According to Wikipedia http://en.wikipedia.org/wiki/Washing...Transit_Police they have jurisdiction thoughout the region:
More specifically http://en.wikipedia.org/wiki/Metro_T...ice_DepartmentTransit Police
Main article: Metro Transit Police Department
Congress established the Metro Transit Police Department (MTPD) on June 4, 1976. MTPD police officers have jurisdiction and arrest powers for crimes that occur throughout the 1,500 square mile (3,900 km2) Transit Zone that includes Maryland, Virginia, and the District of Columbia.
So - the question is -- was he going between Place A and Place B where he has jurisdiction, or was he going to that great restaurant his buddy told him about and almost missed his turn?Uniformed and plainclothes Transit Police officers patrol the Metrorail system and Metrobuses on foot and on bicycles, and using motorcycles and marked and unmarked police cars. Transit Police Detectives provide investigative support. Transit Police officers have jurisdiction and arrest powers throughout the 1,500-square-mile (3,900 km2) Metro service area for crimes that occur on Transit Authority facilities, or within 150 feet (46 m) of a Metrobus stop.
In any case, if you had a dash-mounted video camera you could have sent proof of his crappy driving skills to the WMATA along with a request to know just what they intend to do about it.