The diverging diamond interchange (DDI) is an interchange form that allows two directions of traffic on the crossroad to temporarily divide and cross to the opposite side to gain access to and from the freeway easily. The difference between a DDI and a conventional interchange is the design of directional crossovers on either side of the interchange. This eliminates the need for vehicles turning left to cross the path of approaching vehicles.

Diverging Diamond Interchange (DDI) illustration

Illustration: Diverging Diamond Interchange (DDI)


Diverging Diamond Interchange (DDI) photo

Photograph: Diverging Diamond Interchange (DDI)

A. Directional crossover for through movements functions as a two-phase signal.

B. Right turns typically yield to lefts on on-ramp.

C. Left-turn movements.