University of California Transportation Center

Interstate motor carriers are subject to limitations on the hours that their drivers may be on-duty and driving. The regulations include a requirement that a driver be off-duty for a minimum of 8 hours after driving for 10 hours or being on-duty for 15 hours. There are also cumulative restrictions for on-duty time over several days: 70 hours on duty in 8 days for carriers operating 7 days a week and 60 hours in 7 days or those operating 5 days a week. These limitations, referred to as the hours of service regulations, were initiated in the 1930's. Since then the U.S. highway system has changed dramatically as has the nature of the trucking business and the technology of the vehicles. Despite these changes, there have been rather limited attempts to assess the safety implications of the hours of service for contemporary conditions.