This forum is for complaining about cloverleafs and for finding ways to make them better.
iPhone
How do I submit the form?
Collector/distributor roads.
And where's the form?
Also...
This (https://goo.gl/maps/FFnAzbh7B1HaFfWaA).
Similar footprint, two bridges instead of one, no weaving
Quote from: kphoger on April 19, 2019, 03:46:10 PM
This (https://goo.gl/maps/FFnAzbh7B1HaFfWaA).
Similar footprint, two bridges instead of one, no weaving
The left entrances seem problematic here.
Quote from: Amtrakprod on April 19, 2019, 03:24:24 PM
This form is for complaining about cloverleafs and for finding ways to make them better.
iPhone
No traffic lights...free flowing traffic...nothing wrong with them. If they're placed in a high-volume area they will probably fail...but so will many other interchange designs.
Quote from: CtrlAltDel on April 19, 2019, 03:54:24 PM
Quote from: kphoger on April 19, 2019, 03:46:10 PM
This (https://goo.gl/maps/FFnAzbh7B1HaFfWaA).
Similar footprint, two bridges instead of one, no weaving
The left entrances seem problematic here.
Which is more problematic, though? Weaving or left entrances?
Quote from: kphoger on April 19, 2019, 03:57:01 PM
Quote from: CtrlAltDel on April 19, 2019, 03:54:24 PM
Quote from: kphoger on April 19, 2019, 03:46:10 PM
This (https://goo.gl/maps/FFnAzbh7B1HaFfWaA).
Similar footprint, two bridges instead of one, no weaving
The left entrances seem problematic here.
Which is more problematic, though? Weaving or left entrances?
Left entrances. Cloverleaf weaving affects one lane; trying to take a quick right exit after entering on the left requires crossing multiple lanes (although it might not be as much of a problem here).
Quote from: kphoger on April 19, 2019, 03:46:10 PM
Also...
This (https://goo.gl/maps/FFnAzbh7B1HaFfWaA).
Similar footprint, two bridges instead of one, no weaving
This also puts curves on one of the intersecting roads.
A cloverleaf-like design that could fit in the same/marginally larger footprint (from my youtube channel):
One of the biggest benefits of cloverleafs is you only need one short overpass, I think the cost effectiveness of cloverleafs is very hard to beat.
Left exits are OK, left entrances not so much. I hate I-66 west to I-81 south.
For low-volume cloverleafs, CD lanes help. For higher-volume ones, like I-64/I-265, you need flyovers.
Quote from: kphoger on April 19, 2019, 03:33:56 PM
Collector/distributor roads.
That would obviously be the single option that adds the most value, i.e. most benefit for the cost.
There is something similar - but simpler, as it doesn't involve a secondary roadway - used on I-90 in Buffalo: A lane for the second (loop) exit opens
prior to the loop
entrance ramp coming in, thus allowing traffic exiting at the loop to decelerate first and then merge with entering traffic, instead of doing both at once. Then said lane extends
after the loop ramp exits as well, allowing entering traffic an opportunity to accelerate.
In the absence of a full c/d road, the above is the absolute minimum that should be done. Come to think of it, it's actually really strange it's not done more often; a few hundred feet of pavement on either side of the weave hardly costs anything, while making a world of difference for keeping the mainline flowing freely.
The problem I have is the weaving.
I've always liked this design (I-395 and VA-7 in Alexandria, Virginia) (https://www.google.com/maps/@38.8340426,-77.0975902,16.97z). Relocates two of the loop-around ramps, and alters the approach to the remaining two, to eliminate the weave areas. I suppose it might be slightly more expensive due to the additional overpasses, but on the other hand it may be suitable for tighter spaces.
A much more expensive solution, implemented as part of the Wilson Bridge reconstruction project, can be seen on the north side of the interchange of the Beltway and Telegraph Road near Alexandria (https://www.google.com/maps/@38.8007984,-77.0785162,446m/data=!3m1!1e3): One of the loop ramps uses an overpass to clear the other one, eliminating the weave area. (The south side of this interchange has been redesigned, but it never had two loop ramps because there was always a flyover ramp there, just not in the current configuration. Flyovers are never going to be the solution to all cloverleafs.)
Quote from: 1995hoo on April 20, 2019, 09:08:55 AM
A much more expensive solution, implemented as part of the Wilson Bridge reconstruction project, can be seen on the north side of the interchange of the Beltway and Telegraph Road near Alexandria (https://www.google.com/maps/@38.8007984,-77.0785162,446m/data=!3m1!1e3): One of the loop ramps uses an overpass to clear the other one, eliminating the weave area. (The south side of this interchange has been redesigned, but it never had two loop ramps because there was always a flyover ramp there, just not in the current configuration. Flyovers are never going to be the solution to all cloverleafs.)
There's always the braided loop option that MNDOT used for I-694 at MN 252 (https://goo.gl/maps/kWgPvwUpepezhC9N6)
It's also worth noting that it has become increasingly common to replace cloverleafs with diamonds when one of the roads is not a freeway. There are three examples on I-35 in Kansas alone: Exit 183 for SB US 59; Exit 228B for EB US 56, NB US 69/US 169, and Shawnee Mission Parkway; and Exit 232B for NB US 69 and Roe Avenue.
My personal opinion is that, for interchanges where a free-flowing interchange is justified, the most cost-effective solution is to add C/D lanes and tighten the inner loop ramps (so no additional land acquisition is required). Flyover ramps only become justified when certain left-turning movements through the interchange play a major role in the traffic flow of the surrounding area.
Convert them to something like this.
(https://mainframere.com/wp-content/uploads/2015/05/i-4-toll-expansion-render-maitland-030413.jpg)
https://www.google.com/maps/@28.63102,-81.38741,777m/data=!3m1!1e3
https://www.youtube.com/watch?v=B8DUMjlKqx8
Quote from: tradephoric on April 22, 2019, 08:11:10 AM
Convert them to something like this.
(https://mainframere.com/wp-content/uploads/2015/05/i-4-toll-expansion-render-maitland-030413.jpg)
https://www.google.com/maps/@28.63102,-81.38741,777m/data=!3m1!1e3
https://www.youtube.com/watch?v=B8DUMjlKqx8
Should people be physically blocked from making a u-turn? Or do people have good enough sense not to do it? Or is it sometimes permissible?
^So I'm assuming if someone takes the wrong turn you want them to be able to make a U-turn directly within the interchange design itself? I don't think this would be necessary and/or common in these type of designs. Here are some additional real-world examples of them:
https://www.google.com/maps/@33.91199,-84.35671,735m/data=!3m1!1e3
https://www.google.com/maps/@39.6990515,-86.1485446,810m/data=!3m1!1e3
https://www.google.com/maps/@35.47833,-97.57863,721m/data=!3m1!1e3
https://www.google.com/maps/@35.51118,-97.57637,721m/data=!3m1!1e3
https://www.google.com/maps/@28.3460328,-81.5333474,779m/data=!3m1!1e3
Quote from: tradephoric on April 22, 2019, 08:11:10 AM
Convert them to something like this.
(https://mainframere.com/wp-content/uploads/2015/05/i-4-toll-expansion-render-maitland-030413.jpg)
https://www.google.com/maps/@28.63102,-81.38741,777m/data=!3m1!1e3
https://www.youtube.com/watch?v=B8DUMjlKqx8
The only issue I've got here are the left exits. Interchange designs like these have been used for decades, and they have caused problems, slower traffic impeding the left lane to exit, a load of traffic trying to merge on all at once, slowing traffic way down, increasing accident chances, etc. Why it's still being used is beyond me.
Quote from: sprjus4 on April 22, 2019, 04:40:29 PM
Quote from: tradephoric on April 22, 2019, 08:11:10 AM
Convert them to something like this.
(https://mainframere.com/wp-content/uploads/2015/05/i-4-toll-expansion-render-maitland-030413.jpg)
https://www.google.com/maps/@28.63102,-81.38741,777m/data=!3m1!1e3
https://www.youtube.com/watch?v=B8DUMjlKqx8
The only issue I've got here are the left exits. Interchange designs like these have been used for decades, and they have caused problems, slower traffic impeding the left lane to exit, a load of traffic trying to merge on all at once, slowing traffic way down, increasing accident chances, etc. Why it's still being used is beyond me.
That design is no different than a parclo B4, except that there's a free-flow movement instead of a direct left turn across oncoming traffic. Add that to the fact that Maitland isn't really a freeway, and I don't have any issues with something like this.
Quote from: sprjus4 on April 22, 2019, 04:40:29 PM
The only issue I've got here are the left exits. Interchange designs like these have been used for decades, and they have caused problems, slower traffic impeding the left lane to exit, a load of traffic trying to merge on all at once, slowing traffic way down, increasing accident chances, etc. Why it's still being used is beyond me.
To me having left entrance/ext ramps aren't that problematic when they are along the arterial street (or even a state highway with speed limits of 55 mph or below). Often traffic along an arterial can get jammed up approaching the freeway if both freeway on-ramps are on the right-hand side. By having a left-turn ramp you can distribute traffic more evenly along the main arterial. This example isn't a bad design to me as this is a freeway to arterial interchange.... people have to learn when to freak out about left-turn entrance/exits and when not to...
https://www.google.com/maps/@35.47833,-97.57863,721m/data=!3m1!1e3
Who can fix the cloverleaf while still retaining its most attractive elements?
only two bridge decks (assuming a dual carriageway)
all right entrances and exits
Quote from: kphoger on April 22, 2019, 07:05:44 PM
Who can fix the cloverleaf while still retaining its most attractive elements?
only two bridge decks (assuming a dual carriageway)
all right entrances and exits
Some variant on the roundabout in West Drayton (UK). There are similar designs for I-93 at MA 213 (no fourth leg, but one could be created if the geometry was modified slightly) and I-95 at US 1 in Topsfield, MA (the inside ramps could easily be moved to the outside, but the "change direction" ramps on US 1 aren't high speed).
Quote from: kphoger on April 22, 2019, 07:05:44 PM
Who can fix the cloverleaf while still retaining its most attractive elements?
only two bridge decks (assuming a dual carriageway)
all right entrances and exits
A volleyball interchange does that, but with left turns, which are no better than loop ramps.
With a super-wide median, you could get rid of all left exits
or entrances, but not both.
Quote from: 1 on April 22, 2019, 07:17:42 PM
Quote from: kphoger on April 22, 2019, 07:05:44 PM
Who can fix the cloverleaf while still retaining its most attractive elements?
only two bridge decks (assuming a dual carriageway)
all right entrances and exits
Some variant on the roundabout in West Drayton (UK).
Where are you talking about? All I see in West Drayton are roundabout-under-motorway interchanges, which have stoplights and (by nature of roundabouts) inside "entrances/exits".
Quote from: webny99 on April 22, 2019, 07:32:12 PM
A volleyball interchange does that
A volleyball interchange fulfills none of the elements of a cloverleaf: it's not free-flowing, it has multiple bridge decks, and it has left turns.
Quote from: kphoger on April 22, 2019, 08:51:47 PM
Quote from: 1 on April 22, 2019, 07:17:42 PM
Quote from: kphoger on April 22, 2019, 07:05:44 PM
Who can fix the cloverleaf while still retaining its most attractive elements?
only two bridge decks (assuming a dual carriageway)
all right entrances and exits
Some variant on the roundabout in West Drayton (UK).
Where are you talking about? All I see in West Drayton are roundabout-under-motorway interchanges, which have stoplights and (by nature of roundabouts) inside "entrances/exits".
I was looking at where the M4 intersects itself. However, I was only looking at the map, so I didn't see the stoplights.
Quote from: 1 on April 22, 2019, 08:56:28 PM
I was looking at where the M4 intersects itself. However, I was only looking at the map, so I didn't see the stoplights.
You mean at the A408 & Heathrow (interchange #4)? Yeah, that's just a roundabout interchange, functionally no different than a dogbone.
Replace the busier movements with flyover or flyunder ramps, and keep the others. That's what was done at the junction of U.S. 29 and MD-200 (ICC) (https://www.google.com/maps/place/39%C2%B004'40.5%22N+76%C2%B057'09.3%22W/@39.077929,-76.9613487,1941m/data=!3m1!1e3!4m14!1m7!3m6!1s0x89b7c53c2de460c3:0x7a7216413ba1b0ba!2sSilver+Spring,+MD+20904!3b1!8m2!3d39.0533891!4d-76.9758274!3m5!1s0x0:0x0!7e2!8m2!3d39.0779291!4d-76.952594) in the Silver Spring area of Montgomery County, Maryland. Interchange opened to traffic in about 2011, and so far it works well.
Removing just one leaf of a cloverleaf can reduce weave issues, as was done at the junction of I-495 and MD-97 (https://www.google.com/maps/place/39%C2%B000'48.3%22N+77%C2%B002'30.8%22W/@39.013419,-77.0440677,486m/data=!3m2!1e3!4b1!4m14!1m7!3m6!1s0x89b7c53c2de460c3:0x7a7216413ba1b0ba!2sSilver+Spring,+MD+20904!3b1!8m2!3d39.0533891!4d-76.9758274!3m5!1s0x0:0x0!7e2!8m2!3d39.0134189!4d-77.0418794), also in Silver Spring.
Making them bigger would fix a lot of issues. I think if the leaves were bigger it would give you more room to weave more safely. Also collector lanes fix a lot of issues. In my opinion the I-22 / I-269 interchange in Mississippi (southeast of Memphis, TN) is the perfect cloverleaf.
I also like what they did on I-80 at its interchange with I-180 in Pennsylvania. They made the bridges on I-80 wide enough to support 4 lanes and built the collector lanes in a more cost effective manner.
The biggest issues with cloverleafs in my experiences are them causing slow downs in the right lane and causing everyone to shift over to the left lane. Traffic speeding from (typically) 25 to 70 or slowing down from 70 to 25 is also a little dangerous especially with the weaving. Collector lanes seem to fix these issues and in some cases collector lanes will have slower speed limits. I know in Danville, IL, the collector lanes at the I-74 / US 150 interchange have a 40 mph speed limit.
Quote from: cpzilliacus on April 22, 2019, 10:03:42 PM
Removing just one leaf of a cloverleaf can reduce weave issues, as was done at the junction of I-495 and MD-97 (https://www.google.com/maps/place/39%C2%B000'48.3%22N+77%C2%B002'30.8%22W/@39.013419,-77.0440677,486m/data=!3m2!1e3!4b1!4m14!1m7!3m6!1s0x89b7c53c2de460c3:0x7a7216413ba1b0ba!2sSilver+Spring,+MD+20904!3b1!8m2!3d39.0533891!4d-76.9758274!3m5!1s0x0:0x0!7e2!8m2!3d39.0134189!4d-77.0418794), also in Silver Spring.
Agreed. For a freeway to arterial interchange, cloverleafs should be changed to either a parclo a4 or parclo b4. I wish that the 495/Georgia interchange be changed to a full parclo a4, so that there is one exit (instead of two) from the inner loop. There are already traffic signals stopping traffic on both sides of Georgia anyway.
THe problem, of course, is the sequence of exit, entrance, exit, entrance that produces weaving. Far better to have exit, exit, entrance, entrance and this can be done with some kind of braided cloverleaf or eliminating one of the middle two ramps by parclo.
Freeway to freeway interchanges can be modified with well-placed flyovers or well-placed left side entrances and exits. Left side entrances and exits certainly have issues, but IMO if the left lane entrance becomes its own lane on the highway (i.e. no forced merge) then there isn't any real problem. Left side exits are even less problematic.
The Houston area has a lot of these.
Another interchange more familiar to me is in Sherman Oaks, CA. There, 405 exit ramps to the right and then merges into the left lane of 101. (This is for both of the "left turn" movements from 405 to 101). Since the exit becomes its own lane, there is no immediate merging issues. Of course, it would be difficult to merge if you need to take the next exit, so people in the know would only transfer from 405 to 101 left if driving at least 2 miles (exit at White Oak westbound or Woodman eastbound or beyond). If I wanted to go from 405 N to 101 N to Balboa, I might instead just stay on 405 and exit at a surface street like Burbank or Victory and just take surface streets to Balboa to avoid the merges. If I'm taking 405 to 101 and driving to Calabasas or further, the interchange works fine.
https://www.google.com/maps/place/Sherman+Oaks,+Los+Angeles,+CA/@34.1586198,-118.4721994,16z/data=!4m5!3m4!1s0x80c297dba79cbcf3:0x39b4e3f8071ff16!8m2!3d34.1489719!4d-118.451357
Here is a nearby example of a braided cloverleaf at 170 at Victory Blvd:
https://www.google.com/maps/place/Sherman+Oaks,+Los+Angeles,+CA/@34.187033,-118.4037058,16z/data=!4m5!3m4!1s0x80c297dba79cbcf3:0x39b4e3f8071ff16!8m2!3d34.1489719!4d-118.451357
Quote from: kphoger on April 22, 2019, 08:51:47 PM
Quote from: webny99 on April 22, 2019, 07:32:12 PM
A volleyball interchange does that
A volleyball interchange fulfills none of the elements of a cloverleaf: it's not free-flowing, it has multiple bridge decks, and it has left turns.
Shoot, I wasn't thinking about the additional bridge decks until I looked at one on a map.
While it does have left
turns, it has all right entrances and exits from the freeway mainlines, so it still fulfills one of your two requirements.
Well, I think the best way to save a cloverleaf interchange is to add flyover ramps. Interestingly, if most (or all) of the loop ramps with flyovers, may become a clover stack, or a full stack.
It seems to me that every suggested improvement other than C/D roads would replace rather than improve the cloverleaf. If an interchange is using a cloverleaf it's because it doesn't deserve something better :biggrin:
Quote from: yand on April 24, 2019, 02:57:43 PM
It seems to me that every suggested improvement other than C/D roads would replace rather than improve the cloverleaf. If an interchange is using a cloverleaf it's because it doesn't deserve something better :biggrin:
Not necessarily. A cloverleaf is a very old design and was the standard for freeway to freeway interchanges for a long time. Plus, flyover ramps greatly increase the cost as you add bridges over the whole interchange. For the most part, a cloverleaf has one freeway bridged over the other (true of every fwy to fwy interchange) and then every other movement is connected via a ramp that does not bridge over other movements. In that regard, the cloverleaf is cheaper than something like a stack.
Many cloverleafs should be replaced with something else, but often times, the DOTs lack the money. Cloverleaf to parclo conversions are relatively inexpensive since you are keeping most of what is there, but this won't work on a fwy to fwy interchange.
EDITED TO ADD:
There is a thread in Pac SW about 880/101. This is an old interchange in San Jose. Many of the loop movements are no longer so important because of newer freeways like 237 and 280 that short cut some of the movements. Also, some of the movements can be rerouted onto surface streets, as is currently done with Old Bayshore Hwy. Obviously not ideal, but if a loop movement that causes a lot of weaving (but doesn't carry much traffic) is simply eliminated it may improve mainline traffic.
https://www.aaroads.com/forum/index.php?board=29.0
And yes, it is cheaper to sign a surface street connector than to add a flyover.
(https://i.imgur.com/AfAAUXj.png)
Obviously, this would have limited application.
Quote from: kphoger on April 25, 2019, 05:18:58 PM
(https://i.imgur.com/AfAAUXj.png)
Obviously, this would have limited application.
But it would work at a fwy/arterial interchange where the arterial has a wide enough ROW for Michigan lefts. Basically combine parclo b4 with a Michigan left. No need to turn across traffic to the fwy entrance, use the Mich left instead.
And as far as "arterials" go, this could even work for some types of semi-freeways like Jersey freeways, expressways, and other semi-limited roadways that aren't full freeways, but still want to restrict signals and cross traffic as much as possible
Don't forget about the braided cloverleaf:
Quote from: Mapmikey on May 13, 2016, 07:23:45 PM
Here is US 50's cloverleaf with I-495 in Merrifield VA with braided ramps utilized for a SPUI interchange on each side of the Beltway...
https://goo.gl/maps/mQ21ejB8Yct
Quote from: jakeroot on April 03, 2018, 01:37:22 AM
In Washington, the highest volume cloverleaf would almost certainly be the 167/405 cloverleaf. There's an overpass for one of the movements, but the movement is still a loop, and the interchange is still very recognisable as a cloverleaf. At all times of day (even at 2 am), the southbound to southbound cloverleaf (the one with the overpass) backs up well before the interchange. Some directional ramps for the HOV lanes should help improve things next year:
https://goo.gl/VZy5bL
(https://i.imgur.com/bST4XBz.png)
and a California example:
https://www.google.com/maps/@34.1866034,-118.4009598,17.5z
Quote from: 1995hoo on April 20, 2019, 09:08:55 AM
I've always liked this design (I-395 and VA-7 in Alexandria, Virginia) (https://www.google.com/maps/@38.8340426,-77.0975902,16.97z). Relocates two of the loop-around ramps, and alters the approach to the remaining two, to eliminate the weave areas. I suppose it might be slightly more expensive due to the additional overpasses, but on the other hand it may be suitable for tighter spaces.
My exit...use it every day :sombrero:
EDIT: Since you're talking DC area, what do you think about the North Cap Street cloverleaf (https://www.google.com/maps/@38.9315345,-77.0085404,17z)? I always thought this was totally random...the only cloverleaf in the city, and it's not even on a freeway.
Quote from: AlexandriaVA on April 25, 2019, 08:29:10 PMSince you're talking DC area, what do you think about the North Cap Street cloverleaf (https://www.google.com/maps/@38.9315345,-77.0085404,17z) ? I always thought this was totally random...the only cloverleaf in the city, and it's not even on a freeway.
Above-Google Map link fixed; had to place a space between the parenthesis and the question mark to get the link to go to the right location.
IMO, Cloverleafs at less busy interchanges (where a rural interstate meets a rural interstate for example), aren't bad. When there are cloverleaf ramps where there should be flyovers, that's dangerous.
Quote from: kphoger on April 25, 2019, 05:18:58 PM
(https://i.imgur.com/AfAAUXj.png)
Obviously, this would have limited application.
Isn't something similar already in use in Mexico?
Lends itself to all sorts of TWSS-type jokes. If you drive through the cloverbone, does that make you a boner?
Quote from: kphoger on April 19, 2019, 03:33:56 PM
Collector/distributor roads.
I'd like to see that on the Bruckner Expressway between Buckner Boulevard and Gun Hill Road (or Baychester Avenue), but with no access to the Pelham Parkway and Hutchinson River Parkway interchanges.
Quote from: Brandon on April 26, 2019, 05:45:38 PM
Quote from: kphoger on April 25, 2019, 05:18:58 PM
(https://i.imgur.com/AfAAUXj.png)
Obviously, this would have limited application.
Isn't something similar already in use in Mexico?
There's this: https://goo.gl/maps/RLfUJmjzXiuXfrCLA
Ramps for the right-turn movements between the expressway and the crossing arterial, and jughandles on the arterial to complete the left-turn movements.
Quote from: PHLBOS on April 26, 2019, 04:42:18 PM
Quote from: AlexandriaVA on April 25, 2019, 08:29:10 PMSince you're talking DC area, what do you think about the North Cap Street cloverleaf (https://www.google.com/maps/@38.9315345,-77.0085404,17z) ? I always thought this was totally random...the only cloverleaf in the city, and it's not even on a freeway.
Above-Google Map link fixed; had to place a space between the parenthesis and the question mark to get the link to go to the right location.
A cloverleaf is not necessary here. It should be converted to a parclo a4 or a diamond. Especially annoying, is the ramp from Cap SB to Irving WB to access the hospitals. The only upside to a cloverleaf is that no direction faces signals, yet a signal is necessary here to stop WB traffic.
Also, it would be nice if more E-W thru traffic were encouraged to take Irving instead of Michigan so that N Cap traffic would not be stopped at the Michigan signal. I would even go so far as encouraging all Michigan traffic to turn onto N Cap to prevent thru traffic. N Cap is an effective semi-expressway that avoids all major cross-streets (by using overpasses) between H in Downtown and Missouri Ave except for Michigan Ave. Since there is no freeway serving the north-central area, this is the closest thing we have to an effective traffic corridor to get us to Downtown quickly.
^^^^
I think I've only passed through that cloverleaf once. Normally if I'm in that area I'll turn right from northbound North Capitol onto Michigan to head to the Basilica or to the Franciscan Monastery. I suppose in theory either of those could also be accomplished via the cloverleaf, but I just never go that way. It's definitely a much more extravagant interchange than is needed around there.
I can't see the District going along with mrsman's idea to route more traffic via that interchange to eliminate or reduce stopping at the Michigan Avenue traffic light, though, because that might encourage faster speeds on North Capitol and the District is very much looking to slow traffic on most streets.
Quote from: 1995hoo on April 28, 2019, 02:52:47 PM
^^^^
I think I've only passed through that cloverleaf once. Normally if I'm in that area I'll turn right from northbound North Capitol onto Michigan to head to the Basilica or to the Franciscan Monastery. I suppose in theory either of those could also be accomplished via the cloverleaf, but I just never go that way. It's definitely a much more extravagant interchange than is needed around there.
I can't see the District going along with mrsman's idea to route more traffic via that interchange to eliminate or reduce stopping at the Michigan Avenue traffic light, though, because that might encourage faster speeds on North Capitol and the District is very much looking to slow traffic on most streets.
That is certainly true.
DC is particularly insidious with regard to certain speed cameras that are placed on interstate highways (I-395 just before the bridge to VA, I-295 at southern limits of DC). The safety argument for these cameras do not hold water as these are freeways and there are no pedestrians here (but it is fairly lucrative to put a speed camera on a freeway with an artificially low SL of 40 MPH). This section of N Cap also has a speed camera, IIRC.
I think we have to be careful in distinguishing slowing traffic and dealing with congestion. While it is true that congestion will slow traffic, the goal to slow traffic for safety should be to keep traffic moving at a safe speed, not to have everyone stopped because of insufficient capacity. Diverting Mich Ave traffic to Irving will relieve congestion and that is a good thing. N Cap ccan be redesigned to slow down traffic, without having to make everyone stop at Mich Ave.
Either add C/D lanes like at the I-39/90/94/US 151 East Towne interchange in Madison, WI, the I-43/WI 23 Sheboygan interchange in Sheboygan, WI or at most autobahn to autobahn interchanges in Germany, or scrape it all off and replace it from the ground up with free-flow ramps for freeway-to-freeway moves piggybacked over a DDI for a restored cross street, like at the I-39/90/I-43/WI 81/Milwaukee Rd Beloit interchange in Beloit, WI (currently under construction).
IMHO, in nearly all instances where the full cloverleaf connects a freeway to a non-freeway surface road, some form of diamond, folded diamond or par-clo would be massive improvement.
I consider full cloverleaves to be obsolete in most cases.
Mike
Quote from: mgk920 on May 03, 2019, 12:01:38 AM
Either add C/D lanes like at the I-39/90/94/US 151 East Towne interchange in Madison, WI, the I-43/WI 23 Sheboygan interchange in Sheboygan, WI or at most autobahn to autobahn interchanges in Germany, or scrape it all off and replace it from the ground up with free-flow ramps for freeway-to-freeway moves piggybacked over a DDI for a restored cross street, like at the I-39/90/I-43/WI 81/Milwaukee Rd Beloit interchange in Beloit, WI (currently under construction).
IMHO, in nearly all instances where the full cloverleaf connects a freeway to a non-freeway surface road, some form of diamond, folded diamond or par-clo would be massive improvement.
I consider full cloverleaves to be obsolete in most cases.
Mike
Surface to freeway cloverleafs still have the benefit of safety, in addition to capacity and the convenience of not having to stop for signs/traffic lights.
What is the name of the type of ramp where one or more loops/left-turn movements of the cloverleaf is replaced with a lengthy ramp that runs around the interchange? Kind of a sickle-like shape.
One example may be found in Sharonville, OH near Cincinnati, where I-75 meets I-275. This is the ramp that handles the NB->WB movement, presumably the left with the highest traffic volume.
https://www.google.com/maps/@39.2898443,-84.4478413,15.75z (https://www.google.com/maps/@39.2898443,-84.4478413,15.75z)
It's not really a flyover ramp since it tends to be at-grade or on fill as needed, except for when it needs to go over the intersecting roads, twice; there they tend to build ordinary highway overpasses, albeit somewhat banked and curved. The ramp might go under the roads instead one (or both) of those times, depending on the elevations of the respective highways and the topography of the area.
I think you’re referring to a turbine interchange (https://en.m.wikipedia.org/wiki/Interchange_(road)#Turbine_interchange):
(https://upload.wikimedia.org/wikipedia/commons/3/3d/Knooppunt_turbine.png)
I have always liked those interchanges, aesthetically pleasing, functional, and NOT a cloverleaf!
Are there any real life examples of this?
Quote from: mrsman on May 12, 2019, 12:09:14 PM
Are there any real life examples of this?
If you mean turbines, this is the top result: https://www.google.com/maps/@35.3480443,-80.7329325,2023m/data=!3m1!1e3
Quote from: yand on May 12, 2019, 12:53:36 PM
Quote from: mrsman on May 12, 2019, 12:09:14 PM
Are there any real life examples of this?
If you mean turbines, this is the top result: https://www.google.com/maps/@35.3480443,-80.7329325,2023m/data=!3m1!1e3
I noticed that this is the I-485 and I-85 interchange near UNCC. Did this replace the US-29 connector exit from I-85? I panned out from there and I cant find it any more.
Quote from: mrsman on May 12, 2019, 12:09:14 PM
Are there any real life examples of this?
Of a turban/turbine interchange? I use one twice a day. Kellogg @ I-135 here in Wichita.
Quote from: jeffandnicole on April 19, 2019, 03:56:47 PM
Quote from: Amtrakprod on April 19, 2019, 03:24:24 PM
This form is for complaining about cloverleafs and for finding ways to make them better.
iPhone
No traffic lights...free flowing traffic...nothing wrong with them. If they're placed in a high-volume area they will probably fail...but so will many other interchange designs.
I think that they look as beautiful from a birds-eye view as any exit-entrance can look.
Quote from: kphoger on May 13, 2019, 01:51:40 PM
Quote from: mrsman on May 12, 2019, 12:09:14 PM
Are there any real life examples of this?
Of a turban/turbine interchange? I use one twice a day. Kellogg @ I-135 here in Wichita.
Any traffic build up there?
iPhone
Quote from: Amtrakprod on May 23, 2019, 06:44:56 PM
Quote from: kphoger on May 13, 2019, 01:51:40 PM
Quote from: mrsman on May 12, 2019, 12:09:14 PM
Are there any real life examples of this?
Of a turban/turbine interchange? I use one twice a day. Kellogg @ I-135 here in Wichita.
Any traffic build up there?
Generally, the only traffic jams exist because Kellogg is over capacity through downtown, so traffic merging from I-135 to WB Kellogg backs up into the mainline of SB I-135. I encounter this on a daily basis, as it's on my commute route, but I'm going from SB I-135 to EB Kellogg, so I get to take the lane that's pretty much clear.
EB Kellogg occasionally sees some traffic stack up, but generally not major.
I think that cloverleaf interchange was supposed to be part of the I-95 extension that goes through DC.
http://prntscr.com/qjinhi
Quote from: tolbs17 on January 05, 2020, 12:17:24 AM
I think that cloverleaf interchange was supposed to be part of the I-95 extension that goes through DC.
http://prntscr.com/qjinhi
No, I-95 was intended to turn along New York Avenue before turning north again to closely parallel the railroad tracks. It would then turn off and run through where Fort Circle Park is now, with I-270 (then I-70S) continuing along the tracks.
Quote from: kendancy66 on May 12, 2019, 01:38:27 PM
Quote from: yand on May 12, 2019, 12:53:36 PM
Quote from: mrsman on May 12, 2019, 12:09:14 PM
Are there any real life examples of this?
If you mean turbines, this is the top result: https://www.google.com/maps/@35.3480443,-80.7329325,2023m/data=!3m1!1e3
I noticed that this is the I-485 and I-85 interchange near UNCC. Did this replace the US-29 connector exit from I-85? I panned out from there and I cant find it any more.
Yes. I-485 to the southeast was built in the '90s, temporarily feeding into the I-85 trumpet, with the trumpet on US 29 replaced with the existing interchange. The I-85 trumpet was replaced with the turbine when the last segment between I-77 and I-85 opened a few years ago.