To take measures to avoid traffic accidents almost automatically without the need for substantial design changes or modification of traditional vehicles or the like.

The start operation of the vehicle is detected, and when the start operation of the vehicle is detected, a radio signal which promotes responses from an IC tag is sent. Then identifying information from the IC tag responding to the radio signal is received. When the identifying information received is in agreement with the predetermined identifying information, the start operation of the vehicle is made invalid. Alternatively, a state of a temporary stop of the vehicle is detected, and when the state of the temporary stop of the vehicle is detected, a radio signal which promotes responses from the IC tag is sent. Then identifying information from the IC tag responding to the radio signal is received. When the identifying information received is in agreement with the predetermined identifying information, the state of the temporary stop of the vehicle is continued.