Method and apparatus for monitoring traffic flow

  • US 5,296,852 A
  • Filed: 02/27/1991
  • Issued: 03/22/1994
  • Est. Priority Date: 02/27/1991
  • Status: Expired due to Fees
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First Claim
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1. A method for determining the speed of a vehicle traveling along a predetermined path, comprising the steps of:

  • generating a reference image of a section of said path;

    transducing said reference image into a reference array of pixels;

    generating successive images of said section of said path;

    transducing said successive images into successive arrays of pixels;

    separating each one of said arrays of pixels into first and second subarrays of pixels, each of said subarrays corresponding to first and second portions of said path, said first and second portions of said path being separated by a known distance;

    summing the intensity values of all the pixels in said first subarray of said reference array;

    summing the intensity values of all the pixels in said first subarray of each one of said successive arrays;

    successively comparing the pixel intensity sum for each said first subarray of each one of said successive arrays to the pixel intensity sum for said first subarray of said reference array;

    generating data indicative of the presence of said vehicle in said first portion of said path when the difference in pixel intensity sums between said first subarrays recited in said comparing step exceeds a predetermined value;

    recording a first reference time when said vehicle is first determined to be present in said first portion of said path;

    summing the intensity values of all the pixels in said second subarray of said reference array;

    summing the intensity values of all the pixels in said second subarray of each one of said successive arrays;

    successively comparing the pixel intensity sum for each said second subarray of each one of said successive arrays to the pixel intensity sum for said second subarray of said reference array;

    generating data indicative of the presence of said vehicle in said second portion of said path when the difference in pixel intensity between said second subarrays recited in said last-recited comparing step exceeds said predetermined value;

    recording a second reference time when said vehicle is first determined to be present in said second portion of said path; and

    calculating the speed of said vehicle from the difference in said first and second reference times and said known distance between said first and second portions of said path.

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