Abstract text

A wearable air bag device formed by defining air inflating chambers in a jacket of a rider of a vehicle. An ECU, a battery, a rider separation detecting part, a main switch and a warning device are incorporated into the jacket. A wire is connected to a vehicle via a connecting terminal. When a rider who wears the jacket is separated from the vehicle, the wire which is connected to the vehicle is extended and a reel is rotated. Upon detecting a rotational angular speed of the reel, the ECU determines that the rider is separated when the rotational angular speed is large. Upon detection of the separation of the rider, ECU develops an air bag by operating an inflator.