This paper summarizes three implementations of transit signal priority in North America. While the paper mainly discusses the institutional and technical elements of each implementation, it does highlight some impacts.
After implementing traffic signal priority for a light-rail transit (LRT) line along an urban arterial in Toronto, system operators were able to remove one vehicle from service and maintain the same level of service to passengers along the corridor. This reduction in equipment reduced operating costs. However, the transit agency had some concern with system operations at intersections with near-side LRT stops. The system caused increased delay to the transit vehicle by extending the green time while the vehicle dwells at the stop, typically reaching the maximum phase length permitted before the vehicle finishes allowing passengers to board. This increases the time that the vehicle must wait at the stop for the following green phase. The system operators have also received complaints regarding increases in pedestrian delay due to the signal priority system.
Experience with a transit priority system implemented on a bus line along an urban arterial in Vancouver, British Columbia has revealed some positive benefits. The system has reduced the variability of travel time experienced by buses along the route by 29 percent in the AM peak and 59 percent during the PM peak. The system only permits transit vehicles to obtain signal priority if they are behind schedule as the vehicle approaches the intersection.