A vehicle door security system comprising at least one deadbolt and respective operational elements, wherein the deadbolt secures at least one of a pivoting door and a roll up cargo door. The deadbolt toggles between an engaging configuration and a released configuration. The deadbolt can include an inertial release mechanism that disengages the deadbolt from the engaging configuration when the vehicle is subjected to a sudden impact. Alternatively, the deadbolt can be opened using a manual release mechanism located externally from the vehicle.