The hours of service (HOS) are regulations issue by the Federal Motor Carrier Safety Administration (FMCSA) governing the working hours of anyone operating a commercial motor vehicle (CMV) in the United States for the purpose of interstate commerce. This includes truck drivers and bus drivers who operate CMVs for motor carriers (their employers). These rules limit the number of daily and weekly hours spent driving and working, and regulate the minimum amount of time drivers must spend resting between driving shifts. For intrastate commerce, the respective state's regulations apply.