Idiot Light

"Idiot light" is a term used to describe the dashboard indicator lights based on the idea that the light comes on only when a preventable problem has occurred, such as low oil. The idea is that generally people are not capable of reading the gauges properly(or at all) in order to avoid problems, and so the lights come on as a "Hey, moron! I needed oil like a month ago" indication. Take the example of a temperature gauge. The gauge measures the temperature of the engine and has a danger zone, marked with red. When the gauge reaches that point, the engine temperature warning light will come on. It is designed to draw the driver's attention to an immediate problem. A person who would just wait until the "engine temperature warning light" comes on to check the engine temperature could be called an "idiot".