A seatbelt system may include a seatbelt configured to constrain a waist and a torso of an occupant. The seatbelt may also include a coupling configured to selectively couple a portion of a vehicle and the seatbelt to one another. The system may also include a reel configured to receive at least a portion of the seatbelt, and a tension sensor associated with the coupling and/or the seatbelt and configured to generate a signal indicative of tension in the seatbelt. The system may also include a deployment sensor associated with the seatbelt and configured to generate a signal indicative of a length of the seatbelt deployed from the reel. The system may also include an occupant detector configured to determine, based at least in part on the signals indicative of tension and the length, whether an occupant is properly wearing the seatbelt, such that the seatbelt constrains the occupant.