The "Hours of Service" (HOS) regulations are rules set by the Federal Motor Carrier Safety Administration (FMCSA) to ensure that commercial drivers do not drive for too long without taking breaks. These regulations help prevent fatigue-related accidents by limiting the number of hours a driver can operate a vehicle in a given period. Drivers are required to take rest breaks and cannot exceed a certain number of driving hours per day or week. For example, a driver must take a 30-minute break after 8 hours of driving and cannot drive more than 11 hours in a single day.