|This article does not cite any references or sources. (October 2007)|
The warning track is the part of the baseball field that is closest to the wall or fence and is typically made of dirt, instead of grass or artificial turf like most of the field. It runs parallel to the ballpark's wall and looks like a running track. The change of terrain from grass to dirt serves as a "warning" for fielders trying to make a deep catch that they are running out of room, since it is often difficult for the fielder to keep his eye on a fly ball while keeping track of his position relative to the wall.
Despite the warning track's presence, it is common to see outfielders crash into the wall to make a catch, due either to a desire to field the play regardless of the outcome or because they fail to register the warning.
The term "warning track" comes from Old Yankee Stadium, where an actual running track was built for the use of track and field events. This also helped outfielders know when they were approaching the wall, and soon every ballpark was using one. However, there still are professional fields without a proper warning track, such as the Tokyo Dome, which instead has it represented by a white line, the same way as the infield dirt is "marked" on an artificial turf.
The average length of the warning track (depending on the ballpark) is 690 ft while the width is 15 ft.