Patent ID: 6483443
Filing Date: 2002-11-19
Classification: G08G

Abstract:
Loop sensing apparatus for detecting vehicles travelling along a lane of a roadway, the apparatus comprising an outer loop configured to provide at least one primary surface region of the roadway lane over which magnetic field produced by current in the outer loop has the sane polarity, an inner loop sized to fit and located within said primary surface region, said inner loop being configured to provide a first partial surface region of the roadway lane which is within said primary surface region and over which magnetic field produced by a current in said inner loop has a first polarity and a second partial surface region of the roadway lane which is within said primary surface region and over which magnetic field produced by the same current in said inner loop has a second polarity opposite to said first polarity, and detection circuitry connected to permit each of said outer and inner loops to be energised individually and arranged to be responsive to respective detection signals generated in each of the loops by vehicles passing over the loops.