Neville: What the hell are you doing out here, Fred? Fred, if you're real, you better tell me right now!
Neville: Nothin' happened the way it was supposed to happen.
Neville: God didn't do this. We did!
Neville: My name is Robert Neville. I am a survivor living in New York City. I am broadcasting on all AM frequencies. I will be at the South Street Seaport everyday at mid-day, when the sun is highest in the sky. If you are out there... If anyone is out there... I can provide food, I can provide shelter, I can provide security. If there's anybody out there... Anybody... Please. You are not alone.
Answer: In the alternative ending Dr.Neville, Anna and Ethan are seen driving a car over a bridge that wasn't destroyed. The army would need to leave a entry/exit point, but it would have been heavily guarded until everyone died.