Changes

You can SHOULD take the RER B to ''Massy-Palaiseau''. From there you will be able to follow motoway signs for the A10. In order to get out of the several rings of highways surrounding Paris it could be really useful to start hitching from this place, especially since you get directly on the A10, after all the branch-offs. There are two options: take a bus from the massive transport lot beside ''Massy-Palaiseau'' station or walk down a motorway ramp nearby! I would strongly advise the ramp option!

Go down the ''Avenue Carnot'' along the ''Massy-Palaiseau'' railway towards the ''autoroute''. After a while there you will see a long stretch of a road with lots of space for cars. Keep going and you will reach a roundabout. If you keep following this road, you will reach a motorway exit underneath a bridge. It would be a good idea to use a sign with "Chartres" as this will make sure to get a ride at least to the first ''barrière de péage'' (30+ km) at St.Arnault or to the Briis-sous-Forges service station 5KM down the road.