This striped flag is displayed by corner workers to signify debris on the track, which can be oil, sand, water, or some other substance.
(This striped flag; is displayed; by corner workers; to signify debris on the track) (the track; can be; oil, sand, water, or some other substance)
This striped flag the track
is displayed can be
by corner workers to signify debris on the track
oil, sand, water, or some other substance