A warning track is an area on a baseball field that is adjacent to the outfield fence. It is designed to warn players of their proximity to the fence and to help prevent injury. There are several synonyms for a warning track, such as caution strip, danger zone, alert line, hazard area, and safety margin. These terms all connote a sense of danger or warning, and serve to let players know where they are in relation to the boundaries of the playing field. A warning track is an essential safety feature on every ball field, and should always be respected and observed by players.