You have not yet joined the evacuation zone during the first part, and so you need to hit the road again aboard three new vehicles: a fire truck, a truck tractor or a military armored vehicle.
Drive as far as possible, crushing mercilessly all zombies in your path, then use the money earned to upgrade your vehicle.
Huge success of Not Doppler, Earn to Die 2012 part 2 is the highly anticipated sequel to one of the best games of the genre.
See also:
Earn to Die 2012: Part 1
Earn to Die 2: Exodus
