To provide a system for controlling an operable passive safety device.

This system is provided with operable headrest devices 44, 48 which assist protection of occupant on vehicle front seats 42, 43. A crush sensor 22 senses a condition of a vehicle 20 and supplies a crash sensor signal which has electric characteristics indicating the sensed vehicle condition. A control device 24 is connected to the headrest devices 44, 48 and the crash sensor 22, and determines an impact velocity value and an impact displacement value based on the crash sensor signal. The control device 24 has a threshold value relating in function to the impact displacement value, and responds to the determined impact velocity value relating to the threshold value, thereby controlling operation of the operable headrest devices 44, 48.