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On the Rise of the Diverging Diamond Interchange

Its design can appear baffling at first, but the DDI presents drivers with far fewer opportunities to collide with each other than traditional four-way intersections.
September 18, 2017, 9am PDT | Philip Rojc | @PhilipRojc
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Laura Bliss covers the spread of the diverging diamond interchange, or DDI. "Rather [than] make drivers turn at a right angle to merge onto a highway, the two directions of traffic diverge and ribbon over one another. One lane peels off to funnel cars onto the highway, and they never have to turn against traffic."

Bliss includes an embedded Youtube video from the city of Calgary, which cheerily explains how drivers should use a DDI.

"DDIs are proliferating because they're safer than a traditional four-way intersection. Where two, two-lane roadways intersect, drivers have 32 separate opportunities to collide into each other. In a DDI, there are only 14." They can also incorporate pedestrian crossings, as the Calgary video shows. 

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Published on Monday, August 21, 2017 in CityLab
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