A driver is on duty from the time he begins to work or is required to be in readiness for work until the time he is relieved from work and all responsibility for performing work, and includes time for meals.

The term driving time includes all time spent on a moving vehicle and any interval not in excess of 10 minutes in which a driver is on duty but not on a moving vehicle.

The term off duty means free and off the motor truck and/or motor bus and free from work of any kind in such places and under such circumstances that rest and relaxation from the strain of the duties of employment may be obtained. Time spent by a driver in a sleeper berth in such vehicle shall not be considered off duty, but shall be considered time on duty.