Would you drive on this FLIP-FLOPPED interchange? (It's better in every way!)

America loves "diamond" highway exits. Which is too bad, because when life gets busy, they work pretty terribly. Gil Chlewicki, the "adoptive" father of the Diverging Diamond Interchange (DDI), explains why it's time to untangle our freeway interchanges.


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Sources cited:
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Newspapers:
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"Engineers Chosen For U.S. 19 Work." Tampa Bay Times, March 1, 1974, p. 9B
"Overpass is Simple—If Driver Knows How to Navigate It." Pinellas Times, January 13, 1974, pp. 1,3
"Growing a Bridge in American Fork." Provo Daily Herald, August 21, 2009, p. C1
"New Interchanges May Ease I-15 Congestion." The Salt Lake Tribune, May 21, 1993, p. D1
"First in U.S. 'diverging diamond' highway interchange." Springfield News-Leader, May 29, 2008, p. 1B
"Diverging diamond has residents excited." Springfield News-Leader, January 14, 2009
Photo, Ozarks News-Leader, July 2, 2008, p. 11
"Interchange will diverge from norm." Springfield News-Leader, June 25, 2008, p. 1

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Time sections:
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Introduction: (0:00)
Diamond Love: (1:01)
Gil Goes to France: (2:42)
SPUIs: (4:59)
How DDIs Work: (6:54)
Gaining Acceptance: (9:58)
America's First DDIs: (12:19)
Lessons Learned: (14:51)
What About Pedestrians?: (20:04)

[PracticalEngineeringChannel]

Well, I'm taking this topic off my list of video ideas ;) Couldn't have been done better. Awesome video.

[TrainfanJanathan]

I remember the first time I saw one of these as a truck driver. I asked my trainer, "so am I supposed to drive on the left side?"

[startreking]

My town got one, it removed horribly programmed lights. I love that.

[shaggyfilms]

My mom thought I was autistic when i was a child because i was obsessed with roads and road signs. I still am today and i feel like I have finally found my people. Thanks Rob

[WhyBeNick]

I live in Springfield MO where we got the first one in the US. People whined and cried about it during construction, but quickly realized that these things are amazing. We now have several of them throughout the city.

[MicahPotts]

4:58 if you have ClosedCaptions on it describes the music as "Inexpensive, but surprisingly good, disco stock music" lol. Props to whoever put that together!

[brianloper]

Yes, now we need more roundabouts. I'm tired of stopping at 4way stop signs from 10pm-5am in rural/suburban areas when nobody is there

[RowanHawkins]

The one in Rochester was the first one in NY. It has a high center wall under the bridge and frankly helps enforce traffic exiting the interstate it ends before the cross point so it doesn't block vision there. It also helps with idiots leaving their high beams on coming off the unlit 3digit interstate onto a lit city street.

[ebob]

I think the reason people are not turning left on red is that the signal is a red arrow. Around here, that usually means that you cannot make an unprotected left turn. I think it would work better with a solid red (not arrow) and a flashing yellow arrow.

[vizender]

19:48. At this situation, as a French guy, I’ll just make the two intersections roundabouts. The freeway exit is always the busiest, so the roads from the DDI are also the busiest, and roundabouts are great at dealing with this kind of imbalanced traffic, and it seems there is enough room to put 3 lanes roundabouts at least

[mjrc]

This channel is still so massively underrated.

[Arjay]

I actually really like these, they are very simple, just follow the arrows/lanes, they are safer and from a Cities Skylines player perspective I love that they are "small".

[custardo]

A choice quote from the UDOT report: "There are no viable transportation alternatives to cars for residents of
West Lehi, Saratoga Springs, or Eagle Mountain." Well done Utah, well done.

[mabus]

I live in Indiana... and suprisingly they have a few of these intersections at junctions with I-69. Also, lots of roundabouts.

[think-forge]

The production and the jokes are next-level! On a more serious note, when do you plan on releasing a review on the Mitsubishi Mirage?

[JP-subp]

The first time I saw one of these was when I exited for fuel. My first thought was, "Who thought up this crazy {insert bad word here}?"

While filling my fuel tank, I watched vehicles travel through the intersection and noticed how few had to stop.

By the time I'd replaced my fuel cap, I was thinking, "Who thought up this brilliant {insert bad word here}?"

[krisswolf]

“Left on red after stop” problem can be solved by just making the red arrow blink instead of a solid red

[petuniasevan]

They put in a DD intersection in Appleton Wisconsin recently; it's at highway 441 on Oneida Street. I was suspicious of it at first as to its ability to control traffic as advertised (unlike all the interchange embedded traffic circles around here that are poorly designed) but the DDI setup is working so far.
Great video, Rob; I didn't even know what the nomenclature was for this setup before I watched this.

[bradybirdy]

It's so cool watching your videos as a SLC local, I worked as a driver for a couple of years and spent a lot of time traveling back and forth through the valley. Spent a lot of time thinking about how these roads work, so seeing your detailed explanations while using those same very roads as examples is really awesome! Thanks for the great content man, keep it up!

[TheBenghaziRabbit]

we have one of those here and at first it had me feeling uneasy but you get used to it.