Identifying and Correcting Pulse Breakup Errors from Freeway Loop Detectors
نویسنده
چکیده
Loop detectors are the most common sensors used to collect freeway management data. There has been considerable research to screen the quality of loop detector data, but some significant detector errors have not received much attention due to the difficulty of identifying their occurrence. This paper examines one such error, pulse breakup: what should be a single pulse from a vehicle breaks up into two or more pulses because the detector momentarily drops out. We develop an algorithm to identify the presence of individual pulse breakup events. The algorithm is based on the nature of pulse breakup revealed from individual vehicle actuations with concurrent video ground truth. The algorithm begins with the comparison of the on-times from the two successive pulses bounding a given short off-time. To differentiate between pulse breakup and tailgating, the algorithm includes several comparisons of the adjacent on-times with respect to the ambient traffic conditions. A total of six steps are included in the algorithm. If two successive pulses satisfy all of the steps, these pulses are a suspected pulse breakup. Otherwise, these pulses are considered to arise from non-pulse breakup. The process is repeated over all pulses at each detector. The results can be used both to correct for the suspected pulse breakup events and the rate of suspected pulse breakup events provides an indication of the detector's health. The algorithm was tested over 68,281 actuations with concurrent video ground truth, in both free flow and congested conditions, from 15 detector stations (22 directional stations). As presented herein, the algorithm demonstrated good performance.
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تاریخ انتشار 2011