I’m not sure how I’ve missed this route for so long. I’ve been to St Jean-en-Royans several times, and despite my regular poring over maps I’d never seen the option to get back up to the Vercors plateau via the Tunnel du Pionnier. At last I’ve ridden it, and I can report that it is a most spectacular route.
From St Jean, taking the road up the hill towards Combe Laval, the D131 is signposted to Lente and Font d’Urle, and a left turn at Col de la Croix after 10km takes you onto the D331.
The two roads and cols have completely different characters: the D131 meanders upwards towards a very visible col ahead; the D331 takes a hairpin route up the side of the valley and then dives through the short but splendid Tunnel du Pionnier, which pierces the seemingly impregnable rock face which has dominated the ascent.
But be prepared for a long haul: the 30km from St Jean to Font d’Urle is 1200m of ascent, and is likely to take you a couple of arduous hours or more. On the plus side, you’ll see very few other bikes or cars, even at the height of the holiday season, as it seems that not many other people know about this hidden gem either.