Diverging Diamond Interchange
What is a DDI?
A DDI is an engineering concept that originated in France and has been refined for various locations throughout the U.S. The configuration briefly channels traffic to the opposite side of the road to provide easier and safer access on and off the freeway. DDIs reduce the number of signal phases needed to move motorists through an interchange and efficiently move high volumes of traffic without increasing the number of lanes.
How safe is a DDI?
Safety has been critical to determining the viability of DDIs. Crossing traffic to the left side of the road and eliminating left-turns across traffic makes movements on and off the freeway more free-flowing and minimizes potential conflict points.
When is a DDI the best interchange option?
DDIs work well in high-traffic areas with relatively equal volumes of traffic coming from both directions. They also work best when there are no side streets or frontage roads nearby.
Are there other DDIs in Utah?
While the 1100 South DDI is the first in northern Utah, it will be the seventh in the state when complete. UDOT opened Utah's first DDI and the United States' second in 2010 at American Fork Main Street and I-15. Due to their success in improving traffic flow, DDIs have been dotting the country ever since.
Are DDIs fiscally responsible?
DDIs provide significant cost savings because their small footprint does not require the purchase of right of way and, if replacing an interchange, they utilize as much of the existing interchange as possible.
American Fork Main Street DDI Animation