Section Travel-Time Measurement Using Inductance Signatures of Loop Detectors

Principal Investigator:

Taek Kwon, Professor, UMD-Electrical Engineering

Project Summary:

Travel-time data provides vital information for traffic monitoring, management, and planning. The objective of this research was to develop a new computational approach that could accurately measure travel time from two sets of spatially separated pavement-embedded loop detectors using re-identification of vehicle inductance signatures generated by the loops. Although measuring travel time using loop inductance signatures is not new, all past approaches essentially relied on pattern matching of raw inductance waveforms without restoring the detailed features lost due to the large detection zone of inductive loops. The main effort in this research was to develop a new computational algorithm that restores the lost details from the raw inductance waveforms by modeling the output of loop detectors as a convolution of the original vehicle signature and the loop system function. This restoration problem was formulated as a blind deconvolution problem because neither the impulse response of the loop detectors nor the original vehicle signature were known. To solve this blind problem, two basic blind deconvolution approaches were used: Godard deconvolution and constrained least squares. Experimental results showed that both methods performed well and significantly exposed the original signature information with unique vehicle characteristics.

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