The Merriam-Webster online dictionary defines tail lights, also called tail lamps, as warning lights, usually red, that are mounted at the back of a vehicle. The term predates the invention of the automobile, although it referred to essentially the same concept. The idea behind these lights is to provide more visibility for vehicles on the road, especially giving drivers following others an increased chance of seeing what is ahead. In fog, snow, or heavy rain, these red lights might be the only things that drivers can see of the vehicles ahead of them.