In a midst of a disaster, you need to be tough. But, in an apocalypse situation, you need to be tougher. There will be death in every corner of the street because the zombies will always be there. You need to get out of the city and flee for your life. You need a truck that can drive you out of the city and that is what you will need to get out of the city alive. A safe zone is what you need and it isn't in the city, where there will be lots of undead haunting you down.
Drive the truck as fast as you can till you reach the finish line. Well, there is no way that you can do that in an instant. The game will reward you some cash based on the distance you traveled and some stunts you did. Use it to upgrade and possible buy a new truck to get out of the city. However, you will need some time to finally get out of the city as you will need cash to do it. You need to upgrade your truck little by little till you have enough to buy a new truck and upgrade it too. That is the only way to finish the game.