Pershing Drive–Arlington Boulevard Line

On January 4, 1981, the 4B was truncated from Jefferson Village to Seven Corners.[2]

On September 24, 2006, route 4S was replaced by the 4H, no longer operating to Sleepy Hollow.[4] These changes brings in more service for the 4H, operating during rush hours where the 4S usually runs. The 4H retains its original intervals following these changes.

The new Seven Corners Transit Center opened on January 22, 2012 next to Seven Corners Shopping Center. The 4A, 4B, and 4H was rerouted to serve the new transit center to connect with other routes.[5] The schedules of these trips remains unchanged, however, the 4B and the 4H will no longer alternate terminals at Leesburg Pike.

In 2013, WMATA proposed to restructure the 4A, 4B, 4E, and 4H. Route 4A was to discontinue all service between Culmore and Seven Corners Transit Center.[6] Service will be provided by the 26A, as it operates via Leesburg Pike. It was also to reduce travel times to Rosslyn station, as riders can transfer via East Falls Church station, where the 26A will operate. Route 4E was proposed to be converted to the 4B, to reduce redundancy to the 4B during morning peak hours. Route 4H was proposed to be converted to the 4A, to reduce redundancy to the 4A during peak hours.[6] The 4A will be designated to operate via Arlington Boulevard, and the 4B to operate via North Pershing Drive.

The reason why WMATA planned these changes was to reduce low ridership on the segment between Culmore and Seven Corners, and to clear bus bunching in the line. These changes was also to improve on-time performance of the route.[6]

On December 29, 2013, major changes occurred in the 4 line. The 4H was discontinued and is replaced by the 4A, and the 4E was converted into 4B trips.[7] These changes was made to clear up bus bunching, as the 4E have the same stops as the 4B, and the 4H have the same stops as the 4A. Alongside with these changes, the 4A was truncated to Seven Corners. Alternate service to Culmore via Leesburg Pike was replaced by the Annandale–East Falls Church Line (route 26A). The 4A have Saturday service following the discontinuation of the 4H.

On June 26, 2016, Saturday service of the 4A is eliminated, making the route a weekdays only route.[8] The 4B remains unchanged, but now operates every 45 minutes on Saturday.

On June 24, 2018, the 4A midday service was eliminated, having the route to operate only during rush hours.[9] All off-peak trips is now operated by route 4B. The short morning rush hour 4B trips is now extended from Arlington Forest to Seven Corners Transit Center, to improve ridership in the 4B. The bus frequency of the 4B was increased, from 60 minutes to 30 minutes on middays, and 75 minutes to 60 minutes on Sundays.

On September 10, 2020 as part of its FY2022 proposed budget, WMATA proposed to eliminate route 4A service in order to reduce costs and low federal funds.[10] WMATA also proposed to reduce weekend frequency on route 4B.