Scenario: say you FINALLY go fulltime driving after you use to pass it up when they called. You have been there for 10 years. Now someone else has been there 4 years but they went fulltime the first chance they got. So now they have more driving senority then you in terms of vacations, getting days off, etc. But u have been at the building 6 years longer than them.
Now say something happens where they lay off mass drivers. New competition, work automation, whatever. I know drivers get sent back to the building if they are laid off for an excessive amount of time. But who is completely out of work and on the streets first if you are both drivers?