Is there such a position for someone like me that is capable to relieve truckdriver's out of hours service, and drive for that individual in exchange of my hours?
You would have to hired on by the truck company, which isn't going to happen if you and the out of hours driver are in a truckstop someplace miles from the home terminal. If it was an O/O, would he be aware that you were available, and would he trust you to drive HIS truck, a perfect stranger ? Not likely.