Vehicle detection method

A vehicle detection method for identifying a number of axles of each passing-by vehicle and determining a total number of passing-by vehicles, comprising:

• acquiring a first output of a first sensor that detects vibrations of a structure and a second output of a second sensor that detects vibrations at a location different from a location of the first sensor on the structure, wherein the vibrations are generated by one or more vehicles that have passed over the structure, and each of the one or more vehicles can have any number of axles;
• detecting a plurality of peaks of the first output and detection times of the plurality of peaks of the first output, each peak of the first output corresponding to an axle of the one or more vehicles that has passed over the first sensor;
• detecting a plurality of peaks of the second output and detection times of the plurality of peaks of the second output, each peak of the second output corresponding to an axle of the one or more vehicles that has passed over the second sensor;
• and
• determining a number of vehicles that have passed over the structure based on the detections of the first sensor and the second sensor and, the determination of the number of vehicles that have passed over the structure comprising:
• extracting a first number n of first peaks for one vehicle moving on the structure from the plurality of peaks of the first output;
• extracting a second number m of second peaks for the one vehicle moving on the structure from the plurality of peaks of the second output;
• and
• when n is larger than m,
• creating nCm first combinations of the peaks from the plurality of first peaks, wherein nCm=n!/m!(n−m)lΔ
• calculating first differences between detection times of the plurality of first peaks and detection times of the plurality of second peaks in order of the detection times for each combination of the first combinations,
• calculating first variation indexes of the first differences for each combination of the first combinations,
• selecting a combination of the peaks having the smallest first variation index among the first combinations, and
• determining that the selected combination of the peaks are generated by a single vehicle having m axles;
• and
• when n is smaller than m,
• creating mCn second combinations of the peaks from the plurality of second peaks, wherein mCn=m!/n!(m−n)lΔ
• calculating second differences between detection times of the plurality of first peaks and detection times of the plurality of second peaks in order of the detection times for each combination of the second combinations,
• calculating second variation indexes of the second differences for each combination of the second combinations,
• selecting a combination of the peaks having the smallest second variation index among the second combinations, and
• determining that the selected combination of the peaks are generated by a single vehicle having n axles.