Auteuil at Pont Cardinet freed up platforms at Saint-Lazare and increased tracks in the tranchée des Batignoles from eight to ten and split in five groups: Groupe I: Auteuil, leaving Pont Cardinet Groupe II: Versailles Groupe III: Saint-Germain Groupe IV: Argenteuil Groupe V: Mantes, via Poissy Groupe VI: Mantes, via Conflans An eleventh track, used for servicing, was built for reversing locomotives. The pont d'Asnières was widened to accommodate the ten tracks. A saut-de-mouton (flying junction) was built between Asnières and Bois-Colombes to avoid the crossing of the groupe IV and groupe V lines. Two joining lines were built in 1923 and 1925 at La Folie and Bezons to relieve suburban lines from goods services. The station building at Bois-Colombes was rebuilt above the railway line in 1934 as well as the quadrupling of the line as well as replacement of all the remaining level crossings by bridges or underpasses between 1933 and 1935. The line was also rebuilt on a 585 m long viaduct between Bois-Colombes and Le Stade (Gennevilliers). Other modernisation projects included the electrification of the Réseau Saint-Lazare. Electrification Third rail electrification The Chemins de fer de l'Ouest had hoped to electrify parts of its lines to Saint-Germain and Argenteuil as early as 1908. Many of the construction work on the lines were initiated to alleviate operational issues but steam traction meant that without remote driving or the locomotive, engines had to be turned around the train at termini. Third rail electrification had been applied to Paris' underground and the Chemin de fer de Paris à Orléans's line from Les Invalides with success. Rolling stock chosen were two carriage 22m long EMUs of Z 1300 class resting on two bogies and compatible with rolling stock used on the line at Les Invalides. 1500 V overhead electrification had been dismissed by the French Government following World War I and so 650 V third rail electrification was chosen. A special commission had found that the Réseau État Saint-Lazare was in need of electrification on the railway lines to Saint-Germain, Versailles Rive Droite, Saint-Nom-la-Bretèche, Puteaux, Issy-les-Moulineaux and Argenteuil. The Chemins de fer de l'Ouest and then the Chemin de fer de l'État from 1909 had worked towards that goal by simplifying track layout in Paris' close suburbs. On 24 April 1924, the third rail was switched on groupe II on the 6 km section between Paris and Bécon-les-Bruyères and on