The Walking Dead comic shows that in the future of the series (relative to where we are now) they are basically using horses all the time. By this time, they have learned to 'herd' zombie hordes effectively. They also use horse-drawn wagons for trade between towns. read more
I don't watch or read Walking Dead, but the United States currently uses more petrol than the entire rest of the world combined. In 2011, that was 134 billion gallons. Now, if a zombie apocalypse occurred, the number of people driving cars would drop dramatically. read more