For 1990-2009 cars

When the key is turned to "RUN" or "START", a chime will come on for eight seconds to remind people to fasten their safety belts, unless the driver's safety belt is already buckled.

If the belt is not buckled, after the initial 8 seconds, the light will remain on steady for an additional 13 seconds. At this point, the light will begin to flash for an additional 55 seconds, and then go out. The light will go out immediately if the driver safety belt is buckled during this time.