South Portland, Maine recently installed the EMTRAC system to provide Transit Signal Priority (TSP) for their South Portland Bus Service. As a part of the TSP implementation project, city personnel worked with their consulting traffic-engineering firm, Sebago Technics, Inc., to conduct a study to determine the general benefits of TSP in South Portland and to compare RF/GPS-based TSP with optical-based TSP to determine if one technology outperformed the other.