Traffic Signal Priority

Benefits of TSP

There are several benefits of using TSP, including improved transit reliability, reduced transit travel times, reduced stops (less wear and tear on equipment), increased rider comfort, and reduced emissions. Because TSP allows for smoother flow of transit vehicles, they can move from point to point, as well as to final destinations, on time more often.

Research shows that this increased reliability is a critical need for any transit to become successful. Because the vehicles are sitting on red signals for a much smaller amount of time, the trips can be faster, making transit attractive for riders. This reduction in travel time can also allow for fewer buses to serve a particular route, which can result in reduced operating costs. When vehicles do not stop at every signal, the wear and tear on the vehicle and equipment, as well as that of the pavement, is reduced.

Vehicular emissions result from a combination of distance traveled, speed, acceleration, deceleration, and fuel, among other factors. A smoother flow facilitated by TSP can give the vehicles a relatively constant speed and less need for frequent stops, acceleration, and deceleration—resulting in reduction in emissions. An aggressive level of prioritizing transit over general traffic, as seen in many European countries, can reward transit usage and help reduce traffic congestion.

The cost of TSP is mainly attributed to equipment. Sensors and communication equipment need to be installed at intersections, as well as in vehicles. Complex designs and greater functionality can increase the cost. Another important expense is to upgrade the signals and controllers. Further cost is incurred in setting up control centers and training personnel.

TSP Methods

TSP can be employed on a location-to-location basis or on a systemwide basis. Systemwide TSP requires the employment of advanced technologies—one example is an automated vehicle location (AVL) system.

Passive TSP techniques involve optimizing signal timing or coordinating successive signals on a corridor. This technique allows for longer green time on the main street and a series of signals that stay green, which will allow the transit vehicle to move along smoothly. This can perform well when there is a significant amount of transit service on a street with high frequency. Passive techniques are cost-effective measures because they do not require specialized technology (for example, bus detectors).

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