There is no denying the relationship between commercial motor vehicle operators, who work long daily and weekly hours, and chronic fatigue, a high risk of crashes and serious, chronic driver-health problems. In order to address the deleterious effect of fatigued driving on the health, safety and welfare of commercial motor vehicle operators and the general public alike, the Federal Motor Carrier Safety Administration (“FMCSA”) began revising and updating its hours-of-services rules approximately 14 years ago. Generally speaking, the hours-of-service rules govern the number of hours that a commercial motor vehicle operator can drive and work in a given day and week. Recently, the FMCSA’s new hours-of-service rules took effect and the United States Court of Appeals for the District of Columbia issued an important ruling concerning challenges to the new rules. In the second and third parts of this three-part series, I will address the history of the hours-of-service rules as well as the most recent updates and challenges thereto.