Is the road to Col du Clergeon in the Jura Mountains too steep?
Col du Clergeon is a mountain pass sitting at an elevation of 979m (3,211ft) above sea level in the Auvergne-Rhône-Alpes region of France. Located on the boundary between the Haute-Savoie and Savoie departments, the road over the pass is a treacherous stretch of asphalt that defies its relatively low altitude. Known as the D55 on the Savoie side and the D231 in Haute-Savoie, this route is a favorite for local cyclists but a logistical headache for drivers due to its extreme narrowness and punishing gradients.
| Road facts: Col du Clergeon | |
|---|---|
| Location | Savoie / Haute-Savoie boundary (France) |
| Elevation | 979 m (3,211 ft) |
| Length | 19.9 km (12.3 miles) |
| Max Gradient | 10.5% (Average for 2 km) |
| Surface | Paved (Narrow / Rough) |
How long is the road through Col du Clergeon?
The road through the pass is 19.9 km (12.3 miles) long, running west-east from Ruffieux to Moye. While the entire route is paved, the asphalt is often in poor condition, with frost heaves and cracks that make for a bumpy journey. Over this distance, the total elevation gain is +796 meters. It is a classic Jura Mountain road where the forest closes in on the track, leaving very little room for two vehicles to pass each other. If you meet a van or a farm vehicle coming the other way, you will likely have to back up until you find a wider pocket in the road.
How steep are the ramps on Col du Clergeon?
The average gradient of the climb is 7.3%, but this figure hides the true brutality of the pass. The middle section of the road is where the real challenge lies: two consecutive kilometers average a punishing 10.5%, with shorter stretches hitting even higher percentages. For a standard car, these ramps require maintaining a low gear to prevent the engine from lugging. If you are driving a heavily loaded vehicle, the heat buildup in the cooling system can become an issue, especially during the humid summer months in the Rhône-Alpes.
What are the hazards of driving the D55 and D231?
The main hazard on Col du Clergeon is the lack of width. As seen in the higher plateaus, the road often shrinks to a single lane with no shoulders, only grass and steep embankments. In autumn, the asphalt is frequently covered in wet leaves and mud from agricultural activity, making the 10.5% ramps as slippery as ice. The descent toward Moye is equally technical; the constant need to brake on narrow, winding sections can lead to brake fade if you don't utilize engine braking. It is a road that demands full concentration and a slow, controlled pace to manage the blind corners through the woods.
Is Col du Clergeon open in winter?
While the pass is not among the highest in the Alps, its location in the Jura Mountains means it is subject to heavy snowfall and black ice. The D55 and D231 are secondary roads and are not always the first to be cleared by snowplows. During the winter months, the steep gradients make traction nearly impossible for standard 2WD vehicles without high-quality winter tires or chains. The road can become a "dead end" very quickly if a sudden storm hits the boundary between Savoie and Haute-Savoie, leaving drivers stranded on a narrow ledge with no room to turn around.