Which principle is utilized by a loop for vehicle detection?

The principle utilized by a loop for vehicle detection is inductance. In traffic signal systems, inductive loops are embedded in the pavement to sense the presence of vehicles. When a vehicle approaches the loop, it disrupts the electromagnetic field generated by the loop. This disruption is due to the change in inductance caused by the metal mass of the vehicle affecting the loop's magnetic field.

Inductive loops operate based on Faraday's law of electromagnetic induction, which states that a change in magnetic field within a coil of wire induces a voltage across the wire. As the vehicle passes over or stops within the loop, the inductance value changes, and this change can be detected to signal the traffic control system about the presence of a vehicle. This makes inductance the fundamental principle for vehicle detection in these systems, enabling them to operate effectively in monitoring traffic flow and managing signal timings.