Road to Survival: Fortress of the Apocalypse

The truck is the only thing Daniel Walker owns outright. He drove it for years to pay for the family that adopted him, spent everything he had on them, and when the red rain came and the infected spread through the city, they shut the door on him and let him die outside it. He wakes up in the cab again, six hours before the rain. The Apocalypse Squad System comes with him, and the first thing it lets him do is work on the truck. He reinforces the body, strips out what is useless, and turns the trailer into somewhere people can sleep behind steel. Fuel, water, ammunition, medicine, all of it goes in while the shops are still open and the roads are still passable. Then he starts picking up passengers. Fighters, people with skills worth the space, recruited into the squad one at a time as the truck moves. Supplies get taken from places already emptied of the living. The infected do not stay the same, and the ones he meets later are faster and harder to put down than the ones on the first day. There is an armed group tracking the truck as well, less interested in the vehicle than in what it is carrying and where it is going. His old family survives longer than he expected. They find the truck on the road and they want in, and this time the door being knocked on is his.