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What is Hours of Service (HOS)?

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Hours of service (HOS) is a term referring to the number of hours that a commercial motor vehicle driver may work per day, or week, or other period as mandated by the Federal Motor Carrier Safety Administration (FMCSA).

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Any driver who is subject to HOS regulations is required to limit the amount of time spent driving or on duty, to avoid exceeding a maximum amount set by HOS rules.

Another requirement is to maintain an accurate record of hours worked, available for inspection by law enforcement or officials of the FMCSA. This documentation is also known as records of duty status, or RODS.

The guidelines for hours of service and recordkeeping are set by the FMCSA; monitoring of driver and vehicle fleet HOS is carried out by this agency and by inspectors at highway checkpoints. Drivers or operators in violation of the rules are subject to penalties.

The full hours of service rules — number of hours permitted between breaks, required downtime, number of consecutive working days and more — may be found at the FMCSA site online.

Why HOS Rules Are Law

The federal government recognized long ago that public well-being depends on keeping the roads safe to travel. When a network of highways began to take shape in the United States and motor vehicles started carrying cargo and passengers over long distances, this created a problem: driver fatigue. Hours spent behind the wheel without a break led to accidents, and destruction of life and property.

Medical professionals and work safety analysts found that setting limits to driving time and mandating rest periods provided an effective means of reducing accidents.

Decades of research confirm these findings. For example, a study completed in 2013 found that based on the available data, a single modification to one of the rule provisions — what is known as the “restart break,” or period between completed work and rest cycles — would prevent approximately 1,400 crashes and 560 injuries, and save 19 lives each year.

Because they’ve been so successful in reducing accidents, HOS controls and the requirement to show compliance with them have existed for a long time. By federal law, commercial truck drivers have been maintaining written records of duty status since 1937.

Drivers who are Covered by HOS Regulation

The hours of service rules apply to persons who drive commercial motor vehicles, and the fleets that operate them. A commercial vehicle is one used for business purposes in interstate commerce, in any of these categories:

It weighs 10,001 pounds or more, or has a gross vehicle weight rating or gross combination weight rating of 10,001 pounds or more

It is designed or used to transport 16 or more passengers (including the driver) for any purpose, or 9 or more paying passengers

It is used for transporting hazardous materials in a quantity requiring placards.

HOS Verification and Enforcement

The Federal Motor Carrier Safety Administration conducts a nationwide program named the Safety Management System that is based on Compliance, Safety and Accountability (CSA), and monitors every commercial motor vehicle operator’s compliance with highway safety regulations.

The agency uses a broad range of criteria in assessing a carrier’s or driver’s safety, and these include adherence to hours of service rules. Any HOS violations recorded affect the operator’s overall CSA score.

The FMCSA uses these CSA scores to assess the performance of the commercial carrier against its peers in the industry. Some parts of the score are made public and may be viewed by potential clients as well as other trucking companies.

The Federal Motor Carrier Safety Administration considers HOS violations a serious danger to highway safety, and can exercise various sanctions against the carrier and/or the individual driver. Corrective measures may include a written warning, an investigation, financial penalties or loss of commercial certification.

HOS and Technology

Hours of service rules and compulsory documentation have been around a long time, but record keeping has become easier and more accurate following the introduction of electronic logging devices (ELDs). These replace paper logbooks or an earlier generation of electronic recorders and beginning in 2017 are required equipment for commercial trucking operations.

Drivers who currently use paper logs must convert to an ELD or other type of automatic on-board recording device, which meets the specifications of the rule, by Dec. 18, 2017. By Dec. 16, 2019, equipment used for recording HOS must be registered and certified ELD products as shown in the finalized FMCSA list on that date.

An ELD incorporates a small tablet device that the driver can carry in the vehicle, and the system may include other hardware and software that transmits information and provides two-way communication between a driver and the company’s base of operations. This technology confers multiple advantages over the old system of writing in paper logbooks. The devices represent a dramatic gain in convenience and accuracy, and decrease the administrative workload for drivers, fleet managers and government authorities.

As a response to dissent — and legal challenges — from some who disputed the need for electronic logging of HOS, organizations including the American Trucking Associations, the Trucking Alliance for Safety and Security and the Advocates for Highway Safety have all expressed support for the devices. In an official statement the ATA noted in 2016 that “While some may be reluctant to adopt ELD technology, that reluctance should not thwart the collective and broadly shared interest in a modern, safe and efficient transportation system.”

For more information on hours of service regulations and safety requirements, visit

To learn about our electronic logging devices, visit