Not that long ago automobiles had meters, gauges, for the driver to use.
Monitoring road speed, engine speed, water temperature, oil pressure, charging system, fuel amount......
Not enough knew what the information was telling them.
Not enough bothered looking at all.
So they replaced the meters with lights that light when limits are reached. ( Less expensive to build.)
Commonly known as Idiot Lights.
It is still important to look where you are driving.
Are you sure you had the green light ?
Don't Text and drive.
http://www.youtube.com/watch?v=LGdnGn8LO8E&feature=related