A Comparative Analysis of Diverging Diamond Interchange Operations

Travel demand is steadily increasing all over the country. This is pushing the limits of our existing roadway infrastructure. The need to provide additional capacity is constantly at odds with the potential impacts that transportation improvements have on existing developments. The diverging diamond interchange (DDI) is an innovative new concept being pursued as an alternative interchange type that may provide a significant increase in capacity while actually reducing the bridge size requirements. This paper will discuss the operational benefits of the DDI in comparison to a diamond and a single point urban interchange. The DDI appears to be an option that can greatly improve operations and capacity at the ramp terminal intersections. The operations of the DDI will be compared to the operations of other interchange types which will also allow for a planning-level assessment of the differences in the interchange footprints. This interchange concept is based on a standard diamond interchange with the key difference being a shift in the crossroad traffic in the interchange. Traffic on the crossroad crosses paths twice as traffic is shifted to the left side of oncoming traffic allowing left turn movements t