Paris Métro Line 9

Line 9
An MF 01 stock train at Billancourt
Overview
System	Paris Métro
Locale	3 communes
Termini	Pont de Sèvres Mairie de Montreuil
Connecting lines
Stations	37
Ridership	119,885,878 (2010) (avg. per year) 3rd/16 (2010)
Operation
Opened	1922
Operator(s)	RATP
Conduction system	Conductor
Rolling stock	MF 01 (67 trains in revenue service as of 17 November 2016.
Technical
Line length	19.6 km (12.2 mi)
Track gauge	1,435 mm (4 ft 8 1⁄2 in) standard gauge
Electrification	750 V DC third rail

Paris Métro Line 9 is one of 16 lines of the Paris Métro. The line links Pont de Sèvres in Boulogne in the west with Montreuil in the east via the city center of Paris, creating a parabola type shape to its route. It is the third busiest line on the network.

Line 9 interchanges with all of the 13 other main Métro lines, except for one (Line 12), not including 3bis and 7bis according to the RATP maps. There is, however, a connection to Line 12 via the underground passageway from Saint-Augustin to Saint-Lazare. This connection is not advertised as it is not normally useful unless one is traveling between the southern portion of the 8th arrondissement and Levallois-Perret.

Line 9 was originally envisioned as a branch of Line 2 Sud (now known as Line 6) between Porte de Saint-Cloud and Trocadero. However, it was concluded by the CMP to combine this segment with a proposed segment that was to be built towards Opera, and thus Line 9 is created. The first section between Trocadero and Exelmans opened on 8 November 1922.

Construction of the original sections (as well as the extension towards République) proved to be difficult due to public opposition in the various arrondissements as well as unstable soil above the tunnels. Public support for the line's construction was greatly difficult due in part to proposed sections that various entities saw as impossible to build and operate under government regulations at the time. In addition, unstable soil led to the collapse of several sections of tunnel being constructed. The double-decker tunnel, which is located between stations Richelieu - Drouot and République (and carries Line 9 on the lower level, while Line 8 is situated on the upper level) was especially problematic due to unstable ground at Grand Boulevards. As a result, this particular section had to be reinforced by central piers.