Boston-based Tufts Medical Center has won approval as a major trauma center, a designation that will change where ambulances take some of the region's most critically injured patients. Until now, Tufts has been the only major Boston teaching hospital not approved as an adult trauma center. As a result, ambulances carrying victims of car accidents, falls, or violence often bypassed that hospital for Beth Israel Deaconess Medical Center, Boston Medical Center, Brigham and Women's Hospital, or Massachusetts General Hospital, all state-designated trauma centers. Some doctors at other Boston hospitals have argued that the city has enough trauma centers and that to spend several million dollars to open another one is a poor use of resources.