The 4A and 4B operate from Four Mile Run Division on various schedules. The 4A only operates during rush hours, while the 4B operates on a daily schedule. The 4A does not serve the neighborhoods of Courthouse, Lyon Park or Buckingham, but operates the entire route via Arlington Boulevard. The 4B runs through the neighborhoods in Arlington County, where the 4A does not operate through between terminals. The 4A and 4B run through the same intervals, as the route splits between Arlington Forest and Rosslyn station.
History
The Pershing Drive–Arlington Boulevard Line was introduced in 1926, as the route was part of the Washington Virginia & Maryland Coach Company. It was later operated by WMATA in 1973, when it acquired all routes from the WV&M. Since 1973, the Pershing Drive–Arlington Boulevard Line consists of all 4 line. The 4 line provides reliable service within Fairfax and Arlington counties to connect from neighborhoods, to marketplaces, to landmarks, and to business. The Pershing Drive–Arlington Boulevard Line is a unique line, in which it retains its original name, without changing its name during service changes, despite that it ran under the Arlington Boulevard Line when it was operated by the WV&M. After WMATA acquired the 4 line in 1973, the 4 line have its former terminus throughout the years. The 4A once operated between Rosslyn Metro and Culmore vía Arlington Boulevard. The 4B operated once to Jefferson Village, a neighborhood in Fairfax County. There was also routes 4E, 4H, and 4S which is part of the line alongside with routes 4A and 4B. Routes 4E, 4H, and 4S all operates up to Rosslyn station alongside with the 4A and 4B, however, the 4E starts from the neighborhood of Arlington Forest, the 4H from Seven Corners, and the 4S from Sleepy Hollow Road in Fairfax County. The 4A operates during weekdays, while the 4B ran daily, the 4E runs on a one way route during morning rush hours, the 4H runs during late night and Saturdays, and the 4S runs during rush hours, morning peak to Rosslyn and afternoon peak to the neighborhood of Sleepy Hollow.
1981 Changes
On January 4, 1981, the 4B was truncated from Jefferson Village to Seven Corners.
On September 24, 2006, route 4S was replaced by the 4H, no longer operating to Sleepy Hollow. 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.
January 2012 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. The schedules of these trips remains unchanged, however, the 4B and the 4H will no longer alternate terminals at Leesburg Pike.
2013 Proposed Changes
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. 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. 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.
December 2013 Changes
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. 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. 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. 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. 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.
