Lexus LM 350h

From UK-spec and AU-spec LM owners' manual:
"Rear passengers’ seat belt reminder lights *1 (warning buzzer) *2
*1: This light illuminates on the multi-information display.
Regardless of whether or not a rear passenger is present, if the power switch is turned to ON with the rear seat belts unfastened, this light will also illuminate for a certain period of time.
*2: Rear passengers’ seat belt warning buzzer:
The rear passengers’ seat belt warning buzzer sounds to alert the rear passenger that his or her seat belt is not fastened. If the seat belt is unfastened, the buzzer sounds intermittently for a certain period of time after the seat belt is fastened and unfastened and the vehicle reaches a certain speed."