Diverging Diamonds: Still Not the Pedestrian's Best Friend
Every good story needs a villain. I’ve been happy to be that villain for the Diverging Diamond Interchange since I first wrote about it, and produced a video narration, back in 2011.
What began as commentary on the engineering profession has evolved into a psychological experiment, of sorts. Every now and then the video gets pounded with taunting comments from people asserting how idiotic I am because science and data has now shown that the diverging diamond works.
Here’s the latest:
How do you have the courage to keep this video online after the now proven success of this concept?
-Carlos Zorro
LMAO bet you feel like a real dumbass b*tch now. Go back to engineering children's toys you @@cking brainlet
-Ed Krassenstein
The guy making this video seems to be a complete idiot with a preconceived agenda.
-Justin Murtagh
What has turned into psychology for me is how people hear one thing, impose a completely different narrative, then taunt me with their narrative. Anyone who listens to the video is immediately confronted with my core critique. This comes from the first 35 seconds of the video:
I was given this video of this very enthusiastic engineer narrating this diverging diamond interchange and how it was so pedestrian friendly. I was asked to comment on it so I thought I would narrate my comments as we go to explain why this is an apostasy when it comes to pedestrians and pedestrian traffic.
My critique is and always has been that these are not “pedestrian-friendly” as the industry likes to claim. There is nothing about them that is kind and pleasant (the definition of friendly) for humans outside of an automobile. Note that nowhere do I say it won’t work for traffic. In fact, in another article on this topic (there are many), I’ve written the following:
The DDI is a brilliant design if your goal is to improve traffic flow without increasing the width of the interchange. It will handle more vehicles-per-hour, especially during peak times, and it will do so with improvements to traffic safety. It can also be engineered to accommodate pedestrians in ways that are safer than non-DDI interchanges.
All of this is true, and I’ve never argued that it wasn’t.
The fact that I have to keep saying this demonstrates over and over how myopic engineers and auto-enthusiasts can be. If I went to order a pizza with a traffic engineer, here’s how I think the conversation would unfold, given all I’ve experienced:
Traffic Engineer: We’re going to have a pizza that is going to be absolutely amazing for vegetarians.
[Traffic Engineer orders a Meat Lovers pizza with a side salad.]
Traffic Engineer: I told you this pizza was going to be awesome for vegetarians.
Me: This pizza sucks for vegetarians. It’s the exact opposite of a pizza a vegetarian would want.
Traffic Engineer (talking to me while looking over at a group of fellow engineers): Wow, you’re such an idiot. This pizza is going to taste great. Don’t you feel dumb.
The latest in this genre of ignorance comes from YouTuber Austin McConnell who apparently does informational videos in a garage band version of Adam Ruins Everything. He did one on diverging diamonds which was okay until it got to the 6:30 mark. Here’s how it went at that point:
When the Diverging Diamond Interchange was first proposed in America it got a lot of flack from this guy: Charles Marohn, a recovering engineer, whose major complaint was that the design was ugly, unfriendly to pedestrians, and likely that it looked so wonky that more accidents would be caused by people who didn’t understand it and how it worked than anything.
In fact, he made this cutthroat video lambasting the design in 2011, practically forecasting its utter failure. Well, it’s been seven years and rather than spawning the interchange apocalypse, it turns out injury accidents at these locations have seen a 60% drop.
My complaints apparently were that it was (1) ugly, (2) unfriendly to pedestrians, and (3) it would cause more accidents due to confusion. I ‘“practically forecasted its utter failure”. This is absurd, and the fact that the video has 3.5 million hits does nothing to attest to the accuracy or thoroughness of Mr. McConnell.
Diverging diamond in Springfield, Missouri. Image source.
And note McConnell’s casual use of language. He says I “likely” thought it looked so wonky it would cause accidents and I “practically” forecast its failure. He’s making stuff up having not done any research on what I actually said. It’s not like I’m difficult to get a hold of, but he never contacted me or apparently even read any of the numerous articles I’ve written on the topic.
Again, the original traffic engineer claimed the decorative brick and the view of traffic was “beautiful” for people walking. Follow those links and listen to him—the dissonance with reality is astounding. The traffic engineer also pointed out that a driver was confused, and even cited it was the presence of a pedestrian that was disorienting, and I agreed with that because that’s what his video showed. His claim was that the DDI is pedestrian friendly. Watching his video, that claim is clearly not true, and I stand by that analysis, no matter what traffic counts are.
Traffic engineers can say their meat lovers pizza will be loved by vegetarians because they also ordered a side salad, and people like McConnell can mindlessly parrot those assertions, but not a single person has ever—EVER—provided even the feeblest rebuttal to my argument that this diverging diamond interchange is a terrible environment for humans outside of a vehicle.
Cover image: Diverging diamond interchange in Springfield, Missouri. Image source.
Charles Marohn (known as “Chuck” to friends and colleagues) is the founder and president of Strong Towns and the bestselling author of “Escaping the Housing Trap: The Strong Towns Response to the Housing Crisis.” With decades of experience as a land use planner and civil engineer, Marohn is on a mission to help cities and towns become stronger and more prosperous. He spreads the Strong Towns message through in-person presentations, the Strong Towns Podcast, and his books and articles. In recognition of his efforts and impact, Planetizen named him one of the 15 Most Influential Urbanists of all time in 2017 and 2023.