Common use of LENGTH-BASED CLASSIFICATION Clause in Contracts

LENGTH-BASED CLASSIFICATION. As mentioned in Section 3.1, the frequency distribution of vehicle lengths clearly indicated a bimodal distribution with two distinct peaks, one higher peak centered at about 18 ft (5 m), representing the concentration of SV lengths, and the other centered at about 74 ft (23 m) representing LV lengths. Note that the distributions were split at 40 ft (12.2 m), which corresponds to the boundary between bins 2 and 3 of the WSDOT vehicle classification system outlined in Table 1-1. Trucks normally constitute less than 20 percent of traffic for major roadways in Washington State (WSDOT, 2002), which indicates that most of the detected vehicles on freeways are SVs. If a sufficient number of vehicle lengths are collected, the bimodal distribution can be applied to separate vehicles into SV and LV groups on the basis of relative length comparisons between vehicles. Relative comparisons to determine vehicle classification have been proven effective by ▇▇▇▇ and ▇▇▇▇▇ (2003) in developing more accurate speed estimation for single-loop detectors. The method can be extended further by using the apparent pixel-based length of vehicles rather than the physical length. This was feasible in the current study because the only desire was to classify vehicles by length, and it was not necessary to know the actual length of each vehicle, as long as it was properly classified. As soon as a vehicle exits the registration line, the length algorithm merely moves along the longitudinal line, counting the number of pixels as the pixel-based length of the vehicle. This ensures that the lengths of all the vehicles in a lane are measured at almost the same starting point, so that the measured vehicle lengths are comparable. Note that these are relative lengths, and a particular length measurement does not represent the actual length of the vehicle. In this manner, vehicles can be separated by length and classified without requiring camera calibration. This increases the flexibility and attractiveness of this mobile traffic detection system. ( e − s ) + ( e − s )