Generally, AP centers in a lane. It would be desirable in some lanes to shift off the center. For example, in the fast lane, with a barrier on the left, it may be smart to move to the left of the lane by a foot or so to give more room between you and vehicles in the adjacent lane.
In addition, when in a center lane, perhaps adjust depending on vehicles around you, to put a bit more space between you and an adjacent vehicle.
a) When there are two lanes in one direction, and there is a large or oversized vehicle/truck, in the lane beside you. In this case, the car knows this and should keep the car closer to the other side of your lane. This way, if the truck does move into your lane, you already have some extra safety margin and hence time to react. This is how a smart human driver would drive. That is, if there is a truck on my right, the car should position itself in my lane, say 1 foot away from the left-hand lane line, leaving say 3 feet to the car’s right-hand lane line (further away from the truck). There have been many cases in my car when the car will try and stay in the middle of the lane (but this fluctuates) and at times goes very close (within 1-2 feet) of a truck in the lane next to me. I always keep away from trucks as it doesn’t take much for them to move about on a windy day, and into your lane suddenly.
b) When you are going around a slight left corner or bend in the road, it would save a bit of energy to preference (slightly) the left-hand side of the lane.
c) When you are driving in one lane and the other lane is on-coming traffic, it is safer to preference the other side of your lane so that there is again more margin for error if the on-coming driver loses concentration. We all sometimes see on-coming cars veer into our lanes slightly, and by preferencing the edge of our lane (further way) we have more time to react/move over or honk the horn, etc. if required.