The Columbia Pike Line, designated as Routes 16A, 16C & 16E, are daily bus routes operated by the Washington Metropolitan Area Transit Authority between the neighborhoods of Annandale (16A) or Culmore (16C, 16E) and Pentagon station (16A, 16C) of the Yellow and Blue lines of the Washington Metro or Franklin Square (16E).

Alongside the neighborhoods, it also brings service through the marketplace, business, and offices through Columbia Pike.

The 16A also runs through other neighborhoods in Columbia Pike, such as Lincolnia, Bailey's Crossroads, Barcroft, Arlington Heights, and Penrose.

Route 16A serves limited stops in Arlington County, bringing faster service between Bailey's Crossroads and Pentagon station.

The 16E only operates during late nights daily and early mornings on Saturdays and Sundays.

The 16 line provides premium reliable service in Columbia Pike to connect from neighborhoods, to marketplaces, to landmarks, and to business.

Route 16B runs between Pentagon station and the neighborhood of Culmore during weekday peak hours, while it extends to Annandale on the weekends.

Route 16F runs during peak hours only, serving to Pentagon Station in the morning, and the neighborhood of Culmore in the afternoon.

After 15 years of absence, WMATA reincarnated the 16C back in the Columbia Pike Line in 2018, with modifications from the old 16C route.

The 16F was proposed options to extend its weekday peak service to Downtown in Washington D.C.

On December 18, 2016, route 16E was extended from Pentagon station to Franklin Square in Downtown Washington D.C. due to earlier closures from Metrorail.

Route 16C also replaced the 16X from the Columbia Pike–Federal Triangle Limited Line, which operated up to Federal Triangle in Washington D.C. By bringing more reliable and faster service, the 16A & 16C serves limited stops on Columbia Pike in Arlington County.

During WMATAs 2021 Fiscal Year budget, it was proposed to eliminate route 16C towards Downtown DC to reduce redundancy with the Blue and Yellow Lines and to fully eliminate route 16E which will be replaced by restored late night Metrorail service.

[16] Route 16C has not operated to Federal Triangle since March 13, 2020 due to Metro's response to the COVID-19 pandemic.