Patent ID: 8791839

Claim:
A method of recognizing the presence of a passenger in front of a door of a transit vehicle comprising the steps of: at preset multiple positions of the door as it is opening or closing directing an ultrasound transmitter/receiver at a volume of space adjacent the door and generally directed at the floor in front of the door; emitting an ultrasound pulse via the transmitter/receiver into said volume of space while the space is not occupied by a passenger; recording the ultrasound echoes from objects in the volume of space for at least one response period; integrating intensity of said echoes during at least a fixed portion of the at least one response period and storing the integrated values as standard values; repeatedly at preset multiple positions of the door as it is opening or closing emitting an ultrasound pulse via the transmitter/receiver into said volume of space, recording the ultrasound echoes, and integrating the intensity of said echoes during said fixed period; and repeatedly comparing the integrated values to the stored standard value such that when the integrated value differs from the standard value for each preset position by a given amount, a passenger is deemed to have entered the volume of space adjacent the door.