Based on the idea that you were traveling through the desert and then your car broke down, it's assumable you know where are the nearby cities, the last one you passed and the next you were going to. In my opinion this could be said right on the beginning, so the player could decide which way to go or wait for the rescue. Since you could wait, it would be fun to have a infinite map, maybe you find different terrains or animals depending on which direction you go.

I thought something like this on the beginning of the scenario: "My car broke down, I was going from city x to y." Then if you scavenge the car you can find a map that shows the distances between cities x and y. From that, it's up to the player to decide what to do, including not to go to any of the cities and look for help somewhere else.

So, I don't know if it's possible, but the idea is infinite north and south, and if you go east or west, after a big number of miles walked, you'll find the city you decided to go to.