Addison is a station on the Chicago Transit Authority's 'L' system, serving the Blue Line. This article or section does not cite any references or sources. ... Image File history File links Straight_Line_Steady. ... Exterior open entrance to a metro station (Tribunal station in Madrid) A metro station is a railway station for a rapid transit system, often known by names such as metro and subway. It is often underground or elevated. ... Chicago Transit Authority, also known as CTA, is the operator of mass transit within the City of Chicago, Illinois. ... The L[1], variously, if perhaps incorrectly, styled L, El, EL, or L, is the rapid transit system that serves Chicago, Illinois in the United States. ... This article or section does not cite any references or sources. ...