sløyfedetektor

A sløyfedetektor, also known as an inductive loop detector or simply a loop detector, is a common traffic control device. It is an electronic device used to detect vehicles. The fundamental principle of operation relies on a change in inductance within a wire loop embedded in the pavement.

A sløyfedetektor consists of a coil of wire, typically rectangular or square, buried in the road surface. This coil is connected to a detector unit. When current flows through the coil, it generates a magnetic field. As a vehicle, which is made of metal, passes over or into the loop, it disturbs this magnetic field. This disturbance causes a change in the inductance of the coil.

The detector unit continuously monitors the inductance of the loop. When a vehicle is present, the inductance changes, and this change is detected by the unit. The detector then signals the presence of the vehicle to a connected traffic signal controller, gate opener, or other traffic management system.

Sløyfedetektors are widely used at traffic intersections to control traffic lights, enabling them to adapt to traffic flow by extending green light times or triggering new green cycles when vehicles are detected. They are also employed in toll booths, parking garages, and for traffic counting applications. Their reliability and relatively low cost have made them a standard component in traffic engineering for many decades. Variations exist, including single-loop detectors and dual-loop detectors, which can provide additional information such as vehicle speed and presence duration.