For jobs requiring local/regional travel from home to clients, what are the actual hours worked?

This job requires at least 80% client-based or off-site work. When not meeting with a client or visiting an off-site location, work is conducted at the main office. On days when employee works with clients, he/she travels from home and does not go to main office.

If the work-day is 8.0 hours, what is considered hours worked when not reporting to the main office? Is travel from home to client considered hours worked? Or, is normal commute time (travel from home to main office) deducted from travel time from home to client?