New Type of Interchange

[kernals12]

Some Eastern European engineers have come up with a new type of interchange that's gotten a small amount of media attention. They call it the inside turning left interchange and involves having the main carriageways split apart creating an open square where the left turn ramps go.

They make great claims, saying that it can handle more traffic than even stack interchanges while requiring fewer grade separated bridges than any interchange design besides the cloverleaf making it less expensive. What do you guys think about it?

[Revive 755]

^ Looks somewhat similar to I-70 at I-170 in the St. Louis area but requiring more ROW. It would also have problems with left side exits, which a stack does not.

Maybe the eastern I-80/I-35/I-235 interchange in Des Moines prior to the last major modification (which put in the lanes going straight through between I-35 and I-235) would be a better comparison for how wide the median would have to get

[kernals12]

^ Looks somewhat similar to I-70 at I-170 in the St. Louis area but requiring more ROW. It would also have problems with left side exits, which a stack does not.

Maybe the eastern I-80/I-35/I-235 interchange in Des Moines prior to the last major modification (which put in the lanes going straight through between I-35 and I-235) would be a better comparison for how wide the median would have to get

There's a similar interchange between CT 9 and I-91 .

They have videos showing how such an interchange could fit in the existing area of current conventional interchanges. They claim it uses no more space than a cloverleaf and less space than a turbine.

[vdeane]

I-390/NY 390 and I-490 also does this.

[kernals12]

I-390/NY 390 and I-490 also does this.

I think this may be like the Diverging Diamond Interchange. Someone in one part of the world thinks up one type of interchange without knowing that that design has already been implemented unceremoniously in another part of the world.

[jeffandnicole]

Numerous issues:

Left exits are generally not favored.

At least in this example, there are only two thru lanes thru the interchange on each carriageway. Reducing throughput by even one lane generally creates congestion. Here, it's reduced by 2 lanes, which greatly reduces capacity, not increase it.

Also in this example, there is a significant amount of overpasses. Overpasses are extremely costly. For the most part the overpasses can be eliminated in favor of embankment, but even then there's still a need for 8 separate overpasses.

There are S curves approaching and leaving the interchange area. Whenever possible, it's better to place interchanges and the accel/decel lanes on straightaways.

[kernals12]

Numerous issues:

Left exits are generally not favored.

At least in this example, there are only two thru lanes thru the interchange on each carriageway. Reducing throughput by even one lane generally creates congestion. Here, it's reduced by 2 lanes, which greatly reduces capacity, not increase it.

Also in this example, there is a significant amount of overpasses. Overpasses are extremely costly. For the most part the overpasses can be eliminated in favor of embankment, but even then there's still a need for 8 separate overpasses.

There are S curves approaching and leaving the interchange area. Whenever possible, it's better to place interchanges and the accel/decel lanes on straightaways.

That's supposed to be one of the great advantages. It requires fewer overpasses than a comparable stack or turbine interchange.

[skluth]

This is the old Zoo Interchange in Milwaukee. It's quite similar with left on and off ramps in all directions. It was named for the nearby zoo, not because it was terrible with lots of weaving and accidents causing backups on both freeways with drivers turning into animals. They rebuilt it a few years back into an interchange that worked. Let's not repeat the mistakes of the past with an alleged new idea, like politicians or fashion designers.

[froggie]

It's not new.  It's effectively a directional interchange...

[kernals12]

It's not new.  It's effectively a directional interchange...

But it has much shorter left turn ramps.

[jeffandnicole]

Numerous issues:

Left exits are generally not favored.

At least in this example, there are only two thru lanes thru the interchange on each carriageway. Reducing throughput by even one lane generally creates congestion. Here, it's reduced by 2 lanes, which greatly reduces capacity, not increase it.

Also in this example, there is a significant amount of overpasses. Overpasses are extremely costly. For the most part the overpasses can be eliminated in favor of embankment, but even then there's still a need for 8 separate overpasses.

There are S curves approaching and leaving the interchange area. Whenever possible, it's better to place interchanges and the accel/decel lanes on straightaways.

That's supposed to be one of the great advantages. It requires fewer overpasses than a comparable stack or turbine interchange.

But more than a cloverleaf.

[froggie]

It's not new.  It's effectively a directional interchange...

But it has much shorter left turn ramps.

Doesn't matter.  Fundamental design is still the same..."left-turning movements" have ramps on the left.

[hotdogPi]

Four overpasses: M25 at A1(M), also M25 at M20 if you ignore the minor roads

[kernals12]

This is the old Zoo Interchange in Milwaukee. It's quite similar with left on and off ramps in all directions. It was named for the nearby zoo, not because it was terrible with lots of weaving and accidents causing backups on both freeways with drivers turning into animals. They rebuilt it a few years back into an interchange that worked. Let's not repeat the mistakes of the past with an alleged new idea, like politicians or fashion designers.

I don't see where the weaving would occur

[sprjus4]

The junction between I-26 and I-40 outside Asheville, NC is similar, though has a couple missing movements due to proximity to other connections.

https://www.google.com/maps/@35.5544399,-82.6066082,1881m/data=!3m1!1e3!5m1!1e1?hl=en

[cpzilliacus]

Junction of I-95 at MD-32 (Patuxent Freeway) in Columbia, Howard County, Maryland has some similarities.  Google Maps here. 

The point at which the left-side ramp from eastbound MD-32 to northbound I-95 merges on the left is problematic (I have seen several crashes here over the years).

The cloverleaf ramp from northbound I-95 to westbound MD-32 is quite sharp, (signed for 30 MPH) and there have been truck mishaps on that ramp more than once.

[DJStephens]

This is the old Zoo Interchange in Milwaukee. It's quite similar with left on and off ramps in all directions. It was named for the nearby zoo, not because it was terrible with lots of weaving and accidents causing backups on both freeways with drivers turning into animals. They rebuilt it a few years back into an interchange that worked. Let's not repeat the mistakes of the past with an alleged new idea, like politicians or fashion designers.

   The old Albuquerque Interchange of I-25 and 40 was built quite like this old Zoo interchange as well.  Built in the mid sixties, it became overloaded within two decades.  Lack of a Beltway meant all longer distance traffic needed to go through it, and it was under-built to begin with.   
   Exiting means one had to move over to the fast lane to exit, and then one enters the fast lane upon reaching their chosen route.  Not good design.   
   Not sure why Connecticut adopted the left hand exit/entrance mode to the extent that they did.   

[skluth]

This is the old Zoo Interchange in Milwaukee. It's quite similar with left on and off ramps in all directions. It was named for the nearby zoo, not because it was terrible with lots of weaving and accidents causing backups on both freeways with drivers turning into animals. They rebuilt it a few years back into an interchange that worked. Let's not repeat the mistakes of the past with an alleged new idea, like politicians or fashion designers.

I don't see where the weaving would occur

It's the same problem as every other highway with left entrance/exit ramps compounded by the nearby interchanges within a mile in all four directions. There was a lot of traffic using the left entrance/exit ramps in combination with using those next interchanges. Others would be surprised by the left exits and rapidly cross to make their exits. Many were visitors going to the zoo, the state fairgrounds, and the nearby hospitals and unfamiliar with the area. I believe it was either the busiest or second-busiest (after the Marquette Interchange at I-43/I-94 downtown) interchange in Wisconsin. I know my relatives in Oak Creek and Waukesha hated it.

[paulthemapguy]

Either this interchange would need to be really expansive, or the grades on the inner ramps would need to be colossally steep.

[MCRoads]

I-390/NY 390 and I-490 also does this.

I think this may be like the Diverging Diamond Interchange. Someone in one part of the world thinks up one type of interchange without knowing that that design has already been implemented unceremoniously in another part of the world.

Except there is one small difference: the DDI was actually a good idea. This design has already been built numerous times, and almost all of them were replaced by interchanges that actually work. It is almost funny how bad this design is!

[GaryV]

A similar interchange at I-96 and US-23 was rebuilt.  I don't recall if the old one had left exits/entrances for all 4 directions, but it had several.  The median of I-96 was so wide that there were houses in it.

[kphoger]

It's not new.  It's effectively a directional interchange...

Quoted for emphasis.

All they did was spread the mainline lanes apart instead of keeping them together.  Other than that, it's the same beast.

[sprjus4]

Another close one - I-37 / US-281 / I-35 junction in San Antonio, TX

https://www.google.com/maps/@29.4391138,-98.4786416,923m/data=!3m1!1e3!5m1!1e1

Has a few left exits and entrances, particularly due to I-37 / US-281 splitting, though has a few semi-directional ramps.

[MCRoads]

It's not new.  It's effectively a directional interchange...

Quoted for emphasis.

All they did was spread the mainline lanes apart instead of keeping them together.  Other than that, it's the same beast.

My mom hated that interchange with a passion . Going from NB I-44 to WB I-44 was especially harrowing, as the mainline traffic was going 65-70, but ramp traffic is going around 40-45.

But my mom's absolutely most hated interchange was the I-35 and I-240. I don't blame her. The loop ramps are tiny, and I-240 traffic did not give 2 craps about people merging onto the freeway. Hell, I wasn't driving, and I was always afraid we would get rear-ended by a butthole exiting SB I-35 at 65. Thank god they are redoing that interchange, I won't miss it.

[BrianP]

The interchange that came to mind for me is I-70/77 in Ohio which also does half of this proposal.  And looking at that existing interchange makes me believe that you would have to separate the carriageways by a significant amount more than that existing interchange to fit the ramps in the middle. Perhaps as much as doubling the distance between the carriageways would be necessary.  The image above looks nice but I think it's deceiving about the size of such an interchange.  I think it's just too big to actually make it worth while without even getting to the left exit issue. 

Also take into account that the advisory speed for one of the left exit ramps in the interchange I mentioned is only 45 mph.