Paris Métro Line 10: Construction and Operation

Paris Métro Line 10 emerged from proposals for an inner ring in the city center. Before the First World War, planners envisaged incorporating Line 8 and a new southwestern branch into that ring. Later construction shifted toward supplementing transport on the Left Bank. On 30 December 1923, the service actually opened as Line 10 covered only the 2.85-kilometer section from Invalides to Croix-Rouge.

This section connected the surroundings of Invalides with the Saint-Germain district. New construction and tracks transferred from other lines subsequently extended its service area, turning the short route into a corridor across the Left Bank.

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Line 10 entered the existing network operated by the Compagnie du chemin de fer métropolitain de Paris, or CMP. Under the construction arrangements of the period, the City of Paris or the Seine department provided infrastructure such as tunnels and station shells. The concessionary company laid tracks, installed electrical equipment and built station entrances. Structural dimensions and engineering principles established for the early network by Fulgence Bienvenüe also provided the basis for additions after the war.

Once civil works were complete, crews installed entrances, power supply and operating equipment before the operator organized train service. Municipal and company responsibilities joined at these stages, turning underground structures into facilities for daily use.

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By the time Line 10 was built, Paris had developed underground construction methods suited to narrow streets. Ordinary routes ran at relatively shallow depths, but crossings with existing lines required changes to the vertical alignment. A typical two-track tunnel used an arched masonry and concrete structure with an internal width of about 7.10 meters. The standard length of an ordinary station with side platforms was 75 meters. Depth and cross-section at crossings varied with existing tracks and ground conditions.

Lucien Lupiac, responsible for new works, explained that small timber-supported headings remained widely used for ordinary tunnels until 1937. Workers completed the crown first, then underpinned the side walls and excavated the lower ground before constructing the invert. Staged excavation, support and masonry allowed the route to advance beneath city streets. Within an already built network, keeping the ground and existing structures stable was particularly important.

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After the first opening, the line reached Mabillon on 10 March 1925 and Odéon on 14 February 1926. Service expanded in short stages. Each new terminus changed the neighborhoods reached by trains and increased opportunities to connect with the existing network.

The service depended on continuing coordination between station and train staff. The station workforce included station supervisors, ticket sellers and ticket inspectors. Supervisors also handled train delays, lighting or power failures, and passed information by telephone. Train-controlled gates, introduced progressively from 1921, enabled some stations to concentrate ticket inspection for both platforms. Equipment changes directly affected the organization of work.

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On 15 February 1930, Line 10 trains continued from Odéon to Place d’Italie, and on 7 March they reached Porte de Choisy. Line 10 temporarily served the southern section while Line 7’s river crossing was completed.

On 26 April 1931, Line 7 opened its cross-river section and took over the southern route. Line 10 instead used a new section east of Maubert–Mutualité to reach Jussieu. An urban railway could provide transport using available connections and then reassign routes as neighboring projects were completed. Operating numbers and section assignments changed with the development of the network.

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In July 1937, Lines 8, 10 and the former Line 14 were reorganized together. Line 8 turned toward Balard, and its former western section toward Porte d’Auteuil passed to Line 10. Line 10’s old branch toward Invalides became part of the former Line 14. On 27 July, Line 10 briefly operated as two sections, Porte d’Auteuil–La Motte-Picquet–Grenelle and Duroc–Jussieu. On 29 July, a new connecting section joined them into a Porte d’Auteuil–Jussieu route.

On 12 July 1939, the eastern end reached Orléans–Austerlitz station, improving links between Left Bank neighborhoods and a mainline railway terminal. The western end later extended into Boulogne in separate stages in 1980 and 1981. Line 10’s eventual transport pattern resulted from successive construction and reorganization of existing routes. Its 1923 opening was the first passenger-service stage in that process.

References: [1] [3]