  Traffic congestion in urban areas is a significant problem, leading to
prolonged travel times, reduced efficiency, and increased environmental
concerns. Effective traffic signal control (TSC) is a key strategy for reducing
congestion. Unlike most TSC systems that rely on high-frequency control, this
study introduces an innovative joint phase traffic signal cycle control method
that operates effectively with varying control intervals. Our method features
an adjust all phases action design, enabling simultaneous phase changes within
the signal cycle, which fosters both immediate stability and sustained TSC
effectiveness, especially at lower frequencies. The approach also integrates
decentralized actors to handle the complexity of the action space, with a
centralized critic to ensure coordinated phase adjusting. Extensive testing on
both synthetic and real-world data across different intersection types and
signal setups shows that our method significantly outperforms other popular
techniques, particularly at high control intervals. Case studies of policies
derived from traffic data further illustrate the robustness and reliability of
our proposed method.
