Is that a DDI? Oh My!

0 By phw_admin Sep 03, 2014

Diverging-diamond (or double crossover diamond) interchanges (DDI) are like a remix of the traditional diamond interchange found at the intersection of interstates and highways. The first thing one will notice about the DDI is that traffic is routed to the left side of the road as it enters the DDI. Then as traffic leaves the DDI, it is routed back to the right side of the road. By moving the traffic to the left side of the DDI cars can make a “free” left turn onto the interstate. This turn is considered “free” because left-turning cars will not have stop or cross in front oncoming traffic once they enter the DDI. Right turns onto the interstate are still free as well because those cars can peel off to the right before entering the DDI. Because of these two free turning movements, DDIs allow traffic to move through the interchange more efficiently and quicker than through a traditional interchange.  Less stop time and more go time also reduces vehicle emissions by reducing idle time.

The DDI is safer than a traditional interchange; it has almost half as many conflict points as a traditional interchange.  A conflict point is commonly used to explain the accident potential of a roadway, or a point where two vehicles can cross, merge, diverge, etc. The DDI, by design, nearly eliminates wrong way entry to ramps onto the interstate and shortens the distance pedestrians have to cross in front of vehicles.

Watch how traffic moves through the DDI in the videos below. We’ve also posted some additional links and videos about the DDI at the bottom of the page.

For more information about DDI’s, watch the below videos:

https://www.youtube.com/watch?v=eLAwwl3EtN4
https://www.youtube.com/watch?v=_L-8z7v1VEc

Note: The videos above are for informational purposes only and not related to the Pete’s Highway project.

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