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Origin and history

The viaduct of Morez, located in the commune of Hauts de Biel (formerly Morez) in Burgundy-Franche-Comté, is part of a set of six viaducts and three tunnels built to connect the stations of Morbier and Morez, distant from 1,500 m in flight d'oiseau but separated by a 125 m elevation. This ambitious project, carried out at the beginning of the 20th century, aimed to create a railway link adapted to the topographical constraints of the Jura massif, with a maximum gradient of 3%. The viaduct of Morez, specifically, spans the valley of the Évalude at 40 m high and stands out for its nine arches of 20 m open, designed in local limestone rubble and Villebois (Ain) size stones.

Inaugurated in 1912 as part of the Morez-Saint-Claude section, this viaduct is the work of engineer Paul Séjourné, major figure of the bridges and carriageways of the PLM (Paris-Lyon-Mediterranean). Its construction, from 1909 to 1911, used an innovative technique of successive blank rollers per section to limit costs and structural disorders. Stayed also incorporated elegative vaults in the eardrums, although he criticized the aesthetics a posteriori. The viaduct, registered with the Historical Monuments in 1984, symbolizes the technical audacity of mountain railway infrastructure in the early twentieth century.

The railway context of the time was marked by the desire to open up the mountainous areas of the Jura, where the watch industry and local metallurgy (as in Morez) required efficient links. The six viaducts and three tunnels on the line, including the Crottes on a cliff, illustrate this adaptation to steep reliefs. The station of Morez, located at 736 m above sea level, became a strategic node between the valleys, despite the challenges posed by geography. The Morez viaduct, with its cast iron railings and reinforced concrete batteries, remains an emblematic testimony of this era of railway innovation.

The materials used, such as local and Villebois limestone rubble, or the rails integrated into the foundations, reflect a logic of economy and sustainability. The viaduct, 238 m long and 4.68 m wide, fits into a 250 m radius curve with a downhill slope of 4 mm/m, technical characteristics adapted to line constraints. His inscription in the title of Historical Monuments in 1984 highlights his heritage value, both for his architecture and for his role in the history of Jurassian transport.

The railway complex, including the viaducts of Morbier, Crottes, Romand, Évalude and the Source, as well as the tunnels of Crottes, Frasses and Pasture, forms a coherent system designed by Moron engineers (Ponts and Chaussées) and Moris (PLM). These works, which were put into operation between 1900 and 1912, reduced travel times and boosted the local economy, while integrating into the Jura landscape. Today, they are a remarkable industrial and technical heritage, witness to the ingenuity of the builders of the time.

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