Incorporating Phase Rotation into a Person-Based Signal Timing Optimization Algorithm

This article proposes a person-based traffic signal optimization algorithm that simultaneously optimizes signal phase sequence, cycle length, and green split to minimize total person delay at an intersection. It builds upon previous person-based work that uses a mathematical program to optimize signal timings based on real-time passenger car flows and knowledge of bus arrivals and passenger occupancies. Phase rotation is directly accommodated within the mathematical program by introducing new binary variables to describe the phase sequence. The program can either be solved directly or through an enumeration approach to reduce computational complexity. The proposed method is tested using numerical simulations of an intersection in Athens, Greece. The results reveal that phase rotation can reduce person delay significantly, especially when the intersection flow ratio is relatively low. These reductions in person delays are achieved by implicitly prioritizing the movement of high-occupancy buses to the detriment of lower-occupancy cars. Furthermore, to balance the person delay reduction and phase rotation frequency, a threshold can be applied in the phase sequence selection process to eliminate phase rotations actions with limited benefits.