Every vehicle has a top speed, included in its statistics on Table: Vehicles. A vehicle cannot move more squares than its top speed. This means that some vehicles cannot move at all-out speed, or even highway speed.
Count squares for vehicles just as for characters. Vehicles can move diagonally; remember that when moving diagonally, every second square costs two squares’ worth of movement. Unlike with moving characters, a vehicle’s facing is important; unless it changes direction, a vehicle always moves in the direction of its facing (or in the opposite direction, if it’s moving in reverse).