Impact of Phase Sequence on Cycle Length Resonance

Abstract

The concept of resonant cycle length, that there are certain cycle lengths that may provide excellent progression owing to corridor geometry and other factors, has some currency as a potential strategy for cycle length selection. Past studies have identified resonant cycles under certain conditions and demonstrated benefits from use of the strategy as a means of selecting cycle length. The present study revisited the concept in application to flow-based models of traffic signal performance, highlighting the impact of phase sequence optimization. The phenomenon of cycle length resonance was explored for corridors with equal and randomly generated spacing between intersections, and finally for a field-calibrated corridor. Under each scenario, the performance of different cycle lengths was explored under two optimization strategies: optimization of only offsets, and optimization of both offsets and phase sequence. It was found that phase sequence has a substantial impact on the performance of coordination. Optimized phase sequences were found to yield 8% to 14% improvement in performance compared with use of the default sequence. For corridors where a resonant cycle length was evident, when phase sequences could also be adjusted, the poorer performance of non-resonant cycle lengths could be mitigated by optimizing phase sequence. Although use of a resonant cycle length is likely to yield good performance for some corridors under appropriate conditions, the use of a phase sequence optimization strategy is likely to have a strong impact on most corridors, and could be more impactful than selection of a resonant cycle length.

Impact of Turning Lane Storage Length and Turning Proportions on Throughput at Oversaturated Signalized Intersections

“…Moreover, this work focused on one particular case study of a single intersection with protected left-turn phasing and no pedestrian interactions. The models developed here may not work well for adaptive or coordinated signal controls and factors like detector configurations or phase sequence can have impact on the models (28,29). Future work would seek to improve the proposed models through application to other field data with different scenarios to improve the transferability of the work and to develop factors that would allow the method to be more easily calibrated to any location and system.…”

Investigation of Resonant Signal Timing Plans through Comprehensive Evaluation of Various Optimization Approaches

“…As discussed earlier, another objective of this study was to document the performance of only eastbound (EB) and westbound (WB) coordinated through traffic to avoid a similar problem seen in previous studies, where the RCL, which is supposed to provide good two-way progression, was evaluated for the entire network and not only for progressed movements [13][14][15][16][17]. The performance measures used in this evaluation were still the same as in the network evaluation presented above, but they were aggregated only for the mainstreet through movements.…”

“…In that scenario, it was assumed that other signal timing parameters (e.g., offsets and phase sequences) were unchanged, regardless of volume fluctuations. Several follow-up studies investigated whether such a "resonant cycle length" could exist for various traffic conditions and network topologies [15][16][17]. More importantly, researchers expanded the optimization scope to include all signal timing parameters while looking for the RCL [15][16][17].…”

“…Several follow-up studies investigated whether such a "resonant cycle length" could exist for various traffic conditions and network topologies [15][16][17]. More importantly, researchers expanded the optimization scope to include all signal timing parameters while looking for the RCL [15][16][17]. Such an approach would essentially violate the true definition of the RCL, considering that all parameters are subject to optimization, and yet, only cycle length was denoted as being "resonant".…”

“…Another concern related to the RCL concept and previous studies is the evaluation approach of RCLs. In particular, while evaluating whether cycle length is resonant or not, most of the previous studies evaluated the overall network performance and not just the performance of progressed movements [13][14][15][16][17]. However, the overall network performance includes performance for side-street movements, and there seems to be a disbalance between how the RCL is defined and what constitutes the right measurement of two-way progression.…”