May 16, 2017


Diamond-Shaped Intersections Prevent Crashes by Cutting Out Left Turns (MICHELE DEBCZAK,  JUNE 6, 2016, Mental Floss)

The "diverging diamond interchange" (or DDI) replaces the traditional layout of an intersection with a clever design that's more efficient and less likely to lead to accidents. It works like this: At the intersection, two roadways carrying opposing traffic temporarily swap sides, creating a diamond shape. At the points where the roads intersect, traffic lights regulate who crosses when. (For a better idea of how they function in real life, you can check out the video below from the Florida Department of Transportation.)

The biggest difference with the design is that drivers turning left no longer have to pull out in front of oncoming traffic to do so. They can easily turn onto the diverging left lane when driving on the opposite side of the road.

The concept gained popularity in the U.S. after a grad student named Gilbert Chlewicki wrote a term paper detailing it. Even after discovering that the French had been using his idea since the 1970s, he continued to promote it here in the States. Today there are 62 DDIs in 22 states, and their effectiveness indicates that they're here to stay.

Posted by at May 16, 2017 5:57 AM