30 CFR 57.14207 - Parking procedures for unattended equipment.
Mobile equipment shall not be left unattended unless the controls are placed in the park position and the parking brake, if provided, is set. When parked on a grade, the wheels or tracks of mobile equipment shall be either chocked or turned into a bank or rib.
Title 30 published on 2014-07-01
no entries appear in the Federal Register after this date.