Construction and layout

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The SGLM was chartered to haul coal from "La Mure". The Matheysin plateau is located at an elevation of 1000 meters, with rugged terrain. Only a narrow gauge railway could suit the harsh constraints of the steep grades (700 meters in 30 km).

It was at the end of summer, 1882, that the construction work began under the direction of "Ponts et Chaussées" chief engineer Rivoire-Vicat. Even though the builders faced tremendous challenges, the construction of the engineering masterpieces was completed in 1885, before the completion of the rolling stock. From PK 8 to PK 15, rock blasting occurred in an unsual manner--103 canon rounds were fired Mai 23, 1885 at the smooth near vertical cliffs of the tumultuous Drac River canyon (today tammed by a dam) from the opposite wall of the gorge.

Starting from the station of Saint Georges de Commiers (elev. 315 m), the line eases out northward and succesively passes through 18 tunnels and acrosss 9 major viaducts. The track clings to the side of the Drac canyon, 300 meters above the river level, itself higher than before due to construction in 1962 of a large hydroelectric dam. The highest point of the line reaches 1071 meters above sea level and is found inside a 1000 meter tunnel. The end of the line is now at La Mure-Ville (elev. 881 m). Fully 15% of the 30 km journey , or 4257 meters, is inside tunnels.

The SLGM can undoubtedly be called a moutain railway line. 51% of the line is curves. The minimum radius of 100 meters is encountered 65 times, almost half of the line's 133 numbered curves. The largest curve radius is 600 meters and the grade of the line is a continuous 2.75%. While the railway line is 30096.17 meters in length, a direct line between the beginning and end of the line is only 16 km in length.



The viaducts and major bridges of the St Georges-La Mure section
Names PK length heigth number of arches span (m)
Pivon's viaduct 11.3 59 10 3 12
Clapisse's viaduct 13.5 55 13 3 12
Rivoire's viaduct 14.4 55 12 4 10
Vaulx viaduct 17.0 170 34 9 10
Loulla's viaduct (downward) 18.1 85 22 3 10
Loulla's viaduct (upward) 19.6 110 37 6 10
Valley's bridge 10.9 44 7 1 15
Brondes's bridge 14.0 34 10 1 25
Rivoire's bridge 14.3 34 22 1 25


Among all construction works, let's remark the twin Loulla's viaducts, superposed on Loullas's stream, and the Vaulx's river viaduct. On the Mure-Gap route section, which is now no more in service. The Roizonne's viaduct was in 1920 the highest one in all Europe (120 m).



The 18 tunnels of the St Georges-La Mure section
Tunnels names PK (head) Lenght (m) Grade (cm) Curvature (m)
Ravinson 0,8 383,15 24,4 100
Mollard 4,8 89,02 25,3 100
Pré-Béron 5,45 254,73 22,5 100
Commiers 6,5 129,46 22,5 100
Bessat 7,2 88,74 22,5 100
Pierre Villaire 9,25 88,53 22,5 100
Ripeaux 9,8 438,23 22,5 100
Challanches I 11,7 152,80 24,24 100
Challanches II 11,95 298,60 24,24 100
Serguignier 13,1 309,51 25,0 200
Brondes 13,5 401,47 25,0 150
Rivoire 14,4 50,43 26,8 straight
Gravaison 14,7 85,42 26,8 100
Raux 15,65 29,61 27,5 straight
Tuilerie 18,95 135,84 25,0 100
Loulla 19,6 36,06 25,0 straight
Combefolle 22,0 214,13 22,5 100
La Festinière 23,9 1071,035 22,6 straight


The buildings along the line are typical from P.L.M. (Paris Lyon Méditérannée). Far from beeing overlooked in size and quality, they are fitted with "marquises" and platforms are bordered with carved stones. The principal train stations of the line are Saint Georges de Commiers (shared between SGLM and SNCF), Notre-dame de Commiers, La Motte-les-bains, La Motte d'Aveillans and La Mure-Ville.



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