The only improvement I would make would be to make it possible to hold more than 300 food. You never NEED more than 300, but warehouse/malls/Allmarts should definitely hold extra food.
Also, I loved the char names. John Stuart? Presh.
I enjoyed the game. 4/5, because there are glitches, like mines hitting the car in front and then appearing again. Also, make the barricades a little longer so the cars don't get behind them.
If you get behind a barricade, just keep going. The computer will reset you faster than it would take to go back around it.