A human body communications transmitter is provided to a vehicle body, for transmitting an activation signal by using the human body of a rider as a transmission path on the basis of an instruction from an on-vehicle ECU. A human body communications receiver is provided to an airbag jacket for receiving the activation signal which is transmitted by using the human body of the rider as the transmission path. The in-jacket ECU inflates and thus deploys the airbag jacket upon receipt of the activation signal for the airbag jacket through either human body communications or radio communications. The human body communications transmitter is connected to a right handlebar portion electrode, a left handlebar portion electrode, a seat portion electrode, a right footrest portion electrode and a left footrest portion electrode. The human body communications receiver is connected to an in-jacket electrode adjacent to the human body.