For those staying in Paris before PBP, here is a bike route from the Arc de Triomphe to the start in Saint Quentin-en-Yvelines.
The route is easy to follow, yet it doesn’t see a lot of traffic. There is a nice bike path after you ride past the Chateau of Versailles. The only tricky turn is toward the end, the left onto the D129 “Rue Emile Zola,” which is a small street on a steep hill. The total distance is just under 25 km: A perfect warm-up for the big ride.