Activation device for passenger protection apparatus

An activation device for a passenger protection apparatus which is made to activate said passenger protection apparatus in accordance with a behavior of a vehicle, comprising:

• an angular velocity sensor for detecting a roll angular velocity of said vehicle;
• relative angle calculating means for calculating a roll relative angle of said vehicle on the basis of the roll angular velocity detected by said angular velocity sensor;
• roll judging means for making a judgment indicating the occurrence of a roll of said vehicle when the roll angular velocity detected by said angular velocity sensor and the vehicle roll relative angle calculated by said relative angle calculating means satisfy a predetermined threshold condition;
• drive control means for activating said passenger protection apparatus when said roll judging means makes the vehicle roll judgment;
• state detecting means having at least one of a window opening/closure sensor for detecting an open/closed state of a window of said vehicle and a buckle switch for detecting a wearing state of a seat belt;
• and
• threshold setting means for setting said predetermined threshold condition on the basis of a result of the detection by said state detecting means.