Transit Signal Priority

About TSP

Transit Signal Priority (TSP) helps buses move more efficiently through city streets by giving them better coordination with traffic signals. This technology improves on-time performance, makes transfers between buses easier, and enhances the overall rider experience. By reducing the time buses spend idling at intersections, TSP also lowers gas emissions and cuts fuel costs. In some cases, it can even shorten travel times enough that fewer buses are needed to provide the same level of service—delivering both customer benefits and operational savings. Recognizing these advantages, RTD has adopted a centralized could-based TSP system along major transit corridors to improve bus speed and reliability.

TSP Concept of Operations

Typically, TSP operation allows traffic signal controllers to skip conflicting signal phases, to shorten conflicting phases, to lengthen compatible phases, or to modify phase sequence to serve the transit vehicle. Two primary TSP strategies are 1) Green Extension and 2) Early Green (Red Truncation). More specifically:

• A green extension strategy extends the green time for the TSP movement when a TSP-equipped transit vehicle is approaching. The green extension is one of the most effective forms of TSP since a green extension does not require additional clearance intervals.
• An early green strategy shortens the green time of the preceding phases to expedite the return to green (i.e., red truncation) for the movement where a TSP-equipped vehicle has been detected. This strategy only applies when the signal is red, and a TSP-equipped vehicle is approaching. Both green extension and early green strategies are available together within TSP enhanced control environment but are not applied to the same signal cycle.

RTD TSP System Architecture

RTD has implemented a centralized, cloud-based Transit Signal Priority (TSP) system that capitalizes on existing cellular communications and on-board technologies. This modern approach integrates seamlessly with RTD’s Computer-Aided Dispatch/Automatic Vehicle Location (CAD/AVL) and Automatic Passenger Counting (APC) systems to enable real-time, data-informed TSP system. As a bus approaches a TSP-equipped intersection, the system evaluates schedule adherence and passenger load. If thresholds are met, a signal priority request is transmitted to the jurisdiction’s traffic controller. This strategy enhances service reliability, supports operational efficiency, and minimizes the need for new infrastructure investments.

TSP Application Reference Materials and Contact Info

Several reports on Transit Signal Priority (TSP) have been developed for public reference. To request a copy or ask questions about Transit Priority (e.g., TSP, Queue Jump, Bus Bypass), please contact [email protected]. Key reports include:

• RTD Transit Signal Priority (TSP) Application Guidelines (2019): An internal guide outlining what TSP is, its benefits, and key considerations for implementation. It provides step-by-step guidance for developing TSP projects within RTD. Please note that portions of the report are now outdated due to policy updates and system changes.
• Before-and-After TSP Study (2021): An analysis of bus performance, including dwell times, speeds, travel times, and on-time performance before and after TSP deployment. Findings are used by RTD and stakeholders to adjust operations—for example, updating bus schedules or modifying signal timing to improve both transit and general traffic flow.
• Regional TSP System Architecture Report (Phase 1) (2025): Developed to address the growing interest in TSP from different jurisdictions using varying systems in the region. The report summarizes the work of the Regional TSP Working Group, formed by RTD in partnership with the Denver Regional Council of Governments (DRCOG). It outlines a unified strategy and technology framework for deploying next-generation TSP across the Denver metro area, including RTD’s centralized cloud-based system and a Connected Vehicle (CV) pilot in Denver.

Several regional reports have also examined the use of transit priority strategies to guide the planning of future capital improvement projects. Key reports include:

• The Regional BRT Feasibility Study (2019): The study evaluated future corridors within the RTD service area through a data-driven tiered evaluation process. At the conclusion of the study, three to five corridors were identified for future bus rapid transit investment. https://www.rtd-denver.com/about-rtd/projects/regional-bus-rapid-transit-feasibility-study
• The Mobility Choice Blueprint (2019): Mobility Choice Blueprint is a collaborative strategy to prepare the Mile High region for rapidly changing technologies that are transforming the way we travel. We are collectively helping to define the region’s mobility future through a more connected, mobile, adaptable and user-driven network.