36 CFR Part 1191 ABA Accessibility Guidelines, Outdoor Developed Areas - Preamble

1016.6 Openings

This section requires openings in the surface of outdoor recreation access routes, passing spaces, and resting intervals such as spaces between the boards in a boardwalk and drainage grates to not allow passage of a sphere more than 1/2 inch in diameter. Where possible, drainage grates should be located outside the minimum clear width of the recreation access route. Elongated openings should be placed so that the long dimension is perpendicular, or as close to perpendicular as possible, to the dominant direction of travel.