An Advanced Signal Phasing Scheme for Diverging Diamond Interchanges

43 A diverging diamond interchange (DDI), also called a double crossover diamond interchange 44 (DCD), is a relatively new interchange type in the U.S. Due to its many advantages over the 45 conventional diamond interchanges such as higher capacity and lower delay, there has been a 46 growing interest in its analysis methodologies and operational strategies. DDIs have shown 47 particularly high efficiency under conditions with heavy ramp traffic to arterial roads. However, 48 as the DDI concept is relatively new in the U.S., the research on DDIs is still considered to be in 49 the preliminary stage. In particular, most studies found in the literature only provided basic 50 phasing schemes, which were not optimized for efficiency. Furthermore, there is a lack of 51 commonly acceptable methodologies for obtaining critical signal control parameters, such as the 52 cycle length, and phasing splits. Therefore, it is an area topic in need of much research in order 53 to develop signal phasing schemes for achieving the optimized DDI performance. This study 54 proposed a new methodology for signal phasing scheme design at DDIs. With minor adjustment, 55 it can be applied to a variety of DDIs with different traffic demands and geometric 56 configurations. The proposed phasing design approach was specifically designed for DDIs, so it 57 could be employed as a guide or a reference for signal timing design at DDIs. At the DDI of 58 Moana Ln and U.S. 395 in Reno, Nevada, the proposed scheme was evaluated and compared 59 with various signal phasing schemes by using the hardware-in-the-loop simulation technology. 60 The simulation results indicated that the proposed approach significantly outperformed the one 61 currently being used at this interchange. 62