These rules use two scales. If the encounter involves both vehicles and characters on foot, use character scale. If the scene involves only vehicles, and they’re likely to move at much higher speeds than characters or creatures on foot, use chase scale.
Character Scale: Character scale is identical to the standard movement scale: It’s carried out on a grid in which each square equals 5 feet. In character scale, most vehicles are large enough to occupy multiple squares on the map grid. How many squares a vehicle occupies is specified in the vehicle’s description.
When moving a vehicle, count the squares from the vehicle’s rear. When turning, pivot the vehicle on the rear square toward which it is turning. When firing weapons, count squares from the location of the weapon. In character scale, more than one ground vehicle cannot occupy the same square.
Chase Scale: In chase scale, each square of the grid represents 50 feet.
In chase scale, most commonly encountered vehicles occupy only one square. (Some especially large vehicles, such as ships or jumbo jets, might occupy more than one square.) More than one vehicle can occupy the same square. Vehicles in the same square are considered to be 20 feet apart for the purposes of determining range for attacks.