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.
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.
FULL STORY: The Diverging Diamond Interchange Is Coming to a Road Near You
How I Learned to Stop Worrying and Love the Roundabout
What drives the U.S. backlash to roundabouts — objectively safer and more efficient than stop-and-go intersections?
How Well Will San Francisco’s Daylighting Program Work?
Unlike other efforts to prevent cars from parking near intersections to improve visibility and road safety, San Francisco has no plans to install physical infrastructure to keep vehicles out of danger zones.
San Francisco Officials Call for Citywide Ban on Right Turns on Red
A proposal to prohibit turns on red at some downtown intersections prompted calls for a blanket ban for the entire city.
Rethinking Redlining
For decades we have blamed 100-year-old maps for the patterns of spatial racial inequity that persist in American cities today. An esteemed researcher says: we’ve got it all wrong.
Planetizen Federal Action Tracker
A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.
California High-Speed Rail's Plan to Right Itself
The railroad's new CEO thinks he can get the project back on track. The stars will need to align this summer.
San Francisco Muni Raises Fares a Second Time
A 10–cent fare hike for adults is part of the agency’s plan to chip away at a growing budget deficit.
Electric Grid Capacity Could Hamstring EV Growth
Industry leaders say the U.S. electric grid is unprepared for the increased demand for power created by electric cars, data centers, and electric homes.
Texas Bill Supports Adaptive Reuse in Commercial Areas
Senate Bill 840, which was preliminarily approved by the state House, would allow residential construction in areas previously zoned for offices and commercial uses.
Urban Design for Planners 1: Software Tools
This six-course series explores essential urban design concepts using open source software and equips planners with the tools they need to participate fully in the urban design process.
Planning for Universal Design
Learn the tools for implementing Universal Design in planning regulations.
City of Camden Redevelopment Agency
City of Astoria
Transportation Research & Education Center (TREC) at Portland State University
Regional Transportation Commission of Southern Nevada
Toledo-Lucas County Plan Commissions