US Patent 9514643 Above ground loop system proximity detection

A loop detection apparatus and corresponding methods are provided that includes an inductive loop and a processing device. The processing device includes circuitry to connect to the inductive loop and control and sense from the inductive loop a change in a characteristic thereof. The inductive loop is disposed at least partially above a surface on which a vehicle travels. The processing device detects a change in a characteristic of the inductive loop beyond a first threshold value, and in response, transmits a first signal configured to effect a first action. The processing device further detects a change in the characteristic of the inductive loop beyond a second threshold value, and in response, transmits a second signal configured to effect a second action different than the first action.