The ornamental design for a high visibilitysheetmaterial, as shown and described.
FIG. 1 is a front view of a high visibility sheet material showing my new design.
FIG. 2 is a side elevation view thereof, an opposite side view being identical;
FIG. 3 is a perspective view thereof; and,
FIG. 4 is a rear view thereof.
The broken lines in the drawings depict boundaries of the claim and define symbolic breaks in the length and width and form no part thereof. Any portion of the article between the break lines forms no part of the claimed design.