State Demonstration Project: Loop Detectors

About the report:

The Virginia Department of Highways and Transportation frequently utilizes induction loops in its vehicle detector systems. Although not documented, there have been many instances of loop failure; therefore, the practices and materials used by the Department in installing loop detectors were investigated. Two field tests were initially undertaken-- the encasement of the loop wires by PVC conduit and vinyl tubing and the performance of different types of loop sealants. Also, laboratory tests were undertaken to further evaluate the performance of loop sealants, to determine the type and quantity of sand to add to epoxy sealants, and to derive the expansion factor of the resulting mixture. Finally, a third field test was undertaken to evaluate several of the laboratory findings. This report provides the status of the first two demonstrations and documents the findings and Conclusions of the laboratory tests and the third field test. Several recommendations concerning the expansion factor, the current sealant specifications, and the required width of saw cut are made.

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