Movie trailers for I Am Legend

So was that ever explained? The bridge thing? Seems like a fairly major oversight. Didn't they come in by boat or something? You'd think if you had a kickass Shelby and the roads were empty, you'd find any way out of the city pretty damn fast.

Apparently the deleted scene ending - the movie's original ending - was removed after a negative focus group response. I'd like to find whichever cotton-headed ninny muggins were responsible for that decision and beat them to death with shovels.