My dispatcher tells me that time waiting for a load is off duty time. I think the rules say it's on duty. Which is true?
Technically speaking, any time spent at any job-related activity, other than driving, is considered on-duty time. This might include loading, fueling, awaiting a dispatch, waiting for the vehicle while it's being repaired, or just about anything you do on behalf of the company.
Dispatch may be concerned that you're burning up too many hours by logging on duty when he tells you to call back every 15 minutes. Unless he has author-ized you to log off-duty during that time, you're supposed to be logging on-duty. You'll need a letter from the carrier releasing you from all responsibilities while you're off-duty, and the letter must make it clear that while you're off duty, you must be free to pursue an activity of your choosing. If you think about, how can you be free to pursue an activity of your choosing, if you're required to call back every 15 minutes?