Car traffic monitoring system using MI sensor built-in disk set on the road

A new car sensing system using an amorphous wire CMOS magneto-impedance (MI) sensor built into a disk set on the road is presented. When a car passes above the disk, the MI sensor detects stray fields from the car body. The speed and length of a car can be estimated processing the signals from two MI sensors. A prototype disk with two MI sensors, a microcomputer, and a semiconductor IC memory built-in has been developed. The disk system can record the length, the velocity and the time when a car passed for two thousand cars. The proposed sensing system is useful for automatic traffic measurements.