This branch mostly used the infrastructure of the "ligne d'Auteuil" (incorporated into the "ligne de petite ceinture" from 1867, closed to passengers from 22 July 1934), and a new 3 kilometers tunnel connection between Batignolles and St-Ouen, connecting to the RER C's main trunk at Champ de Mars-Tour Eiffel via a curved bridge (the only one in Paris) over the Seine river.