Facing and Firing Arcs

Unlike with characters, when dealing with vehicles, the vehicle's facing (the direction it's pointing) is important. Facing indicates the direction in which the vehicle is traveling (assuming it's not moving in reverse). It can also determine which weapons aboard the vehicle can be brought to bear on a target.
A weapon built into a vehicle can by mounted to fire in one of four directions-forward, aft (rear), right, or left-or be built into a partial or full turret. A partial turret lets a weapon fire into three adjacent fire arcs (such as forward, left, and right), while a full turret lets it fire in any direction. For vehicles with weapons, a weapon's arc of fire is given in the vehicle's description.