Although originally planned, the plan for trains on line 7 to continue to Porte des Lilas was eventually abandoned, as trains on line 3 provided an adequate service on this branch (at the time, line 11 did not yet exist). Nevertheless, in order to connect lines 3 and 7, a shuttle was planned to run through the north connecting tunnel, later named "la voie navette". The Sprague-Thomson variant of rolling stock serviced this tunnel, taken from line 2. This variant measured in length and consisted of one train powered by two motors. With these changes, the "voie des Fêtes" and the Haxo station were left unused: the former serving as a train shed and the latter being left inaccessible to the public. The Gambetta – Porte des Lilas section and the shuttle were inaugurated on 27 November 1921.