This is a short series of gamebooks by Lone Wolf Gamebooks author Joe Dever, inspired by Mad Max and The Grapes of Wrath. In Dever's own words, "an exodus story and a post-apocalypse story combined."
From the Project Aon website:
The four-book Freeway Warrior series was published in the UK between 1988-89 and follows the adventures of Cal Phoenix, a young survivor of a terrible attack. Set in a post-Apocalyptic United States in the year 2020, Cal and his surrogate family—Dallas Colony 1—must travel across the desolated mid-west in order to escape from the lawless biker gangs and the evil Mad Dog Michigan.