Overview

Transit signal priority (TSP) reduces the amount of time buses spend waiting at traffic signals by shortening red lights or extending green lights. Technology in the traffic signal monitors the location of transit vehicles and estimates when they will arrive at an intersection, allowing the signal to adjust timing so buses can move through more efficiently.


Transit Signal Priority
An example of a green light extension.

An example of a green light extension.

TSP Benefits 

TSP can help improve bus service reliability and reduce time travel by minimizing red light delays.  

Over the course of its route, a SamTrans bus may spend up to 30% of its time stopped at red lights. Up to 20% of its time may be spent serving passengers at a bus stop, and just over half of the time is spent travelling.

For Route ECR, which takes approximately two hours to go from end-to-end, that equates to 30 minutes spent waiting at red lights.

Additional benefits:

  • Efficient service: By reducing time at signals, TSP helps SamTrans use buses more efficiently and can support faster vehicle turnarounds.
  • Improved customer experience: More consistent trips and shorter delays can make traveling by bus easier and more convenient for riders.
  • Fewer cars on the road: TSP encourages transit use, which reduces vehicle miles traveled and helps lower greenhouse gas emissions.
  • Compatible with emergency response: TSP can operate alongside emergency vehicle signal priority, which gives emergency vehicles priority at intersections.

TSP on El Camino Real  

In 2018, SamTrans received a $3.46 million grant from the Metropolitan Transportation Commission (MTC) to install a TSP system on El Camino Real. Working with local cities and Caltrans, equipment installation began in 2019, and the system was fully operational in 2021, covering 125 signalized intersections along the corridor.  

TSP-NOW Project

SamTrans launched the Transit Signal Priority Network Optimization Working Group (TSP-NOW) project in 2026 with city partners and neighboring counties to standardize and expand TSP in San Mateo County.  

Project goals:

  1. Optimize the existing TSP system on El Camino Real to achieve maximum benefit for Route ECR.
  2. Expand TSP to SamTrans’ most frequent routes to reduce bus delays and improve reliability.
  3. Develop countywide TSP standards that clarify policy, system architecture, agency roles and responsibilities, and funding strategy.
  4. Support cities in advancing traffic signal upgrades, emergency vehicle preemption, and other planning/policy goals.

SamTrans expects to complete a plan by the end of 2027 to implement TSP on its busiest routes. 

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