Public transit buses face many operational challenges—especially when operating on the same streets and roads as other vehicles. Buses can be slowed by traffic congestion and get repeatedly caught at traffic lights, slowing buses down and delaying both passengers on board and passengers waiting at stops farther along the route.

The TRB Transit Cooperative Research Program's TCRP Synthesis 149: Transit Signal Priority: Current State of the Practice documents the current practice of TSP, which is an important tool that increases bus speeds and reliability, thereby improving transit system efficiency and effectiveness.

Twenty-eight (61%) of the 46 surveyed transit agencies had active TSP deployments, and 13 transit agencies (28%) either are in predeployment testing or have plans to pursue TSP in the future.