Line 4 (French pronunciation: ​[liɲᵊ katʁᵊ]) is one of the sixteen lines of the Paris Métro rapid transit system. Situated mostly within the boundaries of the City of Paris, it connects Porte de Clignancourt in the north and Mairie de Montrouge in the south, travelling across the heart of the city. Prior to 2013, when the southern terminus was changed from Porte d’Orléans to Mairie de Montrouge, the line was sometimes referred to as the Clignancourt – Orléans Line. At 12.1 km (7.5 mi) in length, it connects to all of the lines of the Métro apart from the 3bis and 7bis branch lines, as well as all of the RER express lines. Further, it is the second-busiest Métro line after Line 1, carrying over 154 million passengers in 2004.

This article may be expanded with text translated from the corresponding article in French. (April 2015)Click [show] for important translation instructions. View a machine-translated version of the French article. Machine translation like DeepL or Google Translate is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing French Wikipedia article at [[:fr:Ligne 4 du métro de Paris]]; see its history for attribution. You should also add the template {{Translated|fr|Ligne 4 du métro de Paris}} to the talk page. For more guidance, see Wikipedia:Translation.

Line 4
MP 89CC stock train arriving at Denfert-Rochereau.
Overview
Termini	Porte de Clignancourt Mairie de Montrouge
Connecting lines
Stations	27
Service
System	Paris Métro
Operator(s)	RATP
Rolling stock	MP 89CC (48 trains in operation as of 23 March 2013)[1] (4 trains in reserve as of 23 March 2013)
Ridership	171,000,000 (avg. per year) 2nd/16
History
Opened	1908
Technical
Line length	12.1 km (7.5 mi)
Track gauge	1,435 mm ( 4 ft 8+1⁄2 in) standard gauge between roll ways
Electrification	750 VDC, guide bars on either side of the track
Conduction system	Conductor (PA)
Route map Legend proposed extension Saint-Ouen–Les Docks Mairie de Saint-Ouen   Michelet–Docteur Bauer proposed extension Saint-Ouen shops Porte de Clignancourt Simplon Marcadet–Poissonniers Château Rouge Barbès–Rochechouart to La Plaine–Stade de France to Stade de France–Saint-Denis Gare du Nord Gare de l’Est Château d’Eau Strasbourg–Saint-Denis Réaumur–Sébastopol Étienne Marcel Les Halles Châtelet–Les Halles (RER) Châtelet Seine Cité Seine Saint-Michel Saint-Michel–Notre-Dame (RER) Odéon Saint-Germain-des-Prés Saint-Sulpice Saint-Placide Montparnasse–Bienvenüe Vavin Raspail Denfert-Rochereau to Cité Universitaire Mouton-Duvernet Alésia Porte d’Orléans Mairie de Montrouge extension under construction extension under construction Barbara Bagneux-Lucie Aubrac  future This diagram: view talk edit

Line 4 was the first line to connect the Right and Left Banks of Paris via an underwater tunnel, built between 1905 and 1907. Line 4 long ran the oldest cars in service on the system, the MP 59, which used rubber tyres to dissipate the braking power through resistance. Those trains were withdrawn from service during the course of 2011 and 2012 after 45 years (with some being in service for 50 years). They were replaced by the MP 89 CC stock from Line 1 when the latter line was automatised. (From fr:Ligne 4 du métro de Paris).

In the first decade of the 21st century, Line 4 was extended for the first time since its initial construction, into the southern suburbs of Montrouge. It now serves the new southern terminus of Mairie de Montrouge. Construction of the extension began in 2008 and it opened to passengers on 23 March 2013 .[2] The line is now being retrofitted for full automation, with completion expected in the early 2020s.

. . . Paris Métro Line 4 . . .

• 21 April 1908: A first section of the line was inaugurated to the north of the Seine between Porte de Clignancourt and Châtelet.
• 30 October 1909: A second section of the line was inaugurated south of the Seine between Porte d’Orléans and Raspail.
• 9 January 1910: Both sections were linked by a new tunnel between Châtelet and Raspail. Line 4 was the first line crossing the Seine river underground.
• 1967: The rails were converted in order to cater for rubber-tired trains. The MP 59 rolling stock replaced the steel-wheeled Sprague-Thomson stock.
• 3 October 1977: The station Les Halles was rebuilt to interchange with the new RER network.
• 23 May 2011: Cascading of MP 59 to MP 89CC rolling stock began.
• 21 December 2012: The last MP 59 (#6021) was withdrawn after 45 years of service on Line 4.
• 23 March 2013: Station Mairie de Montrouge officially opened to passengers, marking the first extension of Line 4 since its inception.

Line 4, opened in 1908, was the last line of the original concession of the Compagnie du chemin de fer métropolitain de Paris and the first to cross the Seine underground (Line 5—now Line 6 at this point—crossed the river on the Passy bridge, later renamed the Pont de Bir-Hakeim in 1906). The route was the subject of lengthy discussions that delayed the start of construction of the tunnel. It was originally planned as a straight line under the Rue du Louvre, under the Seine in line with the street, under the Institut de France, along the Rue de Rennes and then the Boulevard Raspail to the Porte d’Orleans.

But as a result of the delay in beginning the extension of the Rue de Rennes as part of Haussmann’s plan to the Seine—which was never carried out—and the outcry from the academics who refused categorically to agree to the line passing under the Institut de France, the route was eventually changed to cross further east through the Place du Châtelet and the Île de la Cité.[3] The new route also has more coherence as a north–south route following the main traffic flows. A second modification of the route was also made: it was decided to make a temporary deviation via the major station of Gare Montparnasse to avoid a further delay in opening the line, which was eagerly awaited. This was made necessary by the delay in building the new Boulevard Raspail between Rue de Rennes and Boulevard du Montparnasse.[4] Once the Boulevard Raspail was completed, it was planned to take the shorter route and bypass the Gare Montparnasse. To the south of the Vavin station the tunnel provides for the final route along the Boulevard Raspail. But the value in serving three major mainline stations by the line later led to the abandonment of this proposal.[5]

. . . Paris Métro Line 4 . . .

. . . Paris Métro Line 4 . . .