Hours of service (HOS) regulations are issued by the Federal Motor Carrier Safety Administration (FMCSA) and govern the working hours of anyone operating a commercial motor vehicle (CMV) in the United States. These regulations apply to truck drivers, commercial and intercity bus drivers, and school bus drivers who operate CMVs. 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.
The FMCSA is a division of the United States Department of Transportation (DOT), which is generally responsible for enforcement of FMCSA regulations. The driver of a CMV is required to keep a record of working hours using a log book, outlining the total number of hours spent driving and resting, as well as the time at which the change of duty status occurred. In lieu of a log book, a motor carrier may keep track of a driver's hours using electronic logging devices (ELDs). These devices are a form of telematics used in fleet management to automatically record driving time and other vehicle data.
The HOS's main purpose is to prevent accidents caused by driver fatigue. This is accomplished by limiting the number of driving hours per day, and the number of driving and working hours per week. Fatigue is also prevented by keeping drivers on a 21- to 24-hour schedule, maintaining a natural sleep/wake cycle (or circadian rhythm). Drivers are required to take a daily minimum period of rest, and are allowed longer "weekend" rest periods to combat cumulative fatigue effects that accrue on a weekly basis.
Enforcement of the HOS is generally handled by DOT officers of each state, and are sometimes checked when CMVs pass through weigh stations. Drivers found to be in violation of the HOS can be forced to stop driving for a certain period of time, which may negatively affect the motor carrier's safety rating. Requests to change the HOS are a source of contentious debate, and many surveys indicate some drivers get away with routinely violating the HOS. These facts have started another debate on whether motor carriers should be required to use ELDs in their vehicles, instead of relying on paper-based log books.
Purpose
Drivers subject to the HOS include any driver of a vehicle which has a gross vehicle weight of or more; which is designed or used to transport more than 8 passengers (including the driver) for compensation; which is designed or used to transport more than 15 passengers (including the driver) and is not used to transport passengers for compensation; or which is used to transport hazardous materials in quantities requiring the vehicle to be marked or placarded under the hazardous materials regulations.
The purpose of the HOS is to reduce accidents caused by driver fatigue. As the graph to the right illustrates, the number of hours spent driving has a strong correlation to the number of fatigue-related accidents. According to numerous studies, the risk of fatigue is also greatest between midnight and 6:00 a.m., and increases with the total length of the driver's trip. The blanket assignment of midnight as the time of day when all drivers gain fresh hours may therefore not be the safest choice possible.
The FMCSA identifies three main factors in driver fatigue: Circadian rhythm effects, sleep deprivation and cumulative fatigue effects, and industrial or "time-on-task" fatigue.
Circadian rhythm effects describe the tendency for humans to experience a normal cycle in attentiveness and sleepiness through the 24-hour day. Those with a conventional sleep pattern (sleeping for seven or eight hours at night) experience periods of maximum fatigue in the early hours of the morning and a lesser period in the early afternoon. During the low points of this cycle, one experiences reduced attentiveness. During the high points, it is difficult to sleep soundly. The cycle is anchored in part by ambient lighting (darkness causes a person's body to release the hormone melatonin, which induces sleep), and a person's imposed pattern of regular sleeping and waking times. The influence of the day-night cycle is never fully displaced (standard artificial lighting is not strong enough to inhibit the release of melatonin), and the performance of night shift workers usually suffers. Circadian rhythms are persistent and can only be shifted by one to two hours forward or backward per day. Changing the starting time of a work shift by more than these amounts will reduce attentiveness, which is common after the first night shift following a "weekend" break during which conventional sleep times were followed.
Sleep deprivation and cumulative fatigue effects describe how individuals who fail to have an adequate period of sleep (7–8 hours in 24 hours) or who have been awake longer than the conventional 16–17 hours will suffer sleep deprivation. A sleep deficit accumulates with successive sleep-deprived days, and additional fatigue may be caused by breaking daily sleep into two shorter periods in place of a single unbroken period of sleep. A sleep deficit is not instantly reduced by one night's sleep; it may take two or three conventional sleep cycles for an individual to return to unimpaired performance.
Industrial or "time-on-task" fatigue describes fatigue accumulated during the working period and affects performance at different times during the shift. Performance declines the longer a person is engaged in a task, gradually during the first few hours and more steeply toward the end of a long period at work. Reduced performance has also been observed in the first hour of work as an individual adjusts to the working environment.
Definition of terms
Parts of a driver's work day are defined in four terms: On-duty time, off-duty time, driving time, and sleeper berth time.
FMCSA regulation §395.2 states:
On-duty time is all time from when a driver begins to work or is required to be in readiness to work until the driver is relieved from work and all responsibility for performing work.
On-duty time includes:
All time at a plant, terminal, facility, or other property of a motor carrier or shipper, or on any public property, waiting to be dispatched, unless the driver has been relieved from duty by the carrier All time inspecting, servicing, or conditioning any CMV at any time Crossing a border All driving time as defined in the term "driving time" All time, other than driving time, in or upon any CMV except time spent resting in a sleeper berth All time loading or unloading a CMV, supervising, or assisting in the loading or unloading, attending a CMV being loaded or unloaded, remaining in readiness to operate the CMV, or in giving or receiving receipts for shipments loaded or unloaded All time repairing, obtaining assistance, or remaining in attendance upon a disabled CMV All time spent providing a breath sample or urine specimen, including travel time to and from the collection site, to comply with random, reasonable suspicion, post-accident, or follow-up drug testing Performing any other work in the capacity, employ, or service of a motor carrier Performing any compensated work for a person who is not a motor carrier (This rule does not explicitly forbid a driver from obtaining a second or part-time job; it simply prevents a driver switching from a non-driving job to a driving job without the required 10 hours of rest)
Driving time is all time spent at the driving controls of a CMV.
Sleeper berth time is any amount of time spent inside the sleeper berth (e.g., resting or sleeping). FMCSA regulation §393.76 gives the minimum requirements for a space to be defined as a sleeper berth. The simple definition is an area separate from (usually immediately behind) the driving controls that includes a bed. 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., home). A statement made by the ICC in 1937 gives the reason: "We have no control over the manner in which a driver may spend his time off-duty, although some of his spare time activities may tire him as much as any work would do. We can only emphasize, by this comment, the responsibility which is the driver's own to assure himself of adequate rest and sleep, in the time available for this purpose, to ensure safety of his driving, and likewise the employer's responsibility to see that his drivers report for work in fit condition."
Off-duty time is any time not spent on-duty, driving, or in the sleeper berth.
History Summary of changes to the hours of service Year Enforced Driving Hours On-Duty Hours Off-Duty Hours Minimum Duty Cycle Maximum Hours On-Duty Before 30 Minute Rest Break 1938 12 15 9 24 None 1939 10 None 8 24 None 1962 10 15 8 18 None 20031 11 14 10 21 None 20131 11 14 10 34 8 1 Applies to property-carrying vehicles only.
In 1938, the now-abolished Interstate Commerce Commission (ICC) enforced the first HOS rules. Drivers were limited to 12 hours of work within a 15-hour period. Work was defined as loading, unloading, driving, handling freight, preparing reports, preparing vehicles for service, or performing any other duty pertaining to the transportation of passengers or property. The ICC intended the 3-hour difference between 15 hours on-duty and 12 hours of work to be used for meals and rest breaks. The weekly maximum was limited to 60 hours over 7 days (non-daily drivers), or 70 hours over 8 days (daily drivers). These rules allowed for 12 hours of work within a 15-hour period, 9 hours of rest, with 3 hours for breaks within a 24-hour day.
Within a short time, however, representatives of organized labor (including the American Federation of Labor, the Teamsters, and the International Association of Machinists) petitioned for a stay of the original regulations. A few motor carriers made a similar request. The ICC agreed, and oral arguments were heard again. Labor wanted HOS limits of 8 hours per day and 48 hours per week. The ICC commented "there was no statistical or other information which would enable [them] to say definitely how long a driver can safely work."
Within six months of the original ruling, the ICC ultimately decided to change the 12-hour work limit in 24 hours to a 10-hour driving limit in 24 hours, and the 15-hour on-duty limit was rescinded. Motor carriers were required to give drivers 8, rather than 9, consecutive hours off-duty each day. These rules allowed for 10 hours of driving and 8 hours of rest within a 24-hour day.
In 1962, for reasons it never clearly explained, the ICC eliminated the 24-hour cycle rule, and reinstated the 15-hour on-duty limit. With 10 hours of driving and 8 hours of sleep, drivers were allowed to maintain an 18-hour cycle, disrupting the driver's natural 24-hour circadian rhythm. This change allowed up to 16 hours of driving per day, allowing the driver to exhaust their weekly limits in as little as five days. Later, an added exception for trucks equipped with sleeper berths meant drivers were allowed to "split" their 8-hour off-duty time into two parts. With the new splitting provision, a driver could take two 4-hour periods of rest. Using one of these short rest periods would effectively "stop the on-duty clock", allowing the driver to split the 15-hour on-duty time limit into two parts as well. These rules allowed for 10 hours of work within a 15-hour time limit, and 8 hours of rest within an 18-hour day.