Warning Track
A strip of dirt that tells an outfielder with his eyes up that the wall is coming.
What it actually is. The warning track is the band of dirt or crushed brick running in front of the outfield wall, usually about fifteen feet wide. Its purpose is entirely tactile: an outfielder running back with his head turned to the ball feels the surface change under his feet and knows he has roughly two more steps.
What somebody who knows the game gets out of it. It is a safety feature that became a unit of measurement. Warning track power, a swing that produces long fly balls that die at the fence, is one of the most useful informal scouting phrases there is, because it identifies a hitter whose exit velocity is fine and whose launch angle is slightly wrong. The modern version of that observation is expected slugging, and the hitters it flags are almost exactly the ones scouts have been describing that way for fifty years.
The numbers worth knowing. Typically 15 feet wide, sometimes wider in older parks. A fly ball dying on the track is usually one hit around 95 to 100 mph at a launch angle a few degrees too high or too low.
What people get wrong about it. The track is in play. A catch made on it is an ordinary catch, and a fielder may reach into the stands beyond it as long as he does not use a fan for support. The track is not a boundary of any kind, it is simply a different surface.
At Little League and travel ball. Most youth fields do not have one, which is why running into fences is a genuine youth injury risk and why outfielders should be taught the drift back and the peek at the fence rather than relying on a surface change they will not feel.
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