SR 172 is the main north–south highway through Poquoson and the primary access road to Langley Air Force Base and NASA's Langley Research Center.

The state highway meets the northern end of Armistead Avenue, which leads to the main entrance of Langley Air Force Base, as it curves to the north.

The state highway leaves the research center vicinity by crossing Brick Kiln Creek, a tributary of the Back River, into the city of Poquoson.

SR 172 expands to a five-lane road with a center left-turn lane as it approaches the center of Poquoson, where the highway intersects SR 171, which heads west as Victory Boulevard and east as Little Florida Road.

The state highway reduces to three lanes just south of its northern terminus at Poquoson Avenue.