lanes. Costs significantly less than a normal interchange. Disadvantages Drivers may not be familiar with configuration, particularly with regard to merging maneuvers along the opposite side of the roadway or the crossover flow of traffic. Pedestrian (and other sidewalk-user) access requires at least four crosswalks (two to cross the two signalized lane crossover intersections, while two more cross the local road at each end of the interchange). This could be mitigated by signalizing all movements, without impacting the two-phase nature of the interchange’s signals. Free-flowing traffic in both directions on the non-freeway road is impossible, as the signals cannot be green at both intersections for both directions simultaneously. Highway bus stops must be sited outside the interchange. Allowing exiting traffic to re-enter the through road in the same direction requires leaving the interchange on the local road and turning around, e.g., via a median U-turn crossover. This affects several use cases: Drivers who take the wrong exit Bypassing a crash at the bridge Allowing an oversize load to bypass a low bridge Further considerations No standards currently exist for this design. The design depends on site-specific conditions. Additional signage, lighting, and pavement markings are needed beyond the levels for a standard diamond interchange. Local road should be a low-speed facility, preferably under posted speed on the crossroad approach. However, this may be mitigated by utilizing a higher design speed for the crossing movements. Double crossover merging interchange A free-flowing interchange variant, patented in 2015, has received recent attention. Called the double crossover merging interchange (DCMI), it includes elements from the diverging diamond interchange, the tight diamond interchange, and the stack interchange. It eliminates the disadvantages of weaving and of merging into the outside lane from which the standard DDI variation suffers. A highway U-turn requires weaving, however. As of 2016, no such interchanges have been constructed. See also List of road interchanges in the United States Single-point urban interchange (SPUI) Jughandle Hook turn Michigan left Superstreet References Further reading External links DDI Guideline – A UDOT Guide to Diverging Diamond Interchanges, Utah Department of Transportation, June 2014 Transportation engineers discuss the design of the fifth U.S. DDI in Alcoa, TN Video of Paramics Traffic Simualtion software modeling a Double Crossover Diamond Interchange Diverging Diamond Interchange Visualization, Instructional video on how to drive in a DDI, NCDOTcommunications, published on 10 March 2011 Images of Diverging Diamond Interchange in Springfield, Missouri the