Transit Signal Priority
In July 2024, Metro, in partnership with the City of Portland, began testing our Transit Signal Priority (TSP) system. TSP allows buses to communicate with traffic signals in order for signals to adjust timing to allow transit vehicles to get through intersections faster. TSP equipment is installed on all Metro buses, and 32 traffic signals in the City of Portland.
Benefits
Transit Signal Priority has the following benefits:
Improved travel time for passengers: Passengers get to their destinations faster. Travel times for bus passengers become more competitive with driving a personal vehicle.
Improved on-time performance: Buses experience less traffic delay thanks to TSP, meaning buses arrive on time more consistently. This means less wait time at bus stops, more reliable transfers between services, and a more reliable, predictable transit system.
Less fuel used: Buses use more fuel when they are accelerating, and fuel is used while idling at a red light. TSP allows buses to arrive at green lights more often, reducing the need to stop and re-accelerate.
How does Transit Signal Priority work?
Transit Signal Priority moves buses through intersections faster by allowing buses to communicate with traffic signals. Typical traffic signals often adjust signal timings to account for the presence of traffic (providing a green light for a side street only when traffic is present) or for heavy traffic (providing extra green time for an approach where traffic has backed up significantly); however, most signals do not treat different types of vehicles differently. TSP allows traffic signals to give buses — vehicles that can carry dozens of people — priority over passenger vehicles.
TSP generally works in one of the following ways:
Green Extension: As the bus approaches a green light, the signal timing adjusts to hold the green light longer, allowing the bus to get through the intersection.
Truncated Red: As the bus approaches a red light, the signal timing adjusts to turn the signal green ahead of schedule, so that the bus arrives on a green light, or has to wait at the red light for a shorter period of time than it otherwise would have.
Queue jumping: Allows a bus to proceed through an intersection when the rest of traffic is stopped, allowing it to get ahead of long queues of vehicles. This is typically only possible with a dedicated transit lane or if the bus is making a left turn. In many cases, a specific transit signal is required to allow a bus to proceed where general traffic has a red light.
Where will TSP equipment be installed?
TSP equipment has been installed at Portland-area intersections with upgraded traffic signals. Some intersections do not have traffic signal controllers that are compatible with TSP equipment. As the region updates traffic signals, more locations will be eligible for TSP installations.
TSP has been installed at intersections on Congress Street, Brighton Avenue, Forest Avenue, and Washington Avenue in Portland. Additionally, signals on Auburn Street, Preble Street, and William Clarke Drive have also been equipped. This means that TSP will improve operations across nearly all Metro routes.
More Information
More information on Transit Signal Priority can be found here:
