Best Interchange Designs

[skluth]

I always liked driving through this interchange on I-395 at Shirlington, though I'm sure the anti-roundabout crowd would hate it.

I also like this interchange in my original hometown of Green Bay because it feels rural even though it's on the edge of the city. It has a couple left entrances, but I've never found them a problem.

[johndoe]

I have always liked I-395 and King Street in Alexandria, Virginia, because of how it nicely and cleanly eliminates the weave-area problem that is a central issue with a standard cloverleaf. Yes, it requires two additional overpasses, but overall those are a minor addition when compared to flyover ramps or similar.
(snip)

Very similar design is used where MD-43 intersects I-95 north of Baltimore, except the "loop ramps" also allow for left hand turns to facilitate left turns at cross streets near the intersection.

Whoa. The left turn from the loop is a really interesting concept. For those who are curious, start here.

That is interesting.  On the one hand, is that left turn continuous T really worth extra bridge area when they're headed for a signal anyway?  A two-phase signal was fine on the other off-ramp.  But on the other hand, I guess the "westbound to southbound" requires a bridge there anyway.

I've always been confused why agencies gravitate towards Parclo A4s. 

Just guesses, but I suspect sometimes things are popular because they're popular.  (like your previous comments about DDI)  Maybe they're not the best choice but they're the familiar choice.  My other guess is that agencies worry more about vehicles losing control at lower speed off-ramps.  From what I've heard working in the industry, there are more problem cases decelerating on a loop ramp (including more serious crashes like rollovers) than accelerating.

For some reason I pictured "A4" and "B4" as "after" and "before", but it's the opposite: "ahead" and "behind".

IMO it's still easiest to remember them as "accelerate" or "brake".

[interstatefan990]

The lone diverging diamond interchange in Florida and also the largest one in the country, I-75 and University Parkway. I've driven through there many times for business, and once they converted it from the old design, traffic flow overall was a lot faster and smoother. A lot of people didn't like it at first, but once I got used to it I quickly appreciated its improvements and benefits.

[SkyPesos]

The lone diverging diamond interchange in Florida and also the largest one in the country, I-75 and University Parkway. I've driven through there many times for business, and once they converted it from the old design, traffic flow overall was a lot faster and smoother. A lot of people didn't like it at first, but once I got used to it I quickly appreciated its improvements and benefits.

Holy that's a wide cross road. 12 lanes under the bridge, with 5 through lanes per direction?

[MCRoads]

The lone diverging diamond interchange in Florida and also the largest one in the country, I-75 and University Parkway. I've driven through there many times for business, and once they converted it from the old design, traffic flow overall was a lot faster and smoother. A lot of people didn't like it at first, but once I got used to it I quickly appreciated its improvements and benefits.

Holy that's a wide cross road. 12 lanes under the bridge, with 5 through lanes per direction?

There are at least 5 DDIs in FL now...

[interstatefan990]

The lone diverging diamond interchange in Florida and also the largest one in the country, I-75 and University Parkway. I've driven through there many times for business, and once they converted it from the old design, traffic flow overall was a lot faster and smoother. A lot of people didn't like it at first, but once I got used to it I quickly appreciated its improvements and benefits.

Holy that's a wide cross road. 12 lanes under the bridge, with 5 through lanes per direction?

There are at least 5 DDIs in FL now...

Whoops. I meant to say that when it opened, it was the lone DDI open to traffic in Florida. My bad!

Holy that's a wide cross road. 12 lanes under the bridge, with 5 through lanes per direction?

It really is. Reminds me of Texas-style urban freeway design, which is to make everything as wide as possible. I wonder if there is a world record for the difference in the number of lanes between a freeway and the cross road that it over(under)passes. In this case it is 6 lanes, with I-75 being 6 and University Parkway being 12.

[tolbs17]

I'm a huge fan of Parclos. Separated!

[ran4sh]

It really is. Reminds me of Texas-style urban freeway design, which is to make everything as wide as possible. I wonder if there is a world record for the difference in the number of lanes between a freeway and the cross road that it over(under)passes. In this case it is 6 lanes, with I-75 being 6 and University Parkway being 12.

If a freeway crosses over/under an intersection of 2 roads, do both of those lane counts count? For example, a 14-lane freeway going under an intersection of a 4-lane street and a 3-lane street, for a total of 21. https://goo.gl/maps/whVS45ST85z71KV4A (Or if you count lanes of ramps, you can look at the intersection one block to the southeast)

[WillWeaverRVA]

I particularly like the VA 168 BUSINESS/Greenbrier Parkway/I-64 interchange complex in Chesapeake, Virginia. Yes, it's two cloverleaf interchanges, but it's the braided ramps that do it for me.

https://www.google.com/maps/@36.7793724,-76.2417933,2532m/data=!3m1!1e3

[interstatefan990]

It really is. Reminds me of Texas-style urban freeway design, which is to make everything as wide as possible. I wonder if there is a world record for the difference in the number of lanes between a freeway and the cross road that it over(under)passes. In this case it is 6 lanes, with I-75 being 6 and University Parkway being 12.

If a freeway crosses over/under an intersection of 2 roads, do both of those lane counts count? For example, a 14-lane freeway going under an intersection of a 4-lane street and a 3-lane street, for a total of 21. https://goo.gl/maps/whVS45ST85z71KV4A (Or if you count lanes of ramps, you can look at the intersection one block to the southeast)

I guess it would not count since they are separate roads. One large road going under/over a freeway is more impressive than two smaller roads going under/over, at least in my opinion.