The objectives of this research are to provide NCDOT and other agencies in North Carolina with objective, scientific guidance on how DDIs compare in a corridor context, and more importantly how the DDI performance can be improved by using the available capacity offered by the efficient two-phase signals. With NCDOT being on the forefront of unconventional intersection designs, superstreet intersections are one high-potential treatment for intersections adjacent to a DDI, which similarly allow for a two-phase signal operation. However, other alternatives exist such as 1) using a half-cycle concept to better integrate short DDI cycles with long cycle lengths at adjacent intersections, 2) using other alternative intersections ideas, 3) signal timing strategies (creative lead/lag timing), or 4) considering other geometric improvements to increase capacity. In particular, the project will inform the NCDOT on which variations and alternatives might be worthy of detailed analysis given set of demands and a physical context.
The main thrusts of the proposed research are to identify a list of DDI corridor variations, determine which of those are worth testing, to design those variations and alternatives, to simulate those variations and alternatives for traffic operations, and to estimate other measures for those variations and alternatives. The primary research products will be recommendations on whether and where NCDOT and other agencies should use the various DDI variations and with what configuration of adjacent intersections. The recommendations can be implemented by traffic engineers, planners, and designers at many stages of thinking about interchange improvements, from new TIP projects to quick safety countermeasures.
