MetroExtra is a limited-stop service operated by the Washington Metropolitan Area Transit Authority, which operates on Metrobus lines that need extra service with faster trips.

[1] The route would follow its local counterpart but only serve the most important stops.

In 2008, a study was released along the 16th Street corridor to improve the line by both WMATA and the District Department of Transportation.

The corridor averages a weekday ridership of 16,000 making it the third most heavily used line in the Metrobus system, Parts of the proposal were to create a new route S3 which would be shortened routes S1, S2, and S4, and create a limited stop route S9.

The route would provide limited stop service supplementing the Veirs Mill Road Line.

The route would operate between Rockville station and Wheaton station and be the first Metro Extra route to operate exclusively in Montgomery County, Maryland.