Abstract: An electrical system for providing an audible or visible warning and interior and exterior visible displays indicating whether the occupants of a motor vehicle have fastened their seat belts, in compliance with legal requirements and/or the will of the driver. The system involves a plurality of circuits each of which is associated with a driver's seat sensor switch, with a seat belt latch and with an interior display panel, and at least some of which are also associated with exterior display lights. Each said circuit has a seat belt latch for closing or opening said circuit, when the driver's seat sensor switch is closed, to change the condition of a light at a corresponding position on the interior display panel and, for at least the front seat belts, to change the condition of a corresponding exterior display light.