Innovative application of directional boring procedures for replacing failed inductive loop detectors

Abstract

Actuated traffic signal controllers typically depend on inductive loop detectors to determine demand for a particular signal phase. The basic philosophy of these controllers is to only provide a green indication to a particular lane group when there is a vehicle waiting. If an inductive loop detector fails, it must be put in recall mode so that the lane group with the corresponding failed detector is serviced every cycle. When actuated controllers operate in this mode, the performance of the signalized intersection degenerates. Since the vast majority of actuated intersections operate with inductive loop detectors it is useful to have maintenance procedures that can be used to replace loop detectors that have failed due to pavement distress. This paper describes a procedure that has been developed using directional boring equipment to install a micro loop below the surface of the pavement where it is not subject to pavement distress. The authors believe this procedure will provide a cost effective method of restoring actuated control on approaches or lanes groups where the pavement condition makes it unfeasible to install or re-install a traditional saw cut loop detector.