| 摘要 |
Apparatus for detecting traffic information employs as a vehicle detector a composite inductance loop laid on a road of which traffic information is to be detected. The composite loop consists of a series combination of a large loop portion and a small loop portion. When a vehicle enters the small loop portion, the composite loop suffers a first pulse-like change in the inductance value thereof. As the vehicle moves from the small into the large loop portion the inductance value of the composite loop is reduced to a level lower than the level of the first pulse-like change and kept substantially at that level so long as the vehicle remains inside the large loop portion. When the vehicle is passing the opposite end of the large loop portion, the inductance value thereof again suffers a pulse-like change which is smaller than the first pulse-like change. From such changes in the inductance of the composite loop it will be possible to know traffic informations such as traffic volume, traffic density, vehicle speed, etc. The system may be provided with means for compensating for changes in the inductance of the composite loop caused by changes in environmental conditions.
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