Apparatus for detecting a usage condition of a vehicle seat lap/shoulder belt

The usage condition of a vehicle seat lap/shoulder belt (18) is determined by detecting the proximity of the belt to at least one of the seat bight (34) and back cushion (16). A passive component (30, 36) is embedded or otherwise attached to at least one of the lap and shoulder portions (18a, 18b) of the belt (18), and at least one active component (32, 38) is disposed behind the trim fabric of the seat (10) to detect the proximity of the passive component (30, 36) to the seat. The proximity measurements are used in conjunction with other sensor data such as belt tension and/or state to reliably detect the presence of a rear facing infant seat and to discriminate between proper and improper lap/shoulder belt usage.