As long as their driveway material is under about 2inches you could glyphosate the edges of the driveway & after a nice rain storm you'd come back with a rear blade & roll in the side material back into the center of the driveway. Gravel/dirt roads need a 4% crown for proper drainage or you're just asking for potholes. I'd also recommend that the driveway is at least six inches above the water table or above the water in the ditch so it doesn't get soggy. The max width of a driveway should be 12ft for single lane & 20ft for dual lanes.