Article Transportation Research Record 1–11 Ó National Academy of Sciences: Transportation Research Board 2018 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0361198118792330 journals.sagepub.com/home/trr Large-Scale Transit Signal Priority Implementation: District of Columbia’s Path to Success Bailey Lozner 1 , Kevin Lee 2 , A. Wasim Raja 3 , Mohammed G. Habib 3 , and Burak Cesme 1 Abstract In 2016, the District Department of Transportation (DDOT) deployed transit signal priority (TSP) at 195 intersections in highly urbanized areas of Washington, DC. Years before deployment, DDOToutlined a multi-year process that would aid in the realization of their ambitious objectives. In collaboration with a broader regional implementation and in partnership with the Washington Metropolitan Area Transit Authority (WMATA), DDOT set out to apply a systems engineering driven pro- cess to identify, design, test, and accept a large-scale TSP system. Application of this systems engineering process led to the successful, widespread deployment of TSP in an urbanized operating environment. Although numerous research efforts to date focus on smaller scale efforts, this paper seeks to close gaps in the literature with a process-focused case study, high- lighting intersection selection, system verification testing, and validation for acceptance as applied by DDOT for establishment of an operational, large-scale system. The paper concludes with a discussion of the lessons learned. A decade ago, the vison for bus transit in the National Capital area was a fully integrated, regional system that would bring a quality, reliable service to riders across the region. The vision was ambitious, calling for large-scale bus service improvements across state lines. With these improvements as motivation, regional agencies embarked on a collaborative journey to implement priority treat- ments for Washington Metropolitan Area Transit Authority (WMATA) bus routes. Among these improve- ments was the implementation of transit signal priority (TSP) on nearly a dozen routes operating throughout the District of Columbia, northern Virginia, and areas of Maryland. One agency, the District Department of Transportation (DDOT), worked in concert with the regional stakeholders to spearhead the deployment of TSP in the District. Through rigorous planning and application of a systems engineering process, DDOT brought the vision of a large-scale TSP system to frui- tion, deploying the functionality at nearly 200 traffic sig- nals. The process the agency utilized for successful implementation of a large-scale TSP system is the subject matter of this paper. TSP is a tool used to improve transit performance and reliability. The operational strategy facilitates the move- ment of transit vehicles through traffic signals, resulting in reduced transit travel times, improved schedule adherence, improved transit efficiency, and increased road network efficiency as measured by person mobility (1). The most common TSP strategies either extend a phase to allow a transit vehicle to pass (i.e., green exten- sion) or terminate conflicting phases to allow early ser- vice and reduce red time (i.e., red truncation, or early return to green) (2). These signal timing adjustments can result in reduced transit delay when applied at signalized intersections. TSP has been utilized for decades to improve transit service in urbanized and suburban areas across the U.S.. Research shows that overall route travel time reductions of up to 10% with the implementation of TSP are common. Priority systems also have shown to reduce variability in bus delays, thereby increasing relia- bility (3). Common U.S. implementations of TSP are at the cor- ridor level; large-scale TSP deployments in urban operat- ing environments are much less common, and research 1 Kittelson & Associates, Inc, Washington, DC 2 Kittelson & Associates, Inc., Cincinnati, OH 3 District Department of Transportation, Washington, DC Corresponding Author: Address correspondence to Bailey Lozner: blozner@kittelson.com