The SR uses 16 unpaved passes listed by Club des Cent Cols, and 5 mixed passes (one side is tarred, the other not), to which we can add 4 other passes, which are not listed (3 unpaved, and 1 mixed), plus the climb of Montagne de Chabre (mixed). See details in the table below. The unpaved roads are cyclable, without requiring special technical knowledge. Only two difficulties need to be overcome on foot (0.3 km at the Areste ravine, and 1.5 km after Ainac). Sometimes, the steepness of the slope can make you push the bike.
The dirt roads are mainly forest roads of medium altitude (the SR culminates modestly at Col d'Arron, at 1,445 m altitude). The nature of the ground varies (ocher, brown, black earth, more or less stony, depending on the location). The ground is mostly limestone, rather hard, although some dirt roads still get slippery and muddy when it rains. Find below two links to photos of the SRDE dirt roads.
All of these dirt roads have been carefully selected. The idea was not just to ride on a dirt road for fun, but to take you to secret and remarkable places. Villages and hamlets perched in the mountains, where the tar stops; ruins; farms; passes better known to hikers than to cycle tourists; and quite simply, the great calm of nature. Ride for miles without encountering a motor vehicle, yes, it is possible (unlike the famous dirt roads - Assietta, Parpaillon, Strada del Sale - the dirt roads of the SR du Désert are not among the highlights selected by motorized off-road vehicle drivers).
The SR du Désert lives up to its name since even the 407 km of asphalt, between the dirt roads, do not offer many refueling or sleeping opportunities (unless you deviate from the course) . Buis-les-Baronnies is the only medium-sized town that is crossed by the route. However, finding water is not a problem. Autonomy and resourcefulness will be your allies in this adventure !