sentence: Warning lights help stop accidents.
sentences_before: Visibility less than  is often called zero. When it is this low, roads may be closed, or lights and signs are turned on to warn drivers. These are put in areas that often have very low visibility.
sentences_after: Automobile crashes with many cars happen often in places like this if the warning lights and signs are not put up.
concept_name: warning light
headings: Visibility
categories: Weather