Videos

The 'Diverging Diamond' Interchange Is an Abomination

A "recovering" engineer tears apart the latest "complete streets" design trend

Charles Marohn is an engineer who is outraged by engineers. Marohn runs Strong Towns, a nonprofit organization in his home state of Minnesota that advocates less dependence on the building of new infrastructure as a model of economic development, and greater focus on getting more out of the infrastructure we already have.

Marohn has written a lot about bad road design -- his “Confessions of a Recovering Engineer” is a classic. Now he's come out with a video critique of the “diverging diamond” design that's gaining traction among engineers tasked with creating “complete streets” (streets that cater to all users, pedestrians, bicycles, and cars). The diverging diamond is a design that moves cars quickly across a freeway without building an expensive cloverleaf exchange, while at the same time providing accommodation to non-car transport.

This particular diverging diamond is in Springfield, Mo., and in the video an engineer gives us a proud tour of all its supposedly pedestrian- and bike-friendly features. Only problem is, this looks like an exhaust-choked wasteland where no one would ever walk unless they were absolutely desperate, maybe even destitute.

“The first thing that came to my mind was the Star Wars Death Star scene," says Marohn of when he first watched the video. "I thought, this needs some Death Star music, so I started there.” So you’ll see some Luke and Darth action.

You’ll also get Marohn’s point-by-point gobsmacked rebuttal to the 10-minute tour. When the man on the video says, “This wonderful, beautiful, red ornate treatment on the brick [gives] it a nice decorative look,” Marohn replies, “The craziest thing is that somebody spent a ton of money on red decorative brick. Why? So that cars can feel better about themselves when they drive by? This is insanity.”

The way Marohn sees it, talking about the diverging diamond as if it creates a street that is truly useful and welcoming to pedestrians and cyclists is, at its heart, propaganda that willfully ignores the truth on the ground. Once engineers have checked off the boxes required by the design code, they can convince themselves that they have made a “complete street.”

"The engineering profession has devolved,” says Marohn. “It’s just, ‘Do I meet the criteria?’ This stuff looks good from the air, it looks good on a set of plans. It even looks good when you drive by. But we’re not exactly building a place here that is going to add any value to society.“

Of the original video's narrator, Marohn says, “He’s probably a fine person, I’m not trying to attack him personally. But it’s almost like the Central Committee sent him out there. It could have been Pravda putting this together.” He pauses, as if trying to find something nice to say. "To be generous, this is so 1950s."

About the Author

  • Sarah Goodyear has written about cities for a variety of publications, including Grist and Streetsblog. She lives in Brooklyn.