Trucking Industry in The United States - Rules and Regulations - Hours of Service

Hours of Service

The FMCSA defines a CMV as a single or combination (truck and trailer) vehicle with a gross weight of 10,001 pounds (4,536 kg) or more, or a vehicle used to transport hazardous materials in quantities requiring the vehicle to be marked or placarded under the hazardous materials regulations. The length of time a driver may spend operating a CMV is limited by a set of rules known as the hours of service (HOS). These laws are designed to protect the general motoring public by reducing accidents caused by driver fatigue.

The first version of the HOS were enacted in 1938, and three revisions have been made since. The more recent revisions have relied on research into the human circadian rhythm (the tendency for humans to follow a natural 24-hour cycle with 8 hours of uninterrupted sleep). A driver is limited to 11 hours of actual driving within a 14-hour period, after which he/she must rest for 10 hours. The rules do not explicitly require that a driver must sleep, only that a driver must take a period of "rest" within the sleeper berth or off duty (i.e., at home).

Keeping track of a driver's HOS requires the use of a log book. A truck driver's log book is a legally defined form containing a grid outlining the 24-hour day into 15-minute increments. The driver must specify where and when he/she stopped between driving shifts, what duties were performed (if any), along with the driver's name, truck number, company info, and other information. The driver must also present his or her log book to authorities upon request, for inspection. In lieu of a log book, a motor carrier may substitute an electronic on-board recorder to record the driver's hours.