Patent ID: 7181414

Claim:
An ETC (electronic toll collection) system, consisting of: an antenna having a predetermined directivity for providing a limited radio-communication service zone that extends from the antenna and covers at least a portion of the area of a lane under the antenna, and which length along the lane is set to a distance which approximates a single vehicle; a single vehicle sensor within said system and positioned within said service zone at a location closer to oncoming vehicles than said antenna by a predetermined interval for detecting a vehicle which reaches a predetermined position defined in the limited radio-communication service zone, the predetermined position being defined by the location of the vehicle sensor such that only one vehicle is within said service zone and sensed by said vehicle sensor at any one time; first means for continuously transmitting a radio signal via the antenna independently of whether or not the vehicle sensor detects the vehicle; second means for deciding whether or not a radio response from a vehicle to the radio signal is received via the antenna; third means for, in cases where the second means decides that a radio response to the radio signal is received, judging that there is an ETC vehicle coming into the limited radio-communication service zone in response to the detection of a vehicle by said sensor within said service zone; and fourth means for, in cases where the vehicle sensor detects a vehicle while the second means decides that a radio response to the radio signal is not received, judging that there is a non-ETC vehicle coming into the limited radio-communication service zone.