However, sometimes on-duty time must be extended, such as an emergency situation following a severe storm. Use of sleeper berths. Rest or sleep acquired in a sleeper berth is not equivalent to rest or sleep in a bed, because vehicle motion, highway noise and other conditions disrupt restorative sleep. Cumulative on-duty time. Limits should be placed on the total on-duty hours allowed within a specified number of days, with allowance made for recovery time.
Cumulative fatigue occurs, and an extended off-duty time period is needed to recover.
Adequate recovery time. Sleep loss, extended hours of service, and unnatural schedules cannot be compensated for by a single night s rest. Recovery time periods must consider the necessity for overcoming cumulative fatigue resulting from such schedules and must include sufficient nighttime sleep. Recovery time should include at least two uninterrupted time periods between midnight and 6 a.m., and such recovery time should be made available at least once in every seven days. Foreknowledge of work schedule.