A ferromagnetic loop having a footprint characterized by a continuous wire shaped in a serpentine manner to form multiple contiguous polygons within the footprint for detection of moving vehicles. The footprint can be one of a triangle, a square, a rectangle, a rhombus, a parallelogram, an ellipse, or a circle. Similarly, each of the multiple contiguous polygons can be one of a triangle, a square, a rectangle, a rhombus, a parallelogram. Different design configuration for the ferromagnetic loop and methods for making and using the same are disclosed.