System and method for detecting the correct fastening of a seat belt

The present invention relates to a detection system and method for detecting the correct fastening of a seat belt. The system comprises: weighing means for obtaining the weight ( P ) of the seated person; sensor means for detecting the fastening of the belt; sensor means for measuring the length of an unwound band for obtaining the length ( L ) of an unwound seat belt band; control means for: ¢ detecting (300) the fastening of the belt; ¢ obtaining (302) the length ( L ) of an unwound band; ¢ obtaining (302) the weight ( P ) of the person on the seat; ¢ determining (308,314) whether the seat belt is correctly fastened depending on the detection (300) of the fastening of the belt and on the values of length ( L ) of the unwound band and of weight ( P ). It is used to permanently control the correct fastening of the seat belt of the occupants of the vehicle.