northern virginia is part of the washington metropolitan area of the united states, and its surface transit system is integrated with that of the city of washington, d.c. however, because of the potomac river separating northern virginia from the city, the two systems have evolved largely independently. at present, most major bus routes, including all that cross the potomac, are operated by the washington metropolitan area transit authority (wmata), while several smaller systems are city- or county-owned. since the washington metro opened to virginia, most of the bus routes have terminated on either side of the potomac river, where passengers can transfer to the rapid transit system, or to one of the few wmata metrobus routes that cross the river (route 38b).