I drove from the Galibier pass road up to 2137 m (small unpaved road goind in direction to "seuil des rochilles". though having a 4WD, I decided to stop at 2137 (about 2-3 km away from main Galibier road) practically at the foot of the grand Galibier north face (small glacier with a 400m couloir at 45° I soloed a long time ago). I spent the night at my car, leaving in direction of col des rochilles, then to col des cerces. Right from the col des cerces at 2574m, a small path (some signs in green and red from time to time) leads to the top, with a neve crossing - a long time ago it used to be small glacier-(if hard snow or ice, bring crampons and ice axe, rope as well). the couloir (horizontal) crossing is not difficult and slightly exposed (35 degrees or so). I reached the summit in 2h30, then went back to col des cerces and lac des cerces, then to the car (approx 1h30 going down). nice view from the top.
Be careful all the area is located in a military zone where a few days in the year, access might be restricted (this rarely happens though).
From Chalets de Laval (Val Clarée)