Work began in 2007 and was largely carried out without interrupting passenger traffic. Preliminary work involved electrical and signaling upgrades throughout the entire line. Work also commenced on converting the original Porte Maillot station (also known as "Espace Maillot") into a light maintenance facility for the MP 05 rolling stock. In 2009, work commenced on installing platform screen doors; with Bérault and Porte Maillot being the first stations to be equipped. Due to its curved platform, Bastille (in 2011) was among the last stations to be equipped. During this time, individual stations were intermittently closed to allow platforms to be leveled with the height of the train floors (from :fr:Ligne 1 du métro de Paris).