We broke down on an autoroute our way home this year and phoned our breakdown company to be told that only the police had the authority to deal with breakdowns on a motorway and that we had to walk to the nearest services or ring them from one of the phones by the roadside. Once we had done that we could then phone our breakdown company back. Although, as we were stood by the van a man stopped in a road works truck and we asked him if he would phone the police he said yes and went back to his truck. A breakdown truck then turned up and we phoned our breakdown company back, he spoke to the man in French and then said that it was OK to fix the van. I'm sure if you phone your breakdown company before you go then they will tell you what you have to do, and on which roads. Hope this helps.