?
That's what two of the three letters stand for, after all!
Quote from: SkyPesos on April 19, 2021, 08:06:31 AM
Quote from: tolbs17 on April 19, 2021, 07:08:49 AM
Nowadays the Parclo B4 would be the alternative if they didn't want to go with a DDI.
I've seen a couple of B4 Parclos replaced with a DDI actually. One of them is I-70 exit 222 (Mid Rivers Mall Dr) in MO.
That was a parclo
A4:
(https://i.imgur.com/mPDP3Lo.png)
Quote from: 1995hoo on April 19, 2021, 05:00:19 PM
Quote from: tolbs17 on April 19, 2021, 04:56:58 PM
Quote from: kphoger on April 19, 2021, 03:48:27 PM
Quote from: tolbs17 on April 18, 2021, 07:37:05 PM
The SPUI takes up less space and you don't have to drive on the wrong side.
1. You don't drive on the wrong side at a DDI either. You drive on the left side. And the left side is the correct side.
2. I'm pretty sure those aren't the only two factors under consideration when choosing between a list of alternatives.
How about an improved diamond interchange?
Isn't that what a DDI is?
https://xfer.services.ncdot.gov/PDEA/Web/NC150/r2307_rdy_phm_psh_06.pdf
Look at this. NCDOT went with a regular diamond interchange and they did not push it to be a SPUI or a DDI.
Quote from: CtrlAltDel on April 19, 2021, 05:32:41 PM
Quote from: SkyPesos on April 19, 2021, 08:06:31 AM
Quote from: tolbs17 on April 19, 2021, 07:08:49 AM
Nowadays the Parclo B4 would be the alternative if they didn't want to go with a DDI.
I've seen a couple of B4 Parclos replaced with a DDI actually. One of them is I-70 exit 222 (Mid Rivers Mall Dr) in MO.
That was a parclo A4:
(https://i.imgur.com/mPDP3Lo.png)
I mix those two up pretty frequently, thanks. So B4 is the variant with the loop ramp off the freeway...
Though I question if a B4 parclo is better than an A4 or DDI, as you're still making a left turn getting onto the freeway. There probably is a reason why there are much more A4s out there than B4s.
Quote from: SkyPesos on April 19, 2021, 08:26:40 PM
Quote from: CtrlAltDel on April 19, 2021, 05:32:41 PM
Quote from: SkyPesos on April 19, 2021, 08:06:31 AM
Quote from: tolbs17 on April 19, 2021, 07:08:49 AM
Nowadays the Parclo B4 would be the alternative if they didn't want to go with a DDI.
I’ve seen a couple of B4 Parclos replaced with a DDI actually. One of them is I-70 exit 222 (Mid Rivers Mall Dr) in MO.
That was a parclo A4:
(https://i.imgur.com/mPDP3Lo.png)
I mix those two up pretty frequently, thanks. So B4 is the variant with the loop ramp off the freeway...
Though I question if a B4 parclo is better than an A4 or DDI, as you're still making a left turn getting onto the freeway. There probably is a reason why there are much more A4s out there than B4s.
The trick is to remember that "A" means
before and "B" means
after. Or more seriously, I've long thought that the labels should be reversed because the way they are now is far from intuitive. Or, maybe, go with "dp" for what is currently "A," and "qb" for what is currently "B," since the loop ramps combined with the mainline vaguely look like those letters. The more I think about it, the more I like this idea, sophomoric meaning of "dp" notwithstanding.
Past that, I'm sure tradephoric will be by before too long to point out the relative advantages and disadvantages of these different types of parclo, whatever label you give them.
Quote from: kphoger on April 19, 2021, 05:31:42 PM
Quote from: 1995hoo on April 19, 2021, 05:00:19 PM
Quote from: tolbs17 on April 19, 2021, 04:56:58 PM
How about an improved diamond interchange?
Isn't that what a DDI is?
That's what two of the three letters stand for, after all!
As for the third letter, though, Diverging ≠ Improved.
Or at least, they're not synonyms, even if you could argue that something could be both at once.
If exit numbers are increasing, a parclo A4 would be where an exit would have suffix A as a cloverleaf, and the same for B.
Quote from: 1 on April 19, 2021, 09:29:09 PM
If exit numbers are increasing, a parclo A4 would be where an exit would have suffix A as a cloverleaf, and the same for B.
From what I got from the thread already, I thought there generally wouldn't be exit number suffixes for A4 exits, as it's a single ramp.
A disadvantage of a SPUI interchange is that you cannot make a U-turn going in the opposite direction compared to the other interchanges.
Quote from: tolbs17 on April 19, 2021, 10:03:04 PM
A disadvantage of a SPUI interchange is that you cannot make a U-turn going in the opposite direction compared to the other interchanges.
I though SPUIs are one of the easier interchanges to make a U-turn.
I've heard SPUI's work better than DDI's when there are high through volumes on the road crossing the freeway and signal coordination is a concern.
Quote from: SkyPesos on April 19, 2021, 10:29:57 PM
Quote from: tolbs17 on April 19, 2021, 10:03:04 PM
A disadvantage of a SPUI interchange is that you cannot make a U-turn going in the opposite direction compared to the other interchanges.
I though SPUIs are one of the easier interchanges to make a U-turn.
I was thinking that too!
If this (https://www.google.com/maps/@35.6574896,-80.4608443,742m/data=!3m1!1e3) interchange was constructed today, it would have been a DDI I'm sure.
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Quote from: tolbs17 on April 19, 2021, 10:42:25 PM
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Not even small arterials for DDIs. Major arterials with tons of traffic entering or exiting the freeway compared to staying on the arterial could warrant a DDI over a SPUI.
Quote from: SkyPesos on April 19, 2021, 10:46:37 PM
Quote from: tolbs17 on April 19, 2021, 10:42:25 PM
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Not even small arterials for DDIs. Major arterials with tons of traffic entering or exiting the freeway compared to staying on the arterial could warrant a DDI over a SPUI.
That was the reasoning for the first full DDI in the Phoenix area at Happy Valley Rd and I-17.
Quote from: SkyPesos on April 19, 2021, 10:46:37 PM
Quote from: tolbs17 on April 19, 2021, 10:42:25 PM
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Not even small arterials for DDIs. Major arterials with tons of traffic entering or exiting the freeway compared to staying on the arterial could warrant a DDI over a SPUI.
In that case, I would go with a Parclo.
Quote from: ztonyg on April 19, 2021, 10:49:35 PM
Quote from: SkyPesos on April 19, 2021, 10:46:37 PM
Quote from: tolbs17 on April 19, 2021, 10:42:25 PM
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Not even small arterials for DDIs. Major arterials with tons of traffic entering or exiting the freeway compared to staying on the arterial could warrant a DDI over a SPUI.
That was the reasoning for the first full DDI in the Phoenix area at Happy Valley Rd and I-17.
Not a major highway.
Quote from: tolbs17 on April 19, 2021, 10:52:48 PM
Quote from: ztonyg on April 19, 2021, 10:49:35 PM
Quote from: SkyPesos on April 19, 2021, 10:46:37 PM
Quote from: tolbs17 on April 19, 2021, 10:42:25 PM
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Not even small arterials for DDIs. Major arterials with tons of traffic entering or exiting the freeway compared to staying on the arterial could warrant a DDI over a SPUI.
That was the reasoning for the first full DDI in the Phoenix area at Happy Valley Rd and I-17.
Not a major highway.
Is 6 lanes not wide enough for an arterial?
Quote from: SkyPesos on April 19, 2021, 10:54:01 PM
Quote from: tolbs17 on April 19, 2021, 10:52:48 PM
Quote from: ztonyg on April 19, 2021, 10:49:35 PM
Quote from: SkyPesos on April 19, 2021, 10:46:37 PM
Quote from: tolbs17 on April 19, 2021, 10:42:25 PM
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Not even small arterials for DDIs. Major arterials with tons of traffic entering or exiting the freeway compared to staying on the arterial could warrant a DDI over a SPUI.
That was the reasoning for the first full DDI in the Phoenix area at Happy Valley Rd and I-17.
Not a major highway.
Is 6 lanes not wide enough for an arterial?
Oh, it's wide. Just not an expressway design.
Quote from: tolbs17 on April 19, 2021, 10:56:54 PM
Quote from: SkyPesos on April 19, 2021, 10:54:01 PM
Quote from: tolbs17 on April 19, 2021, 10:52:48 PM
Quote from: ztonyg on April 19, 2021, 10:49:35 PM
Quote from: SkyPesos on April 19, 2021, 10:46:37 PM
Quote from: tolbs17 on April 19, 2021, 10:42:25 PM
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Not even small arterials for DDIs. Major arterials with tons of traffic entering or exiting the freeway compared to staying on the arterial could warrant a DDI over a SPUI.
That was the reasoning for the first full DDI in the Phoenix area at Happy Valley Rd and I-17.
Not a major highway.
Is 6 lanes not wide enough for an arterial?
Oh, it's wide. Just not an expressway design.
Try Bangerter Highway and SR 201 in western Salt Lake City, then. For an idea of how much traffic turns there, look how many left turn lanes there are from westbound 201. Traffic still routinely backs up onto the mainline at that exit.
Battleground Ave and Lawndale Dr, they went with a SPUI because a DDI would have taken up more space.
And like I said, SPUIs are better if the freeway goes over the arterial and if it's a new freeway rather than upgrading the existing. In that case, the DDI is better.
Look at Six Forks Rd and US 401. I'm sure those would have been built as a diverging diamond if they were built like right now.
Quote from: tolbs17 on April 19, 2021, 10:49:58 PM
Quote from: SkyPesos on April 19, 2021, 10:46:37 PM
Quote from: tolbs17 on April 19, 2021, 10:42:25 PM
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Not even small arterials for DDIs. Major arterials with tons of traffic entering or exiting the freeway compared to staying on the arterial could warrant a DDI over a SPUI.
In that case, I would go with a Parclo.
Unless you're ADOT (Arizona) which seems to hate Parclos like a passion. There are only a handful of parclos in the entire state. It's pretty much 85% diamond, 10% SPUI, and 5% other (parclo, barbell, DDI) here.
Quote from: ztonyg on April 20, 2021, 12:24:47 AM
Quote from: tolbs17 on April 19, 2021, 10:49:58 PM
Quote from: SkyPesos on April 19, 2021, 10:46:37 PM
Quote from: tolbs17 on April 19, 2021, 10:42:25 PM
SPUIs and Parclo B4s are more appropriate for main highways.
DDIs and Dumbbells (and dogbones) are for small arterials.
Not even small arterials for DDIs. Major arterials with tons of traffic entering or exiting the freeway compared to staying on the arterial could warrant a DDI over a SPUI.
In that case, I would go with a Parclo.
Unless you're ADOT (Arizona) which seems to hate Parclos like a passion. There are only a handful of parclos in the entire state. It's pretty much 85% diamond, 10% SPUI, and 5% other (parclo, barbell, DDI) here.
Sounds like the opposite of Ontario. A4 Parclos seem like the go-to there, which I don't mind, as it's a solid design. I think someone else here mentioned it yesterday in the Best Interchange Designs thread.
Look at INDOT with their full cloverleafs being converted to Parclos.
Quote from: US 89 on April 19, 2021, 11:03:13 PM
Quote from: tolbs17 on April 19, 2021, 10:56:54 PM
Quote from: SkyPesos on April 19, 2021, 10:54:01 PM
Is 6 lanes not wide enough for an arterial?
Oh, it's wide. Just not an expressway design.
Try Bangerter Highway and SR 201 in western Salt Lake City, then. For an idea of how much traffic turns there, look how many left turn lanes there are from westbound 201. Traffic still routinely backs up onto the mainline at that exit.
Could that be a problem with the signal timing? It seems ridiculous that it would still back up onto the freeway with three left turn lanes. The only comparable example I can think of is
I-490 at NY 441 (https://www.google.com/maps/@43.129494,-77.5254837,3a,90y,148.86h,68.32t/data=!3m6!1e1!3m4!1ssAqNbc1ZGx-ePxLaMjeN-g!2e0!7i16384!8i8192!5m1!1e1), and even though the right lane of I-490 is often slow approaching the exit, I've never known the line for the signal to back right up onto the freeway.
Quote from: webny99 on April 19, 2021, 09:24:32 PM
Quote from: kphoger on April 19, 2021, 05:31:42 PM
Quote from: 1995hoo on April 19, 2021, 05:00:19 PM
Quote from: tolbs17 on April 19, 2021, 04:56:58 PM
How about an improved diamond interchange?
Isn't that what a DDI is?
That's what two of the three letters stand for, after all!
As for the third letter, though, Diverging ≠ Improved.
Or at least, they're not synonyms, even if you could argue that something could be both at once.
I get it. But, if agencies didn't consider the DDI to be an improvement, then they wouldn't design them at all. After all, a standard diamond interchange (SDI?) is cheaper.
Quote from: kphoger on April 20, 2021, 10:08:27 AM
Quote from: webny99 on April 19, 2021, 09:24:32 PM
Quote from: kphoger on April 19, 2021, 05:31:42 PM
Quote from: 1995hoo on April 19, 2021, 05:00:19 PM
Quote from: tolbs17 on April 19, 2021, 04:56:58 PM
How about an improved diamond interchange?
Isn't that what a DDI is?
That's what two of the three letters stand for, after all!
As for the third letter, though, Diverging ≠ Improved.
Or at least, they're not synonyms, even if you could argue that something could be both at once.
I get it. But, if agencies didn't consider the DDI to be an improvement, then they wouldn't design them at all. After all, a standard diamond interchange (SDI?) is cheaper.
And of course, there are
many different aspects of "improved", traffic flow and safety being chief among them. You could argue - and I'm sure people have - that the DDI improves some aspects but not others.
Would the SPUI or DDI be better for the US 17/70 and Dr. MLK JR Blvd interchange in New Bern?
Quote from: tolbs17 on April 19, 2021, 11:48:04 PM
Battleground Ave and Lawndale Dr, they went with a SPUI because a DDI would have taken up more space.
And like I said, SPUIs are better if the freeway goes over the arterial and if it's a new freeway rather than upgrading the existing. In that case, the DDI is better.
Look at Six Forks Rd and US 401. I'm sure those would have been built as a diverging diamond if they were built like right now.
More space? Maybe for one of those jumbo things a lot of DOTs seem to install for whatever reason, but they don't have to take up any more room than a standard diamond (https://www.google.com/maps/@43.1075346,-77.5756574,296m/data=!3m1!1e3).
Quote from: vdeane on April 20, 2021, 12:33:06 PM
Quote from: tolbs17 on April 19, 2021, 11:48:04 PM
Battleground Ave and Lawndale Dr, they went with a SPUI because a DDI would have taken up more space.
And like I said, SPUIs are better if the freeway goes over the arterial and if it's a new freeway rather than upgrading the existing. In that case, the DDI is better.
Look at Six Forks Rd and US 401. I'm sure those would have been built as a diverging diamond if they were built like right now.
More space? Maybe for one of those jumbo things a lot of DOTs seem to install for whatever reason, but they don't have to take up any more room than a standard diamond (https://www.google.com/maps/@43.1075346,-77.5756574,296m/data=!3m1!1e3).
Those are wider interchanges compared to the one on friendly avenue
Quote from: tolbs17 on April 20, 2021, 02:26:16 PM
Quote from: vdeane on April 20, 2021, 12:33:06 PM
Quote from: tolbs17 on April 19, 2021, 11:48:04 PM
Battleground Ave and Lawndale Dr, they went with a SPUI because a DDI would have taken up more space.
And like I said, SPUIs are better if the freeway goes over the arterial and if it's a new freeway rather than upgrading the existing. In that case, the DDI is better.
Look at Six Forks Rd and US 401. I'm sure those would have been built as a diverging diamond if they were built like right now.
More space? Maybe for one of those jumbo things a lot of DOTs seem to install for whatever reason, but they don't have to take up any more room than a standard diamond (https://www.google.com/maps/@43.1075346,-77.5756574,296m/data=!3m1!1e3).
Those are wider interchanges compared to the one on friendly avenue
Friendly Avenue? :confused:
Quote from: vdeane on April 20, 2021, 08:36:06 PM
Quote from: tolbs17 on April 20, 2021, 02:26:16 PM
Quote from: vdeane on April 20, 2021, 12:33:06 PM
Quote from: tolbs17 on April 19, 2021, 11:48:04 PM
Battleground Ave and Lawndale Dr, they went with a SPUI because a DDI would have taken up more space.
And like I said, SPUIs are better if the freeway goes over the arterial and if it's a new freeway rather than upgrading the existing. In that case, the DDI is better.
Look at Six Forks Rd and US 401. I'm sure those would have been built as a diverging diamond if they were built like right now.
More space? Maybe for one of those jumbo things a lot of DOTs seem to install for whatever reason, but they don't have to take up any more room than a standard diamond (https://www.google.com/maps/@43.1075346,-77.5756574,296m/data=!3m1!1e3).
Those are wider interchanges compared to the one on friendly avenue
Friendly Avenue? :confused:
I-73 exit 104. Also, it's an SPUI, not a DDI as I imagined based on the context here.
Ah. Hard to tell what that is when "Friendly Avenue" hasn't been mentioned elsewhere in this thread by name. In any case, the difference in the width of that interchange and the one I posted seems to be median width; looking at my example and the distance the ramp is from the freeway mainline, I'm sure it would be just as narrow if the freeway ROW was the same width.
Quote from: tolbs17 on April 20, 2021, 12:31:24 AM
Look at INDOT with their full cloverleafs being converted to Parclos.
Isn't that common with a lot of DOTs now; converting full cloverleafs from a freeway to arterial to some other interchange? US 40's exits to US 67, Hampton and Kingshighway in St Louis all got converted to SPUIs as part of a complete rebuild of the freeway 13 years ago. I-270's interchange with US 67 had one of the loop ramps replaced with a signal, and will be converted to a split diamond in the coming years.
Quote from: SkyPesos on April 20, 2021, 09:14:22 PM
Quote from: tolbs17 on April 20, 2021, 12:31:24 AM
Look at INDOT with their full cloverleafs being converted to Parclos.
Isn't that common with a lot of DOTs now; converting full cloverleafs from a freeway to arterial to some other interchange? US 40's exits to US 67, Hampton and Kingshighway in St Louis all got converted to SPUIs as part of a complete rebuild of the freeway 13 years ago. I-270's interchange with US 67 had one of the loop ramps replaced with a signal, and will be converted to a split diamond in the coming years.
But look at I-295 in Virginia.
Quote from: tolbs17 on April 20, 2021, 09:46:03 PM
Quote from: SkyPesos on April 20, 2021, 09:14:22 PM
Quote from: tolbs17 on April 20, 2021, 12:31:24 AM
Look at INDOT with their full cloverleafs being converted to Parclos.
Isn't that common with a lot of DOTs now; converting full cloverleafs from a freeway to arterial to some other interchange? US 40's exits to US 67, Hampton and Kingshighway in St Louis all got converted to SPUIs as part of a complete rebuild of the freeway 13 years ago. I-270's interchange with US 67 had one of the loop ramps replaced with a signal, and will be converted to a split diamond in the coming years.
But look at I-295 in Virginia.
Which point(s) on I-295? It's 53 miles long.
Quote from: SkyPesos on April 20, 2021, 09:48:51 PM
Quote from: tolbs17 on April 20, 2021, 09:46:03 PM
Quote from: SkyPesos on April 20, 2021, 09:14:22 PM
Quote from: tolbs17 on April 20, 2021, 12:31:24 AM
Look at INDOT with their full cloverleafs being converted to Parclos.
Isn't that common with a lot of DOTs now; converting full cloverleafs from a freeway to arterial to some other interchange? US 40's exits to US 67, Hampton and Kingshighway in St Louis all got converted to SPUIs as part of a complete rebuild of the freeway 13 years ago. I-270's interchange with US 67 had one of the loop ramps replaced with a signal, and will be converted to a split diamond in the coming years.
But look at I-295 in Virginia.
Which point(s) on I-295? It's 53 miles long.
All of it. Most of it is cloverleafs.
Quote from: tolbs17 on April 20, 2021, 09:51:36 PM
Quote from: SkyPesos on April 20, 2021, 09:48:51 PM
Quote from: tolbs17 on April 20, 2021, 09:46:03 PM
Quote from: SkyPesos on April 20, 2021, 09:14:22 PM
Quote from: tolbs17 on April 20, 2021, 12:31:24 AM
Look at INDOT with their full cloverleafs being converted to Parclos.
Isn't that common with a lot of DOTs now; converting full cloverleafs from a freeway to arterial to some other interchange? US 40's exits to US 67, Hampton and Kingshighway in St Louis all got converted to SPUIs as part of a complete rebuild of the freeway 13 years ago. I-270's interchange with US 67 had one of the loop ramps replaced with a signal, and will be converted to a split diamond in the coming years.
But look at I-295 in Virginia.
Which point(s) on I-295? It's 53 miles long.
All of it. Most of it is cloverleafs.
Seems like Virginia have a love affair with cloverleafs in general. Found a lot of them in the NoVA area too.
Quote from: SkyPesos on April 20, 2021, 09:56:08 PM
Quote from: tolbs17 on April 20, 2021, 09:51:36 PM
Quote from: SkyPesos on April 20, 2021, 09:48:51 PM
Quote from: tolbs17 on April 20, 2021, 09:46:03 PM
Quote from: SkyPesos on April 20, 2021, 09:14:22 PM
Quote from: tolbs17 on April 20, 2021, 12:31:24 AM
Look at INDOT with their full cloverleafs being converted to Parclos.
Isn't that common with a lot of DOTs now; converting full cloverleafs from a freeway to arterial to some other interchange? US 40's exits to US 67, Hampton and Kingshighway in St Louis all got converted to SPUIs as part of a complete rebuild of the freeway 13 years ago. I-270's interchange with US 67 had one of the loop ramps replaced with a signal, and will be converted to a split diamond in the coming years.
But look at I-295 in Virginia.
Which point(s) on I-295? It's 53 miles long.
All of it. Most of it is cloverleafs.
Seems like Virginia have a love affair with cloverleafs in general. Found a lot of them in the NoVA area too.
If it was NCDOT doing that project it would have all been regular or parclos.
Btw, this (https://www.google.com/maps/place/W+Friendly+Ave,+Greensboro,+NC/@36.0004664,-79.7929125,446m/data=!3m1!1e3!4m5!3m4!1s0x88531b8faeb24c43:0x1ebdd5edcf57db83!8m2!3d36.0908372!4d-79.8599776) one is also a standard diamond, will probably be modified to a DDI in the future.
Quote from: SkyPesos on April 20, 2021, 09:56:08 PM
Seems like Virginia have a love affair with cloverleafs in general.
Have you ever taken a trip to Illinois before by chance?
Quote from: JoePCool14 on April 20, 2021, 11:39:51 PM
Quote from: SkyPesos on April 20, 2021, 09:56:08 PM
Seems like Virginia have a love affair with cloverleafs in general.
Have you ever taken a trip to Illinois before by chance?
Yes :D
I had to check myself on google maps for the Chicago area interchanges, and there's way more full cloverleafs than I initially thought. I still think Virginia wins the cloverleafs count though. The Metro East area (St Louis Illinois suburbs) have a lot of whatever these interchanges (https://www.google.com/maps/@38.6146279,-90.0497052,16.26z) are called (folded diamonds? idk).
Quote from: stridentweasel on April 18, 2021, 09:18:59 PM
DDIs are a lot easier to convert from a standard diamond, and they take up roughly the same footprint.
But this reason only applies to conversion to DDI from an existing interchange (specifically, it costs less because replacement of the existing bridge(s) is not required). I'm not sure if there's really a good reason to build a DDI from scratch when a SPUI is also considered.
Quote from: SkyPesos on April 20, 2021, 11:54:39 PM
The Metro East area (St Louis Illinois suburbs) have a lot of whatever these interchanges (https://www.google.com/maps/@38.6146279,-90.0497052,16.26z) are called (folded diamonds? idk).
(https://i.imgur.com/dbaAHw1.png)
I would call this a folded diamond, but you could also call it a parclo AB2. I wouldn't though. I tend to only use the expression "parclo" for interchanges where loop ramps supplement the straight ramps and not replace them. But that's just me, and we all know that I have strong feelings about the names given to interchanges.
So, I'm going to hop into this conversation and give you this:
https://goo.gl/maps/X1amjZeW7gKUYqyD9
See, DDIs are fairly hard to screw up. The design is pretty standard, even for weird alignments. The spur though, can be various sizes, shapes and forms. THAT? That is NOT what a SPUI should look like. The whole POINT of a SPUI is to have 3 phases, Thru, Freeway On, and Freeway Off (unless it's one of those ones where the service road has a thru movement, but with those you just add a Service Rd Thru phase). With that, coming off the freeway may be without issue, but if you're turning onto it, we'll, I'll leave that as an exercise for the reader.
Honestly, though, this would be a perfect place for a DDI, no significant ramp adjustments are needed, and basically the construction would be:
Make slight adjustments to left-turn on ramps,
Close road overnight for restriping/new traffic pattern,
Install concrete islands directing traffic,
Finalize interchange.
Converting some interchanges to DDIs requires slit more work. And if MD hasn't put in any DDIs, this could be the perfect test bed.
Quote from: MCRoads on April 21, 2021, 10:01:15 AM
So, I'm going to hop into this conversation and give you this:
https://goo.gl/maps/X1amjZeW7gKUYqyD9
See, DDIs are fairly hard to screw up. The design is pretty standard, even for weird alignments. The spur though, can be various sizes, shapes and forms. THAT? That is NOT what a SPUI should look like. The whole POINT of a SPUI is to have 3 phases, Thru, Freeway On, and Freeway Off (unless it's one of those ones where the service road has a thru movement, but with those you just add a Service Rd Thru phase). With that, coming off the freeway may be without issue, but if you're turning onto it, we'll, I'll leave that as an exercise for the reader.
As far as I can tell that SPUI still uses just three phases.
1. left turns from the ramps.
2. eastbound Allentown Rd including left turns.
3. westbound Allentown Rd including left turns.
Quote from: CtrlAltDel on April 21, 2021, 01:18:23 AM
Quote from: SkyPesos on April 20, 2021, 11:54:39 PM
The Metro East area (St Louis Illinois suburbs) have a lot of whatever these interchanges (https://www.google.com/maps/@38.6146279,-90.0497052,16.26z) are called (folded diamonds? idk).
(https://i.imgur.com/dbaAHw1.png)
I would call this a folded diamond, but you could also call it a parclo AB2. I wouldn't though. I tend to only use the expression "parclo" for interchanges where loop ramps supplement the straight ramps and not replace them. But that's just me, and we all know that I have strong feelings about the names given to interchanges.
Folded diamond. Typically used when there is some sort of geological feature (river) or other factor (railroad) that makes a normal diamond impractical or more expensive.
Quote from: hbelkins on April 21, 2021, 11:38:13 AM
Quote from: CtrlAltDel on April 21, 2021, 01:18:23 AM
Quote from: SkyPesos on April 20, 2021, 11:54:39 PM
The Metro East area (St Louis Illinois suburbs) have a lot of whatever these interchanges (https://www.google.com/maps/@38.6146279,-90.0497052,16.26z) are called (folded diamonds? idk).
(https://i.imgur.com/dbaAHw1.png)
I would call this a folded diamond, but you could also call it a parclo AB2. I wouldn't though. I tend to only use the expression "parclo" for interchanges where loop ramps supplement the straight ramps and not replace them. But that's just me, and we all know that I have strong feelings about the names given to interchanges.
Folded diamond. Typically used when there is some sort of geological feature (river) or other factor (railroad) that makes a normal diamond impractical or more expensive.
Like see 264 at downing rd and black creek.
I realized the link was the wrong coordinates. It's the interchange at I-85 and S Elm Eugene St. That interchange opened in 2004.
Quote from: tolbs17 on April 21, 2021, 12:02:00 PM
Quote from: hbelkins on April 21, 2021, 11:38:13 AM
Quote from: CtrlAltDel on April 21, 2021, 01:18:23 AM
Quote from: SkyPesos on April 20, 2021, 11:54:39 PM
The Metro East area (St Louis Illinois suburbs) have a lot of whatever these interchanges (https://www.google.com/maps/@38.6146279,-90.0497052,16.26z) are called (folded diamonds? idk).
(https://i.imgur.com/dbaAHw1.png)
I would call this a folded diamond, but you could also call it a parclo AB2. I wouldn't though. I tend to only use the expression "parclo" for interchanges where loop ramps supplement the straight ramps and not replace them. But that's just me, and we all know that I have strong feelings about the names given to interchanges.
Folded diamond. Typically used when there is some sort of geological feature (river) or other factor (railroad) that makes a normal diamond impractical or more expensive.
Like see 264 at downing rd and black creek.
I don't see a Downing Rd or a Black Creek at either of the I-264 variants. The Louisville 264 have a folded diamond near the airport though.
Quote from: SkyPesos on April 21, 2021, 12:23:33 PM
Quote from: tolbs17 on April 21, 2021, 12:02:00 PM
Like see 264 at downing rd and black creek.
I don't see a Downing Rd or a Black Creek at either of the I-264 variants. The Louisville 264 have a folded diamond near the airport though.
Given where tolbs17 lives, it might be US 264.
Quote from: 1 on April 21, 2021, 12:37:10 PM
Given where tolbs17 lives ...
Pet peeve of mine. Sorry guys, but don't post something vague and then expect me to determine where it is based on where you live. That means I have to look at your profile (if you even have your location listed), assume you're not on vacation and posting about wherever you happen to be at the time, then break out a map and figure it out myself. Chances are, I'm just not that interested in whatever you have to say to make it worth it. Just include a Google Maps link and make life easier for the rest of us. Then we might actually enter the discussion.
[/rant]
Quote from: kphoger on April 21, 2021, 12:43:28 PM
Quote from: 1 on April 21, 2021, 12:37:10 PM
Given where tolbs17 lives ...
Pet peeve of mine. Sorry guys, but don't post something vague and then expect me to determine where it is based on where you live. That means I have to look at your profile (if you even have your location listed), assume you're not on vacation and posting about wherever you happen to be at the time, then break out a map and figure it out myself. Chances are, I'm just not that interested in whatever you have to say to make it worth it. Just include a Google Maps link and make life easier for the rest of us. Then we might actually enter the discussion.
[/rant]
Agreed.
I looked, it's US-264 near Wilson, NC.
Black Creek - https://www.google.com/maps/@35.674038,-77.9062037,939m/data=!3m1!1e3
Downing Rd - https://www.google.com/maps/@35.6958441,-77.9748382,1183m/data=!3m1!1e3
Quote from: kphoger on April 21, 2021, 12:43:28 PM
Quote from: 1 on April 21, 2021, 12:37:10 PM
Given where tolbs17 lives ...
Pet peeve of mine. Sorry guys, but don't post something vague and then expect me to determine where it is based on where you live. That means I have to look at your profile (if you even have your location listed), assume you're not on vacation and posting about wherever you happen to be at the time, then break out a map and figure it out myself. Chances are, I'm just not that interested in whatever you have to say to make it worth it. Just include a Google Maps link and make life easier for the rest of us. Then we might actually enter the discussion.
[/rant]
I was at work and was using my phone...
Quote from: tolbs17 on April 21, 2021, 03:11:41 PM
I was at work and was using my phone...
Then give context, like a town name or something.
Don't just throw out "264 at downing rd and black creek" in reply to a post whose only geographical context was metro Saint Louis, then expect us to know you're talking about Wilson County, NC.
Quote from: kphoger on April 21, 2021, 12:43:28 PM
Quote from: 1 on April 21, 2021, 12:37:10 PM
Given where tolbs17 lives ...
Pet peeve of mine. Sorry guys, but don't post something vague and then expect me to determine where it is based on where you live. That means I have to look at your profile (if you even have your location listed), assume you're not on vacation and posting about wherever you happen to be at the time, then break out a map and figure it out myself. Chances are, I'm just not that interested in whatever you have to say to make it worth it. Just include a Google Maps link and make life easier for the rest of us. Then we might actually enter the discussion.
[/rant]
Thanks for saying that. :clap: Without context it would be reasonable to assume I-264 rather than US 264.
How is a Parclo A4/B4 better than a DDI and SPUI?
Quote from: tolbs17 on July 24, 2021, 04:31:30 PM
How is a Parclo A4/B4 better than a DDI and SPUI?
There's never one blanket answer. An interchange design is chosen based on traffic, roadway feature, volume, etc
True. But if I were to give a blanket answer anyways:
* parclos have fewer conflict points than SPUIs or DDIs;
* parclos are more easily implemented along signalized corridors as they have very simple phasing;
* parclos allow for non-signalized operation (B4 in particular); the vast majority of SPUIs and DDIs are signalized (maybe all but a handful) (unsignalized B4 (https://goo.gl/maps/UpDtw5fUcKEXkcX9A), unsignalized A4 (https://goo.gl/maps/ZEZkqqovYhb5UEDz8)).
My general preference is for B4 parclos over A4 parclos; B4's have left turns, which are harder to implement on existing, potentially narrow bridges, but are simpler to operate than the A4's left turns that require both directions to stop. Additionally, the B4 has better traffic distribution (traffic turning left stays left, traffic turning right stays right) compared to A4s which have all movements on the right-most lanes (sometimes better, to be fair).
Quote from: jakeroot on July 24, 2021, 10:22:47 PM
My general preference is for B4 parclos over A4 parclos; B4's have left turns, which are harder to implement on existing, potentially narrow bridges, but are simpler to operate than the A4's left turns that require both directions to stop. Additionally, the B4 has better traffic distribution (traffic turning left stays left, traffic turning right stays right) compared to A4s which have all movements on the right-most lanes (sometimes better, to be fair).
Huh, so you prefer the less common one of the two. I don't think I've ever seen a B4 parclo, almost always A4.
The advantages of SPUIs compared to other interchanges is when turning left, it's easier for big vehicles such as trucks, buses, and RVs to turn easier without making a wider turn.
And the next advantage is that of where you stop, is only in one junction. No need to stop twice compared to the other interchanges.
NCDOT still builds SPUIs, like the one at I-295 and US-401 in Western Fayetteville, although they consider it more if the highway is going over the arterial. Although in general it's more expensive. That's just a fact.
Quote from: SkyPesos on July 24, 2021, 10:32:20 PM
Quote from: jakeroot on July 24, 2021, 10:22:47 PM
My general preference is for B4 parclos over A4 parclos; B4's have left turns, which are harder to implement on existing, potentially narrow bridges, but are simpler to operate than the A4's left turns that require both directions to stop. Additionally, the B4 has better traffic distribution (traffic turning left stays left, traffic turning right stays right) compared to A4s which have all movements on the right-most lanes (sometimes better, to be fair).
Huh, so you prefer the less common one of the two. I don't think I've ever seen a B4 parclo, almost always A4.
I've heard the A4 is preferred because of concerns around tip-over with the B4 off-ramp using a loop, but I've always considered that an old wives tale.
I live very close to a
B4 parclo here in Tacoma (https://goo.gl/maps/4osfLgXeyJhsLYwLA), converted from an old cloverleaf. It flows ridiculously well, and I have never seen anything tip over using the loop. I did some extensive Googling and can't find evidence of it occurring either.
Quote from: SkyPesos on July 24, 2021, 10:32:20 PM
Huh, so you prefer the less common one of the two. I don't think I've ever seen a B4 parclo, almost always A4.
Have you not been to Xenia? US 35/US 42 interchange is a B4.
Quote from: tolbs17 on July 24, 2021, 04:31:30 PM
How is a Parclo A4/B4 better than a DDI and SPUI?
Because |tradephoric| says so.
Quote from: kphoger on July 25, 2021, 05:29:03 PM
Quote from: tolbs17 on July 24, 2021, 04:31:30 PM
How is a Parclo A4/B4 better than a DDI and SPUI?
Because |tradephoric| says so.
But this (https://www.google.com/maps/@35.0288798,-79.0404268,15.37z) interchange isn't one of them.
Quote from: tolbs17 on July 25, 2021, 05:30:57 PM
Quote from: kphoger on July 25, 2021, 05:29:03 PM
Quote from: tolbs17 on July 24, 2021, 04:31:30 PM
How is a Parclo A4/B4 better than a DDI and SPUI?
Because |tradephoric| says so.
But this (https://www.google.com/maps/@35.0288798,-79.0404268,15.37z) interchange isn't one of them.
What does that have to do with |tradephoric|?
Quote from: kphoger on July 25, 2021, 06:09:40 PM
Quote from: tolbs17 on July 25, 2021, 05:30:57 PM
Quote from: kphoger on July 25, 2021, 05:29:03 PM
Quote from: tolbs17 on July 24, 2021, 04:31:30 PM
How is a Parclo A4/B4 better than a DDI and SPUI?
Because |tradephoric| says so.
But this (https://www.google.com/maps/@35.0288798,-79.0404268,15.37z) interchange isn't one of them.
What does that have to do with |tradephoric|?
Because he's against these type of interchanges.
Tradephoric says so, but I would tend to agree as well. Parclos are literally a cheap cloverleaf that has been modified to remove the weaving, replacing it with two (or possibly zero) signals that are easily implemented along a corridor. It really is a genius design that definitely is not efficient on space but is otherwise pretty neat. DDIs and SPUIs are certainly popular because they are easily crammed in to tight ROW, but I don't think that means they are appropriate everywhere. If there is room for free-flow, there is no reason to not go that route.
My main beef with SPUIs is that they rarely support permissive lefts. I seem to be the only roadgeek who appreciates the ability to turn through gaps.
Quote from: tolbs17 on July 25, 2021, 06:23:17 PM
Because he's against these type of interchanges.
That may be, but your random link to a North Carolina SPUI is non-sequitur: it had nothing to do with
kphoger's point that Parclos are better because "tradephoric says so".
Quote from: froggie on July 25, 2021, 08:46:45 AM
Quote from: SkyPesos on July 24, 2021, 10:32:20 PM
Huh, so you prefer the less common one of the two. I don't think I've ever seen a B4 parclo, almost always A4.
Have you not been to Xenia? US 35/US 42 interchange is a B4.
Been there. My mind was blank, as A4 Parclos seem much more familiar to me. Drove past another B4 Parclo today at I-69 and IN 46. Also, the I-376 and US 22/PA 60 interchange (which I've been through before too) is a B4 parclo with a missing movement.
I like the Parclo B4 as it performs better in nearly every measure of performance compared to the Parclo A4.
(https://i.imgur.com/cy0uLvf.png)
COMPARATIVE ANALYSIS BETWEEN THE DIVERGING DIAMOND INTERCHANGE AND PARTIAL CLOVERLEAF INTERCHANGE USING MICROSIMULATION MODELING
http://fau.digital.flvc.org/islandora/object/fau%3A3779
I could see how a B4 would work better than an A4 thinking about it. The through traffic on the surface road only have to deal with one traffic signal in the interchange, instead of two signals in an A4.
^ On the chart above, what's the difference between a DDI-4 and a DDI-6?
^ It's in the literature tradephoric linked to. DDI-X refers to X number of through lanes on the cross road.
Quote from: SkyPesos on July 26, 2021, 09:04:42 AM
I could see how a B4 would work better than an A4 thinking about it. The through traffic on the surface road only have to deal with one traffic signal in the interchange, instead of two signals in an A4.
^ On the chart above, what's the difference between a DDI-4 and a DDI-6?
The 4 and 6 represent the number of through lanes at the DDI. The Parclo models had 4 though lanes with either an acceleration lane (Parclo B4) or deceleration lane (Parclo A4) on the bridge deck. The DDI models didn't include a deceleration lane on the bridge deck so the researchers decided to include a DDI-6 model as the number of bridge deck lanes would be the same as the Parclo models. However, there are plenty of Parclo B4s that don't have an acceleration lane over the bridge while there are also plenty of DDIs that do have a deceleration lane over the bridge. While i question the fairness of the methodology, the Parclo B4 model still performed exceptionally well.
I'm afraid to go through a DDI, fearing that I'll accidentally go onto the right side of the road (which in this case would be wrong). Give me the SPUI any day.
Two massive interchanges from Florida, a DDI and a Parclo B4. The I-75/Sheridan interchange was recently constructed and i think it would have been a perfect location for a contraflow Parclo B4. The advantageous of this design are:
*traffic turning left onto the freeway only have to navigate one traffic signal as opposed to two.
*traffic turning left onto the freeway only have to cross 3-lanes of traffic as opposed to 5-lanes.
*prevents left-turns from gridlocking when queues back up into the intersection.
*it's kick ass!
(https://i.imgur.com/vsJeGEe.jpg)
https://www.youtube.com/watch?v=0v1QPaYISFA&t=15s
One other design feature that I particularly like about B4 Parclos is two off-ramps rather than just one. This provides two separate areas for vehicle storage, massively reducing the chance of vehicles backing up onto the freeway. Parclo B4's can be free-flowing, but assuming a pedestrian-friendly, NTOR multiple-turn lane design, you would want a lot of storage. And you definitely get that with two separate ramps. Free-flow ramps can overwhelm the arterial, and a single off-ramp can backup to the mainline (A4 style), but a signalized design meets in the middle.
There are three B4-style off-ramps here in Tacoma, but only one has fully-signalized off-ramps. Here at 74th (https://www.google.com/maps/@47.1901846,-122.4631196,881m/data=!3m1!1e3), you can see the off-ramp split. Total off-ramp length from the gore point of I-5 Southbound to both stop lines is ~ 3430 feet, or just under two-thirds of a mile (the double right to westbound 74th is a rare-for-WA double-right NTOR). For a relatively tight urban design, it's remarkably efficient. Needless to say, backups to the mainline simply do not occur. It was built in the 80s (note the overpass is a ridiculous eight lanes), but certainly may never need rebuilding ever again.
I guess this (https://www.google.com/maps/@35.6800019,-77.9537307,16.08z)interchange would be called a "Parclo B3".
While that interchange looks overbuilt, 80% of the traffic uses the loop to exit.
https://ncdot.maps.arcgis.com/home/webmap/viewer.html?webmap=b7a26d6d8abd419f8c27f58a607b25a1
Exiting a freeway at an unsignalized Parclo A4 (https://www.google.com/maps/@40.4345801,-88.9908737,3a,90y,87.6h,76.08t/data=!3m6!1e1!3m4!1sRIHQ18ynXbnqR1buuhRCww!2e0!7i13312!8i6656) versus
entering a freeway at an unsignalized Parclo B4 (https://www.google.com/maps/@30.4107108,-81.7466609,3a,75y,124.21h,85.73t/data=!3m6!1e1!3m4!1swC_woYpBPbkkwR3BOKLOxw!2e0!7i16384!8i8192). As a driver which would you rather encounter? The turning movements at a Parclo B4 interchange are simple and helps explain why there are so many unsignalized Parclo B4s.
Quote from: jakeroot on July 27, 2021, 12:54:34 AM
One other design feature that I particularly like about B4 Parclos is two off-ramps rather than just one. This provides two separate areas for vehicle storage, massively reducing the chance of vehicles backing up onto the freeway.
I do like the added off ramp queue space the Parclo B4 provides. In addition, the Parclo B4 only has one on ramp with traffic merging onto the freeway as opposed to two at a Parclo A4. Limiting the number of on ramps where traffic is merging onto the freeway sounds like a net benefit for safety too.
Quote from: Henry on July 26, 2021, 11:05:58 AM
I'm afraid to go through a DDI, fearing that I'll accidentally go onto the right side of the road (which in this case would be wrong). Give me the SPUI any day.
Having driven through both kinds plenty of times, I actually worry about conflicting with oncoming traffic at a SPUI
more than I do at a DDI. I've never once been at all unclear about where to go at any DDI I've used.
Quote from: tolbs17 on July 27, 2021, 04:41:37 AM
I guess this (https://www.google.com/maps/@35.6800019,-77.9537307,16.08z)interchange would be called a "Parclo B3".
While that interchange looks overbuilt, 80% of the traffic uses the loop to exit.
https://ncdot.maps.arcgis.com/home/webmap/viewer.html?webmap=b7a26d6d8abd419f8c27f58a607b25a1
You need to check your link. Google Maps might be better than ArcGIS Online.
Quote from: tradephoric on July 27, 2021, 07:47:41 AM
Quote from: jakeroot on July 27, 2021, 12:54:34 AM
One other design feature that I particularly like about B4 Parclos is two off-ramps rather than just one. This provides two separate areas for vehicle storage, massively reducing the chance of vehicles backing up onto the freeway.
I do like the added off ramp queue space the Parclo B4 provides. In addition, the Parclo B4 only has one on ramp with traffic merging onto the freeway as opposed to two at a Parclo A4. Limiting the number of on ramps where traffic is merging onto the freeway sounds like a net benefit for safety too.
Certainly possible. Having a single on ramp seems like it might help with queue management as well, especially when used in tandem with ramp meters. Rather than setups
like this (https://goo.gl/maps/PyWBY7gZJNvTEXvS8), where one ramp could become much busier than the other, with no way for one ramp to relieve the other.
I would contend the opposite issue (queue management issues with multiple off-ramps) is less problematic as you can add turn lanes, improve signal timing, add roundabouts, etc to improve flow onto the arterial if it actually becomes a problem (rare from my experience). Freeways are rather sacred in comparison and need to be managed more carefully, due to high speeds and limited "creative" alternative design options.
Quote from: tolbs17 on July 27, 2021, 04:41:37 AM
I guess this (https://www.google.com/maps/@35.6800019,-77.9537307,16.08z)interchange would be called a "Parclo B3".
While that interchange looks overbuilt, 80% of the traffic uses the loop to exit.
https://ncdot.maps.arcgis.com/home/webmap/viewer.html?webmap=b7a26d6d8abd419f8c27f58a607b25a1
I'm seeing a four-quadrant interchange with a loop ramp beyond the crossroad. Using the typical Ontario terminology, that would make it a B4, not a B3.
Quote from: jakeroot on July 27, 2021, 01:15:18 PM
Quote from: tolbs17 on July 27, 2021, 04:41:37 AM
I guess this (https://www.google.com/maps/@35.6800019,-77.9537307,16.08z)interchange would be called a "Parclo B3".
While that interchange looks overbuilt, 80% of the traffic uses the loop to exit.
https://ncdot.maps.arcgis.com/home/webmap/viewer.html?webmap=b7a26d6d8abd419f8c27f58a607b25a1
You need to check your link. Google Maps might be better than ArcGIS Online.
I went ahead and zoomed in. Specifically, 81%
of the total exiting traffic on eastbound US-264 uses the loop ramp (to US-301 North), with the remaining 19% using the direct ramp (to US-301 South).
But |tolbs17| is missing the bigger picture: the on-ramp there has an AADT that's 40% higher
than both of them put together. If you moved the loop ramp to the other side of US-301, changing it from B4 to A4 configuration, then the loop ramp would be carrying 88% more traffic than the adjacent off-ramp–which you might notice is more than the existing 81% difference.
For what it's worth, exiting traffic is only 8% of the total eastbound US-264 traffic., and the AADT of the existing loop ramp is only 1500.
Quote from: kphoger on July 27, 2021, 01:41:01 PM
Quote from: jakeroot on July 27, 2021, 01:15:18 PM
Quote from: tolbs17 on July 27, 2021, 04:41:37 AM
I guess this (https://www.google.com/maps/@35.6800019,-77.9537307,16.08z)interchange would be called a "Parclo B3".
While that interchange looks overbuilt, 80% of the traffic uses the loop to exit.
https://ncdot.maps.arcgis.com/home/webmap/viewer.html?webmap=b7a26d6d8abd419f8c27f58a607b25a1
You need to check your link. Google Maps might be better than ArcGIS Online.
I went ahead and zoomed in. Specifically, 81% of the total exiting traffic on eastbound US-264 uses the loop ramp (to US-301 North), with the remaining 19% using the direct ramp (to US-301 South).
But |tolbs17| is missing the bigger picture: the on-ramp there has an AADT that's 40% higher than both of them put together. If you moved the loop ramp to the other side of US-301, changing it from B4 to A4 configuration, then the loop ramp would be carrying 88% more traffic than the adjacent off-ramp–which you might notice is more than the existing 81% difference.
For what it's worth, exiting traffic is only 8% of the total eastbound US-264 traffic., and the AADT of the existing loop ramp is only 1500.
Interesting. When I open the link, the ArcGIS map's extent is set to the entire state of North Carolina. I only was able to find the interchange in question thanks to your comments (US-264 @ US-301).
As to your observation: I completely agree that the overall picture is key to correctly assessing the success of an interchange. To be fair, such an assessment may actually show A4 parclos to be better under certain circumstances: perhaps there is so much entering traffic that having only one on-ramp with traffic taking turns is going to be worse for flow than an on-ramp loop and adjacent direct right turn ramp. But, such a situation seems much less common, and backups from a single off-ramp (A4 style) seem like a bigger issue that is more easily addressed with off-ramp loops and direct ramps.
Quote from: jakeroot on July 27, 2021, 01:58:45 PM
When I open the link, the ArcGIS map's extent is set to the entire state of North Carolina. I only was able to find the interchange in question thanks to your comments (US-264 @ US-301).
Same here. I got the location from his hyperlink, then found that location on the NCDOT map and zoomed in.
Quote from: kphoger on July 27, 2021, 02:02:21 PM
Quote from: jakeroot on July 27, 2021, 01:58:45 PM
When I open the link, the ArcGIS map's extent is set to the entire state of North Carolina. I only was able to find the interchange in question thanks to your comments (US-264 @ US-301).
Same here. I got the location from his hyperlink, then found that location on the NCDOT map and zoomed in.
:pan: :pan: I'm an idiot. I didn't notice that "this" was a hyperlink in his original post. I was trying to find the Parclo using the ArcGIS map.
THIS is why I'm glad you and I underline our links by default. So much easier to spot.
Quote from: jakeroot on July 27, 2021, 02:03:47 PM
I didn't notice that "this" was a hyperlink in his original post.
THIS is why I'm glad you and I underline our links by default. So much easier to spot.
:awesomeface: Glad to know someone noticed!
And there's another interchange close by. So some traffic uses that one as well. While AADT might not look high enough to warrant signals, you are crossing a wide 6-lane boulevard therefore that's why it's signalized.
Quote from: tolbs17 on July 27, 2021, 03:02:19 PM
And there's another interchange close by. So some traffic uses that one as well. While AADT might not look high enough to warrant signals, you are crossing a wide 6-lane boulevard therefore that's why it's signalized.
What? No one at the interchange you posted is crossing six lanes, apart from the westbound off-ramp. The eastbound on-ramp only crosses three lanes, and there is no inherent need for a signal crossing three lanes unless there is enough oncoming traffic to back up left turning traffic regularly enough to require at least part-time protection. Basically what already exists.
Unless you
are referring to the westbound off-ramp. But then I'm not sure why you would since no one is talking about it.
Here's an unsignalized Parclo B4 (https://www.google.com/maps/@26.0627809,-80.3503012,3a,75y,67.57h,82.44t/data=!3m7!1e1!3m5!1sOjP_rNhlKxAZ_vkPS-q-iA!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DOjP_rNhlKxAZ_vkPS-q-iA%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D62.29504%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192) along a 6-lane boulevard in Florida.
Quote from: tradephoric on July 27, 2021, 03:16:45 PM
Here's an unsignalized Parclo B4 (https://www.google.com/maps/@26.0627809,-80.3503012,3a,75y,67.57h,82.44t/data=!3m7!1e1!3m5!1sOjP_rNhlKxAZ_vkPS-q-iA!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DOjP_rNhlKxAZ_vkPS-q-iA%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D62.29504%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192) along a 6-lane boulevard in Florida.
talking about if you are
exiting the highway.
Quote from: tolbs17 on July 27, 2021, 03:02:19 PM
And there's another interchange close by. So some traffic uses that one as well. While AADT might not look high enough to warrant signals, you are crossing a wide 6-lane boulevard therefore that's why it's signalized.
I don't think any of us (except perhaps you) has suggested the interchange shouldn't have signals. We've just been talking about the A/B configuration of the ParClo.
Quote from: kphoger on July 27, 2021, 03:39:41 PM
Quote from: tolbs17 on July 27, 2021, 03:02:19 PM
And there's another interchange close by. So some traffic uses that one as well. While AADT might not look high enough to warrant signals, you are crossing a wide 6-lane boulevard therefore that's why it's signalized.
I don't think any of us (except perhaps you) has suggested the interchange shouldn't have signals. We've just been talking about the A/B configuration of the ParClo.
Now check out the ParClo B4 near Sims. Do you think that interchange is overbuilt?
Quote from: tolbs17 on July 27, 2021, 03:41:49 PM
Now check out the ParClo B4 near Sims. Do you think that interchange is overbuilt?
Are you going to provide a Google Maps link? Or even a freaking state name? Because
this (https://goo.gl/maps/d6MCL5ubsT4b9CBR9) is the only Sims I'm familiar with.
Quote from: kphoger on July 27, 2021, 03:45:10 PM
Quote from: tolbs17 on July 27, 2021, 03:41:49 PM
Now check out the ParClo B4 near Sims. Do you think that interchange is overbuilt?
Are you going to provide a Google Maps link? Or even a freaking state name? Because this (https://goo.gl/maps/d6MCL5ubsT4b9CBR9) is the only Sims I'm familiar with.
6297 US-264 ALT
https://maps.app.goo.gl/wZ9bB9m2CvMZ8Uzc9
Quote from: tolbs17 on July 27, 2021, 03:46:45 PM
Quote from: kphoger on July 27, 2021, 03:45:10 PM
Quote from: tolbs17 on July 27, 2021, 03:41:49 PM
Now check out the ParClo B4 near Sims. Do you think that interchange is overbuilt?
Are you going to provide a Google Maps link? Or even a freaking state name? Because this (https://goo.gl/maps/d6MCL5ubsT4b9CBR9) is the only Sims I'm familiar with.
6297 US-264 ALT
https://maps.app.goo.gl/wZ9bB9m2CvMZ8Uzc9
Ehhh, maybe not. The southwestern loop ramp has an AADT of 4400, so it's probably justified. And the northeastern loop ramp avoids left turns onto US-264-Alt, which has an AADT of 15,500 there.
Quote from: kphoger on July 27, 2021, 03:45:10 PM
Quote from: tolbs17 on July 27, 2021, 03:41:49 PM
Now check out the ParClo B4 near Sims. Do you think that interchange is overbuilt?
Are you going to provide a Google Maps link? Or even a freaking state name? Because this (https://goo.gl/maps/d6MCL5ubsT4b9CBR9) is the only Sims I'm familiar with.
There's this one (https://www.google.com/maps/@42.6415759,-71.3096405,3a,75y,166.93h,83.53t/data=!3m7!1e1!3m5!1sp4k2w6okibafd0SKuxhyLA!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3Dp4k2w6okibafd0SKuxhyLA%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D266.6981%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192) too, although it's only a business and not a city.
Quote from: tolbs17 on July 27, 2021, 03:41:49 PM
Now check out the ParClo B4 near Sims. Do you think that interchange is overbuilt?
Why are you always worried about interchanges being overbuilt? Partial Cloverleafs are literally just cloverleafs with even fewer ramps. Apart from the land they can take (less for partial variations, mind you), cloverleafs are considered very unobtrusive, as they require only a single overpass or underpass, and are only two levels. That interchange near Sims would qualify as overbuilt, IMO, if there were multiple left turn lanes, traffic signals, maybe even a flyover...but what's there now is far from overbuilt.
Quote from: jakeroot on July 27, 2021, 05:12:02 PM
Quote from: tolbs17 on July 27, 2021, 03:41:49 PM
Now check out the ParClo B4 near Sims. Do you think that interchange is overbuilt?
Why are you always worried about interchanges being overbuilt? Partial Cloverleafs are literally just cloverleafs with even fewer ramps. Apart from the land they can take (less for partial variations, mind you), cloverleafs are considered very unobtrusive, as they require only a single overpass or underpass, and are only two levels. That interchange near Sims would qualify as overbuilt, IMO, if there were multiple left turn lanes, traffic signals, maybe even a flyover...but what's there now is far from overbuilt.
Because they just pay more for nothing. But back from 1999-2003 most to all traffic had to exit there to get on US-264 East since the Wilson bypass was done in two phases. The southbound ramps were signalized as well.
Quote from: tolbs17 on December 18, 2021, 02:58:00 PM
Because they just pay more for nothing.
I feel like this is a rather gross generalization. I think what you're seeing in NC is simply preparation for expected growth, particularly in regards to the partial cloverleafs which are a great way to preserve right of way without overspending (they are relatively cheap as they don't have flyovers).
Are there any websites for a SPUI interchange like there is with a DDI interchange and a roundabout interchange like here?
https://roundabouts.kittelson.com/
Quote from: tolbs17 on December 24, 2021, 06:37:39 PM
Are there any websites for a SPUI interchange like there is with a DDI interchange and a roundabout interchange like here?
https://roundabouts.kittelson.com/
Somebody can post one and prove me wrong, but I feel like they are too common for that. Utah alone currently has 38 SPUIs with at least five more in various stages of construction/planning.
I realize that site has a roundabouts database and those are way more common than even SPUIs, but there are so many that a dataset like that will quickly become inaccurate and out of date.
Quote from: US 89 on January 04, 2022, 12:59:20 PM
Quote from: tolbs17 on December 24, 2021, 06:37:39 PM
Are there any websites for a SPUI interchange like there is with a DDI interchange and a roundabout interchange like here?
https://roundabouts.kittelson.com/
Somebody can post one and prove me wrong, but I feel like they are too common for that. Utah alone currently has 38 SPUIs with at least five more in various stages of construction/planning.
Ah. Well we have like 10-15 or so here. We still build them it just depends on the circumstances of where one would fit the best.
A SPUI is currently planned here (https://www.google.com/maps/@35.9131202,-78.7827431,1244m/data=!3m1!1e3), and another one here (https://www.google.com/maps/@35.2348162,-77.5644417,768m/data=!3m1!1e3)which came from the NC 11/NC 58 relocation but that was from a feasibility study so it might never happen.
https://connect.ncdot.gov/projects/planning/Pages/FeasibilityStudyDocuments.aspx#InplviewHash956c0103-f47f-4f71-9192-dec1d2976da5=SortField%3DYear-SortDir%3DDesc-FilterField1%3DCounty-FilterValue1%3DLenoir
Skip to pages 22 and 26 for more details.
Quote from: tolbs17 on December 24, 2021, 06:37:39 PM
Are there any websites for a SPUI interchange like there is with a DDI interchange and a roundabout interchange like here?
https://roundabouts.kittelson.com/
While by no means complete, here is a KMZ file of roughly 160 USA SPUIs:
https://www.mediafire.com/file/frrld5uhdwr2klp/SPUI.kmz/file
Quote from: tradephoric on January 04, 2022, 02:37:34 PM
Quote from: tolbs17 on December 24, 2021, 06:37:39 PM
Are there any websites for a SPUI interchange like there is with a DDI interchange and a roundabout interchange like here?
https://roundabouts.kittelson.com/
While by no means complete, here is a KMZ file of roughly 160 USA SPUIs:
https://www.mediafire.com/file/frrld5uhdwr2klp/SPUI.kmz/file
Definitely misses a lot of them after looking at it.