The Diverging Diamond Interchange Looks Like Hell But Promises a Safer Future

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Screenshot: Florida DOT

What you’re looking at is what’s known as a diverging diamond interchange, an emerging concept in highway design that aims to eliminate the left turn and thereby increase safety, even if, from the top down, it looks like complete chaos.


The concept isn’t new, exactly, having been first proposed by an engineering student in the early aughts, but, in the U.S. they have begun to proliferate, with over 100 operating in multiple states. The largest of these is in Florida, where, last year, officials completed a diverging diamond interchange on University Parkway on the Manatee and Sarasota county line that at its widest constitutes 12 lanes of traffic. (A map of diverging diamond interchanges across the world can be found here.)

The concept is pretty simple: Fewer stops for drivers, and a total elimination of left-hand turns into oncoming traffic. Here is a soothing video from the Florida Department of Transportation showing how it works:

I drove through a (much smaller) diverging diamond recently in Springfield, Missouri, which built the first diverging diamond in the country in 2009, and I can report that the experience was jarring at first, but after a few times through, it became familiar, even if it wasn’t immediately evident what the point of it all was.

Researchers, though, have said the point is clear, with studies showing that diverging diamond interchanges reduce instances of fatal crashes by over 60 percent, and total crashes by around 33 percent. They can also be built to accommodate bike lanes and pedestrian walkways, as this video shows.

How’s it going at the largest in Florida? Pretty well, according to a post on the website for America’s Transportation Awards, an organization sponsored in part by AAA and the U.S. Chamber of Commerce.

Since opening, commuters using this interchange have experienced a 40 percent reduction in travel delays, a reduction in vehicular crashes up to 50 percent by decreasing the number of conflict points, and enhanced mobility.

Mainly, to my eye, diverging diamond interchanges show that the left-hand turn against opposing traffic is increasingly on its way out. UPS truck drivers, for example, have been banned from them for years, a move which the company has said has reduced accidents, reduced the length of driver routes, and increased efficiency.

Correction, 3:41 p.m.: The lede has been amended to say that this type of interchange increases safety, not reduces it, which, uh, I think was probably leftover from a longer sentence about reducing accidents and increasing safety but that doesn’t excuse error. Apologies!


Correction, Friday 1:41 p.m.: Missouri built the country’s first diverging diamond interchange in 2009, not 2014 as I originally wrote. I’m a dumbass.



It looks great in concept, but I can tell you in MA, this would be pure chaos.

This design appears to rely heavily on the painted lines in the roads. I can’t even tell you the last time I saw a straight painted line on one of our major roadways here. The state seems to have it as a criteria for whoever they source the job to. I can only assume that part of the bidding process involves giving the foreman a coloring book and the one who looks the closest to a 2 year old’s skill level gets the job.

Edit: And that is assuming the line is even there. Most of them have long since faded away.