An Innovative Signal Phasing Scheme for Diverging Diamond Interchanges
Loading...
Authors
Bickett, Jeffrey Aaron
Issue Date
2023
Type
Thesis
Language
Keywords
DDI , Diverging Diamond Interchange , Phasing Scheme , Signal Optimization , Signal Timing
Alternative Title
Abstract
This thesis presents the development of an innovative signal phasing scheme for Diverging Diamond Interchanges (DDIs) through a case study of the diverging diamond interchange at Moana Lane & Interstate-580 freeway (Moana Ln & I-580 DDI) in Reno, Nevada.An innovative phasing scheme was derived and compared against four DDI phasing schemes that had been identified through field deployment or prior publications, and subsequently evaluated in this research effort categorized by two, three, and four critical movements. The strengths and weaknesses of using phase overlaps and dummy phases were outlined to achieve operational objectives regarding if internal stops and queueing were allowed and if signal control lost time can be minimized.The effectiveness of the developed signal phasing schemes was evaluated based on a case study where Moana Ln & I-580 DDI was used as an example. A set of 30-minute vehicle volume counts were collected during the both AM and PM peak hours and interpolated into full-hour traffic counts which were used for the analysis. As the PM peak counts were substantially greater than the AM peak counts, the analysis only evaluated the PM operations. The PM peak operations were primarily studied using a VISSIM model that was built and calibrated according to real-world geometry and traffic operations.Given a fully actuated PM timing plan implemented as the base scenario, comparative phasing schemes were tested under various conditions. Modified Webster’s equations were employed to produce phase splits for the phasing schemes with trailing overlaps. Split derivation was found to share characteristics with typical diamond interchanges, though the phasing varied. The phasing schemes with their optimized splits were then modeled in VISSIM simulation. A comparative evaluation was performed based on the simulated measures of effectiveness (MOEs), such as delay time, stop delay time, and average number of stops. Simulation results indicated that the proposed phasing scheme with internal stops could allow for reductions in traffic delay as compared to other schemes. The field condition of Moana Ln & I-580 DDI do not meet all requirements for implementing the optimal proposed phasing schemes, such as the absence of detection in interior lanes that eliminate internal stops or rewiring of the controller. Thus, the recommendation of the proposed phasing scheme only applies to certain conditions, such as new or renovated interchanges, which have been presented in the thesis. The findings presented in the thesis would facilitate transportation agencies making an informed decision on the development of traffic signal timing for a DDI for use in the field or for design alternative analysis.