| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a traffic congestion detection means that can detect a local event leading to shorter delay from the occurrence of the event to detection. <P>SOLUTION: An ETC on-vehicle equipment 10A measures received electric field intensity from received power when question signals transmitted at constant time intervals from a road side antenna unit 30 when proceeding into an event detection section and transmits ETC-ID and the received intensity (value) of the electric field which is measured as a responding signal to a road side processor 50 via the road side antenna unit 30. The road side processor 50 specifies the position of a vehicle by referring to the electric field intensity distribution data in the road side antenna unit 30 which is installed in the event detection section registered beforehand from the received ETC-ID, ID acquired time and the intensity value of received electric field. Then, the average speed of the vehicle in the event detection section is calculated from a plurality of electric field intensity information in the same ETC-ID and when the average speed is slower than a threshold value, judgement of a traffic congestion is made. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
