A Diverging Diamond Interchange (DDI) is a relatively new design that allows for more efficiency and higher capacity than a traditional diamond interchange. Through-traffic on the arterial is crossed from the right side to the left at the signal prior to the interchange bridge and crossed back at the signal after. This allows left turns from the exit ramps to flow freely without a protected signal phase, which in turn reduces the number of signal phases from three to two. This makes the signal operation more efficient, resulting in better operation and higher capacities. Missouri may be the first in the U.S. to implement the DDI as part of an interchange project. In 2007, a planning study in Lexington, Ky recommended a DDI at one interchange location.