Diverging Diamond Interchange
What is a DDI?
A DDI, short for Diverging Diamond Interchange, is a French engineering concept in which the two directions of traffic are crossed to the opposite side to provide easier access on and off the freeway. This reduces the number of traffic signal phases needed to move motorists through the interchange to two, as opposed to the usual three or four. DDIs efficiently move high volumes of traffic without increasing the number of lanes in an interchange.
How safe is a DDI?
Safety was a critical factor that was used in analyzing the viability of the DDI. Our studies show that because traffic crosses from the right side of the road to the left side, movements onto the freeway are free-flowing, with less potential for conflict with vehicles traveling in the other direction. Left turns across traffic are also eliminated and potential conflict points are minimized.
When is a DDI the best interchange option?
A DDI works well in a high traffic area with relatively equal volumes of traffic coming from both directions. It also works best in areas where there are no conflicts with side streets or frontage roads in close proximity to the interchange. A DDI is also a cost-effective option that requires less land to purchase, so it is a good choice when funding is limited.
DDI animation for Pioneer Crossing