From the introduction:
In most Final Fantasy games, gaining access to a vehicle (normally an airship) is an important step in the game. It allows the player to go to places where they were previously unable to go on by foot, chocobo, or, if it was available in the game, a boat. Normally a vehicle doesn’t really do much in the Final Fantasy games else.
But this Vehicle Manual does things differently.
Inspired by games such as Skies of Arcadia and Xenogears, the Vehicle Manual allows players or gamemasters to construct nearly any type of vehiclebe it a tank, mecha, submarine, airship, or spaceshipfor the Returner Final Fantasy RPG system. These vehicles can then be used to fight with other similar vehicles, which is what this sourcebook was created for. The Vehicle Manual includes comprehensive rules for vehicle creation, combat, equipment, enemy vehicles, and even gamemaster advice for campaigns where the game centers on the use of vehicles nearly as much as it does around the characters themselves.