A magnetic detector of the passing of at least one vehicle wheel, a sensor of which is intended for being positioned on or in a roadway, and includes a conductive winding of at least one spiral and a ferrite structure inscribed in an elongated surface area, the conductive element being wound around a portion of the ferrite structure, parallel to its greater dimension. A stay member includes an outer portion situated beyond a seat in the outward direction of the vehicle body. The fish is carried along the transport track on a transport saddle. Because the seal does not buckle when installed, it does not require any additional installation steps as found in other similar inventions known in the art.