In I Am Legend, the clip I was watching seemed to display an involvement of the audience. In the car shots, you seemed as if you were in the car with Will Smith and his dog; either in the side or back seat. It gives you his point of view of how he sees the city and what he sees.The effect of these types of camera shot is the film feels more real, and therefore more enjoyable.
Another theme of this scene is that although all the human race seems to be wiped out, it doesn't seem as though the world has suffered majorly, as the sun seems to be shining and the nature of all the birds are singing happily which gives the impression that even in New York City - a massively populated city doesn't need people around to work it.
As Will Smith drives around New York he moves past different posters and particularly emphasized on one that said 'God still loves her' which could potentially mean two different things - that they (human race) have committed an awful crime that cannot be undone and are very blamed; or that something awful had happened to the human race and no matter what he will still love you.
The props and setting used in their scene also give the theme of danger. All the guns, red car, bollards/cones on the road and deers running across the road have connotations of danger and horror.