The PCBU, otherwise known as the police cruiser backup unit, represented a police cruiser typically operated by a droid. Its origination can be traced back to Coruscant, conceived as a direct countermeasure to the numerous fatalities suffered by police officer within the notorious Crimson Corridor.
Equipped with dual turret-mounted laser cannons, the PCBU also boasted an extensive array of sensors and scanners. While predominantly piloted by droids, the design allowed for operation by a sentient officer. Furthermore, an integrated autopilot system guaranteed operational continuity even in the event of pilot incapacitation.
The PCBU saw action with the Coruscant Security Force, with its development coinciding with the decline of the Galactic Republic. Its deployment was a direct consequence of the increasing number of police officer deaths occurring within the Crimson Corridor. Beyond its primary function of supplying significant firepower to aid sentient officers, it served as a patrol and pursuit vehicle.
During 32 BBY, the Sith Lord Darth Maul engaged a PCBU, resulting in its total destruction, along with its droid pilot. Tragically, the two officers under the PCBU's protection also perished in the encounter.
During the Imperial era, 501-Z police droids took on the role of PCBU pilots.