Globally, multi-modal transportation agencies constantly struggle to balance both efficiency and safety between various forms of pedestrian, vehicular, and transit traffic. City traffic systems must rely on street design and precise signal engineering to influence millions of human and mechanical movements daily. Considering the myriad traffic variables influencing these systems’ performance, it is difficult or impossible for transit agencies to satisfy all transportation users simultaneously. San Francisco’s traffic signal retiming project demonstrates firsthand how protecting pedestrian safety can come at a cost to transit efficiency.