Massachusetts Bay Transportation Authority Police
The Massachusetts Bay Transportation Authority Police (also known as the T Police or Transit Police and colloquially known as the "Subway Cops") is a police force which has primary jurisdiction on Massachusetts Bay Transportation Authority (MBTA) property and vehicles in the 177 municipalities within the MBTA district. The department has an authorized size of 266 officers and 10 civilians.
Source: Wikipedia — Massachusetts Bay Transportation Authority Police (CC BY-SA 4.0)