Transit Signal Priority along Metro’s new Rapid Ride C – and D – Lines
The Seattle Department of Transportation (SDOT) Signal Operations group is finally seeing the results of work done over the past five years to implement Transit Signal Priority (TSP) at key locations that are on Metro’s West Seattle Rapid Ride C-Line and the lower Queen Anne and Elliott Avenue W /15th and Ballard D-Line . These locations were jointly identified by Metro Transit and SDOT.
So you ask, how does TSP work? TSP equipment installed on a Rapid Ride bus sends a signal to the Metro equipment inside the large controller cabinet located near an intersection the bus is nearing. In turn, the Metro equipment in the cabinet is connected to the SDOT traffic signal controller which notifies it that a bus is approaching. The signal controller, programmed with the appropriate TSP timing parameters by SDOT, can then either extend the main street green light time or reduce or skip the side-street green signal in order to prevent the bus from having to stop, or to reduce the length of time the bus waits while at the red light and the side street traffic has the go-ahead.
As a result of this new technology, motorists approaching an intersection may notice the green light in their direction, and thus their forward movement, being skipped. Once the bus has passed through the intersection and the TSP call is removed, the controller will go through a recovery mode to get back to its original timing. With 10-minute arrival intervals on the rapid ride routes and travel in two (east/west and north/south) directions, synchronization of the traffic signals can be interrupted when the next bus comes through. The SDOT Signal Operations team has also programmed certain locations to serve the pedestrians or vehicles that have been waiting the longest time after a TSP interruption. The team will continue to fine tune the Metro equipment and settings for signal timing. The Aurora E-Line is planned to be in operation by late 2013.