Help! Can't remember a movie title??

So I remember when I was younger (I am 18 now), I saw a movie with my dad that I want to see again. The only parts I can remember is that they wanted to stay away from the air outside. I BELIVE they were at a diner or something? Then some people run into a car and end up driving into a tree. I also remember these people going to a house, and in the back yard there was a shed-like building with an old infected person in it. Please help me figure out what movie this is?? I've been so confused.