Réseau Saint-Lazare

Réseau Saint-Lazare is the network of railway lines originating from Saint Lazare Station in Paris. The network stretches from Paris to Normandy and encompasses suburban services. Parisian suburban rail services are operated under SNCF's brand name Transilien. Intercity services are also operated by SNCF but under the brand name Corail.

Cohabitation of both intercity and suburban rail did cause problems. Junctions were not carefully planned, and extensions were simply grafted onto the existing network. The Chemins de Fer de l'Ouest's suburban network was particularly touched by problems of cohabitation on the line and at stations since it had the largest suburban network in France. The problem resided in the fact that lines crossed each other, creating unnecessary bottlenecks and hold ups. In 1880, the Chemins de Fer de l'Ouest operated four lines out of Saint-Lazare: the lines to Versailles Rive Droite and Argenteuil separated at Asnières whilst the lines to Saint-Germain and Rouen separated at Colombes. As they were, both lines to Argenteuil crossed those to Saint-Germain and Rouen at Asnières. The Chemins de Fer de l'Ouest thus decided create a spur, opened in 1891, from Bécon-les-Bruyères and La Garenne-Colombes. In 1892, the line to Saint-Germain was rerouted to a spur of the line to Versailles instead of the line to Poissy whilst the line to Poissy was rerouted to a spur of the line to Argenteuil, avoiding crossings. The bridge over the River Seine still had four tracks, but serving two pairs of lines. These modifications were only sufficient for a time as traffic was in constant increase, growing from 26 million passengers in 1888 to 42 million in 1898. The tunnel at Batignoles (now Pont Cardinet) was another bottleneck, so a fourth tunnel was built, but later demolished along with all save one tunnel in 1912. At that time, the Chemin de fer de l'État possessed eight tracks leaving Saint-Lazare, which were split into four groups:

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