Линия U Transilien: История и развитие парижского пригорода

Transilien Line U, also known as "La Défense La Verrière" or more often simply "ligne U", is a tangential commuter train link, which serves the western Paris region from La Défense. It links the Paris's business district of La Défense to La Verrière station, in the south west of Ile de France. It is the only commuter train line in the Transilien network that does not originate from a large Parisian station. The line has 55,000 passengers per weekday in 2014.

22 July 1988: A proposal is submitted to the Syndicat des transports parisiens for a suburb to suburb tangentielle line between Saint Quentin en Yvelines and the business district of La Défense. July 1991: The proposal is approved by the Syndicat des transports parisiens, with the line reusing existing infrastructure from the Grande Ceinture line. 28 May 1995: The La Défense–Saint Quentin en Yvelines line is opened to the public. end of 2004: The line is renamed Line U as part of a reworking of the Transilien network.

On August 2, 1839, the current section linking La Défense to the Viroflay connection was put into service as part of the line from Paris Saint Lazare to Versailles Rive Droite. The latter is the second created in Île de France after the line from Paris Saint Lazare to Saint Germain en Laye. It makes it possible to link Paris to Versailles in a shorter time, to bring many visitors to the castle, which is at the end of its restoration, and to bring economic development to the region. The line is the result of the project of a bridge and road engineer, Desfontaines. He had proposed to join the line of Versailles right bank to that of Saint Germain, which limited the costly expropriations, and also restricted the ramp to a value of 5 mm / m, at the cost of a slightly longer route. On July 12, 1849, the section between the Viroflay connection and La Verrière station was opened in turn, as part of the line from Paris Montparnasse to Brest. In July 1852, the lines from Paris Saint Lazare to Versailles Rive Droite and from Paris Montparnasse to Brest were linked together through the Viroflay connection. On July 22, 1928, the section going from the current station of La Défense to the Viroflay connection (Line from Paris Saint Lazare to Versailles Rive Droite) was energized, in direct current 650 V by 3rd rail. This electrification is accompanied by the generalization of high platforms, the replacement of its ancient steam traction equipment, much criticized for its discomfort, by modern “Standard” trains, which remained emblematic of the Saint Lazare suburb for more than fifty years
In April 1959, a new stop was created on the line to La Défense. Its objective is to serve the Center for New Industries and Technologies or CNIT, but this stop is then considered temporary and is only open during events. The final station was only opened in 1968 with the aim of serving the business district which has been booming since the early 1960s.

The line is divided into two parts for the power supply, a situation which stems from the history of the electrification of the national rail network and which requires the use of dual current equipment. The line from Paris Saint Lazare to Versailles Rive Droite, like the entire Paris Saint Lazare network, is electrified at 25 kV AC single phase. The line from Paris Montparnasse to Brest is electrified in 1.5 kV DC to Le Mans, included. A separation section is located on the Viroflay connection.

Line U is a line operated by the SNCF, from La Défense to La Verrière, which operates from 5 am to midnight, using sixteen Z 8800 trains. These trains use the Viroflay connection which was, at this time. occasion, open to commercial traffic, in order to connect the extreme terminals in 43 minutes. In addition, during the week, the line provides 89 daily departures. It does not work during the special night service set up on the occasion of important events such as the Music Festival and New Year's Eve, between 1 a. m. and 5 a. m.

A study, published in the newspaper 20 minutes presented this link as the penultimate of Île de France in terms of respect for timetables, because it is a transverse link directly influenced by traffic from Montparnasse and Saint Lazare networks and to be part of saturated traffic between La Défense and Saint Cloud, and between Versailles Chantiers and Saint Quentin en Yvelines.

Currently, 22 in number, the Z 8800s are coupled in pairs (UM2) during peak hours, in order to be able to double the capacity. Since July 2015, four Z 8800 trainsets coming from the RER C have joined the staff of line U (i. e. 24 trainsets). All the trains on this U line have the possibility of traveling on the N line (in particular to carry out the SOPI POSI mission trains), the equipment being provided with the plans of the two lines.

Line U rolling stock is maintained in the Trappes workshop, in Yvelines. In March 2005, a new equipment maintenance workshop opened along the tracks of the Trappes yard in Yvelines, replacing an existing workshop, at a cost of close to twelve million euros, entirely financed by SNCF. It is equipped with three tracks (two electrified and one non electrified) with an inspection pit, one of which has a switchable 1,500/25,000 volts catenary. Elevating cradles allow work at height. It also takes care of the maintenance of the twenty Z 5600 6 cars trainsets “Evolys” ,on line C of the RER and around sixty Corail cars. It also provides level 3 maintenance of TER 2N Center and Normandy. In addition, it has nearby a washing machine, a pit tower and a preparation site for cleaning and small maintenance operations.

At the start of 2017, according to SNCF estimates, the number of passengers going up daily in the line's stations was 52,000 on a basic working day (Tuesday or Thursday), 16,000 on Saturday and 10,000 on Sunday.