Two interchange questions

[XamotCGC]

What are the advantages of a bowtie vs a cloverleaf interchange and vice versa?

What are the advantages of a cloverleaf vs a diamond interchange and vice versa?

[TheStranger]

What are the advantages of a bowtie vs a cloverleaf interchange and vice versa?

What are the advantages of a cloverleaf vs a diamond interchange and vice versa?

For the latter:

- Cloverleaf offers a no-stoplight, theoretically free flow junction.  Can be used for freeway-to-freeway system interchanges.

- Diamond uses less right of way and has no weaving issues, compared to a cloverleaf.

[hbelkins]

There are no advantages to a bowtie unless traffic has to stop, as it did with Kentucky's toll plazas. The short merge areas are a liability, which is why Kentucky is slowly converting the remaining bowties to diamonds (or variants) or parclos.

[cpzilliacus]

- Cloverleaf offers a no-stoplight, theoretically free flow junction.  Can be used for freeway-to-freeway system interchanges.

But when the cloverleaf ramps become overloaded then the two roads
connected by then frequently fail.

That is one reason why at least some state DOT's no longer allow
cloverleaf interchanges, especially at junctions of freeways, freeways
and expressways.

[TheStranger]

- Cloverleaf offers a no-stoplight, theoretically free flow junction.  Can be used for freeway-to-freeway system interchanges.

But when the cloverleaf ramps become overloaded then the two roads
connected by then frequently fail.

That is one reason why at least some state DOT's no longer allow
cloverleaf interchanges, especially at junctions of freeways, freeways
and expressways.

This makes me curious:

With more recent cloverleafs, are the C/D lanes enough to help alleviate some of those issues?

It's telling that California's Department of Highways opted to essentially invent the stack interchange in the late 1940s/early 1950s as an alternative to cloverleaf usage for the Four-Level between 110/101 in downtown LA, though the space-saving aspects of that particular stack have rarely been implemented in many of the others that have been built since.

[skluth]

Bowtie vs cloverleaf

Bowtie

• takes less space than full cloverleaf
• no weaving between cloverleaf ramps and through traffic

Cloverleaf

• no pseudo-roundabouts at end of ramps so often less difficult for trucks
• can be used where two freeways meet

[ran4sh]

- Cloverleaf offers a no-stoplight, theoretically free flow junction.  Can be used for freeway-to-freeway system interchanges.

But when the cloverleaf ramps become overloaded then the two roads
connected by then frequently fail.

That is one reason why at least some state DOT's no longer allow
cloverleaf interchanges, especially at junctions of freeways, freeways
and expressways.

This makes me curious:

With more recent cloverleafs, are the C/D lanes enough to help alleviate some of those issues?

Yes. I would still prefer a semi-directional ramp (as found in a turbine or stack interchange) instead of a loop ramp, but the C/D separates the traffic so that the weaving occurs at an appropriate speed. The space for the C/D lanes also causes the weaving section to be longer, if both routes have C/D lanes.

[Ned Weasel]

There are no advantages to a bowtie unless traffic has to stop, as it did with Kentucky's toll plazas. The short merge areas are a liability, which is why Kentucky is slowly converting the remaining bowties to diamonds (or variants) or parclos.

Bowtie

• takes less space than full cloverleaf
• no weaving between cloverleaf ramps and through traffic

I think we're using two different definitions of "bowtie" here.

[kphoger]

I think we're using two different definitions of "bowtie" here.

I was thinking that earlier, but I wasn't certain, so I didn't post.

Definition 1:  A two-roundabout interchange (or a squished roundabout interchange), such as here

Definition 2:  An doubly-folded diamond interchange (as parclo as a parclo can get?), such as here

[webny99]

Definition 1:  A two-roundabout interchange (or a squished roundabout interchange), such as here

Unless I'm missing something, I think you linked to the wrong location. I don't see any roundabouts there.

[kphoger]

Definition 1:  A two-roundabout interchange (or a squished roundabout interchange), such as here

Unless I'm missing something, I think you linked to the wrong location. I don't see any roundabouts there.

It's a squished roundabout:  1, 2.

If those crossovers were plumped out a bit more, it would be more apparent, but the functionality is the same.

[MCRoads]

Definition 1:  A two-roundabout interchange (or a squished roundabout interchange), such as here

Unless I'm missing something, I think you linked to the wrong location. I don't see any roundabouts there.

It's a squished roundabout:  1, 2.

If those crossovers were plumped out a bit more, it would be more apparent, but the functionality is the same.

Am I correct in saying that is just a grade-separated Michigan Left? Didn't know we needed that...

[webny99]

Definition 1:  A two-roundabout interchange (or a squished roundabout interchange), such as here

Unless I'm missing something, I think you linked to the wrong location. I don't see any roundabouts there.

It's a squished roundabout:  1, 2.

If those crossovers were plumped out a bit more, it would be more apparent, but the functionality is the same.

Oh, I was looking at the wrong road.

You are correct that functionally, it's kind of like half of a squished roundabout. I certainly wouldn't call it a roundabout, though. I'd just call it a U-turn, or, (as just noted) a grade-separated Michigan left.

[kphoger]

Definition 1:  A two-roundabout interchange (or a squished roundabout interchange), such as here

Unless I'm missing something, I think you linked to the wrong location. I don't see any roundabouts there.

It's a squished roundabout:  1, 2.

If those crossovers were plumped out a bit more, it would be more apparent, but the functionality is the same.

Am I correct in saying that is just a grade-separated Michigan Left? Didn't know we needed that...

It's functionally no different than this–just with different yield priorities.

[MCRoads]

Definition 1:  A two-roundabout interchange (or a squished roundabout interchange), such as here

Unless I'm missing something, I think you linked to the wrong location. I don't see any roundabouts there.

It's a squished roundabout:  1, 2.

If those crossovers were plumped out a bit more, it would be more apparent, but the functionality is the same.

Am I correct in saying that is just a grade-separated Michigan Left? Didn't know we needed that...

It's functionally no different than this–just with different yield priorities.

Huh. So it is other a long Dogbone, or a grade separated Michigan Left. That is a very strange overlap.

[kphoger]

Here is a more obvious (but not quite the same) example.