It's one of those things that fans have debated. The general consensus is that they've reached a point, psychologically, where zombies have become part of the scenery. They're an inescapable part of the world. They see a zombie by the side of the road and it just doesn't register, any more than seeing a bird or wild animal near the road. Earlier, they might have panicked or stopped the car to get out and shoot it. Now, they don't even pay attention. Zombies are just there.
I interpreted it like [from shanes point of view] the walker is by himself just wondering around...
shane is also alone [rick doesn't listen to him, lori doesn't want him and the group follow rick] and shane realizes he is just wondering around doing ricks stupid missions...
so in that sense [in shanes head] the walker and him are one in the same...
I think it shows the change in them. Before they would always kill it immediately and panic but now it's showing you that they realize that there are walkers out there and they aren't worried about just one anymore.
In the 10'th episode of the second series I think it's called 18 Miles Out Shane and Rick take that kid away from the farm and plan to leave him in the middle of nowhere...
When they're in the car Shane spots a walker in a field walking towards the road and quite a long scene shows him looking at the walker, but why is he looking at it like that, and why does it show him looking at it once on the way and again on the way back?
