User:TerryPurdue/Junction Style Guide/Interchanges

Diverging Diamond Interchange (DDI)

See also: Diverging Diamond Interchange article on Wikipedia.

Diverging diamond interchanges (DDI) are a type of diamond interchange in which the two directions of traffic cross to the opposite side as they pass over/under the limited-access roadway.

This type of interchange is unusual, in that it requires traffic to briefly drive on the opposite side of the road from what is customary for the jurisdiction.

At-Grade Intersections

(TODO: add zoomed in pic of one of the at-grade intersections)

All DDI's contain exactly 12 at-grade intersections:

• Two "outer surface road" intersections, where drivers on the surface road enter/exit the DDI
• Two "inner surface road" intersections, where the two directions of travel along the surface road "cross over" each other at signaled intersections.
• Four "offramp" intersections, where drivers use ramps to exit the limited-access road and enter the DDI
• Four "onramp" intersections, where drivers transition from the surface road segments inside the DDI onto ramps that lead to the limited-access road