ABA Accessibility Standard for GSA Facilities Pocket Guide
404.2.4.4 Floor or Ground Surface.
Floor or ground surface within required maneuvering clearances shall comply with 302. Changes in level are not permitted.
EXCEPTIONS: 1. Slopes not steeper than 1:48 shall be permitted.
2. Changes in level at thresholds complying with 404.2.5 shall be permitted.