Driving the steep D308 to Col de la Ramaz: The challenge of Tunnel de Sommand
Col de la Ramaz is a high mountain pass at an elevation of 1,619m (5,311ft) above sea level, located in the Haute-Savoie department of France. This pass is a classic of the French Alps, connecting the Giffre valley with the Praz de Lys ski area, and is world-renowned for its frequent inclusion in the Tour de France.
The road is famous for its dramatic scenery, but also for its technical sections. The most iconic point of the climb is the Tunnel de Sommand. This tunnel was built to bypass a terrifyingly narrow stretch of road that hung off the edge of a sheer limestone cliff. Even today, the tunnel remains narrow, curved, and poorly lit, with openings in the rock that offer dizzying glimpses of the drop below. It’s a true "balcony road" experience that requires total concentration.
| Road facts: Col de la Ramaz | |
|---|---|
| Location | Haute-Savoie, Alps (France) |
| Elevation | 1,619 m (5,311 ft) |
| Road Name | D308 |
| Length | 23 km (14.3 miles) |
| Max Gradient | 12% |
| Key Feature | Tunnel de Sommand |
How difficult is the climb to Col de la Ramaz?
The ascent from Mieussy is 14 km long and is considered the "classic" side of the pass. The road, the D17/D308, hits you with a brutal section as you approach the Tunnel de Sommand, where the gradient stays consistently around 10-12% for several kilometers. This is a massive test for your vehicle’s cooling system and brakes, especially if you are driving a heavy campervan or towing a trailer.
Inside the Tunnel de Sommand, the road is narrow and the pavement can be damp even in summer. You need to be extremely careful with cyclists, as they are very common on this Tour de France route and can be hard to spot in the sudden darkness of the tunnel. Once you clear this section, the road opens up into the beautiful Sommand plateau, providing a brief relief before the final push to the summit.
What are the views from the summit?
Reaching the 1,619m summit provides one of the best rewards in the Savoie region: an exceptional view of the Mont Blanc range. On a clear day, the snow-capped peaks feel incredibly close. The pass is 23 km long in total, running west to east and eventually connecting with the D902 Road, which is part of the legendary Route des Grandes Alpes.
Because of the altitude and its role in serving the Praz de Lys ski resort, the road is closed during winter storms and heavy snow. The best time to drive it is from late May to October. If you’re coming down towards Mieussy, watch your speed; the continuous steep ramps and the tight turns before the tunnel can quickly overheat your brakes if you don't use the engine to slow down. It’s a legendary road that perfectly balances alpine beauty with technical driving.