Studies suggest that fatigue and/or sleep deprivation may be a contributing factor in at least 30 to 40 percent of all heavy truck crashes. In this article, human factors expert, Dr. Nancy Grugle, and commercial trucking expert, Brooks Rugemer, explore the effects of sleep deprivation and how the trucking industry works to improve safety on the roadways.
According to the National Highway Traffic Safety Administration (NHTSA), sleep deprivation is a factor in almost 100,000 motor vehicle accidents and 1,550 fatalities per year in the United States (www.nhtsa.gov). With respect to heavy truck crashes specifically, past studies suggest that fatigue and/or sleep deprivation may be a contributing factor in at least 30 to 40 percent of crashes (NTSB, 1995). These statistics are not surprising considering that a survey of long-haul truck drivers reported that 66% of drivers acknowledged experiencing some level of fatigue on at least half of their trips and 65% reported symptoms of drowsiness such as yawning, feeling drowsy or sleepy, and struggling to stay alert while driving. Critically, 13% of drivers reported actually falling asleep at the wheel (Dinges and Maislin, 2006).
The Effects of Sleep Deprivation
Sleep deprivation affects a driver’s ability to safely operate a motor vehicle by increasing reaction time, degrading attention and vigilance, increasing distractibility and confusion, decreasing motivation, and increasing the probability of driving performance errors (Gawron, 2012; Barfield, et al., 1995). The first behavioral signs of sleep deprivation often include changes in mood and motivation, failure to complete routines and slower responses (Giam, 1997).
Long-distance truck drivers on overnight or early morning routes are even more susceptible to the effects of sleep deprivation than during normal daylight hours because of disruptions to their natural sleep patterns by working nights or long and irregular hours. Additional factors that may contribute to fatigue while driving a commercial truck include darkness and monotonous driving environments (Hanowski, et al., 1998).
Time of day is the largest factor contributing to fatigue/reduced alertness in commercial trucking and is the best predictor of crashes (Wylie, et al., 1996). A large, on-the-road study of commercial drivers found that drowsiness episodes were 8 times more likely between midnight and 6am than during other times of the day. Other studies have found that drivers are 20 times more likely to fall asleep while driving at 6am than at 10am (Harrison and Horne, 1999).
The graphic below shows the times of day when a driver is most susceptible to the effects of sleepiness based on the body’s circadian rhythm (Rhodes and Gil, 2002). The circadian rhythm is the body’s internal clock that regulates a person’s sleep patterns and fatigue (Banks et al., 2012). As sleepiness increases, a driver’s alertness decreases. Most drowsy driving crashes occur between midnight and 8am and between 1pm and 3pm, consistent with decreased alertness as predicted by dips in their circadian rhythm.
In response to safety concerns about the high number of fatigue-related heavy truck crashes, the Federal Motor Carrier Safety Administration (FMCSA) adopted new federal hours-of-service regulations for commercial motor vehicle drivers which went into effect in July 2013.
Hours of Service Regulations
The Federal Motor Carrier Safety Administration (FMCSA) publishes a set of rules that limit the maximum amount of time truck drivers can work and drive before taking a required break. The Hours of Service (HOS) rules identify a truck drivers’ time as falling into one of four categories:
- Off Duty – Time when a truck driver is free from any work related responsibility.
- Sleeper Berth - Time spent physically in the sleeping compartment of a commercial truck for the purpose of obtaining sleep and rest,
- Driving – All time spent at the driving controls of a commercial motor vehicle in operation
- On Duty – Not Driving - All time from the time a driver begins to work or is required to be in readiness to work until the time the driver is relieved from work and all responsibility for performing work.
“Driving” and “On Duty – Not Driving” time is combined to determine the total hours a truck driver can work.
Truck drivers must record, or “log”, their time, activity, and location in a logbook:
In its simplest form*, the FMCSA mandates:
- Once reporting on duty, a truck driver can drive / work a maximum 14-hour shift before they are required to go off duty or into the sleeper berth for 10 hours.
- During that 14-hour shift, a truck driver can drive a maximum of 11 hours.
- A truck driver may not drive once they reach 60 hours of work / driving in a 7 day period, or 70 hours in an 8 day period.
(*some variations apply depending on the nature of the trucking operations)
Trucking Company Responsibilities
Trucking is a 24/7 business. It is not uncommon for a truck driver to be awake and working during every hour on the clock over a week’s time. Add to this the difficulties of attempting to get proper sleep during times when people are typically awake.
Motor Carriers have a duty to develop Safety Management Controls and Oversight of their truck drivers. These Management Controls must include:
“systems, policies programs, practices, and procedures used by a motor carrier to ensure … the safe movement of products and passengers through the transportation system, and to reduce the risk of highway accidents … resulting in fatalities, injuries, and property damage. (FMCSR 385.3 – excerpted)
Parts of these Safety Management Controls are a Motor Carriers’ Training Program. Motor Carriers have a duty to train their trucking driving fleet in how to properly use the Hours of Service rules. A proper Training Program should also include planning a safe and legal trip, proper time management, and other awareness measures to help their truck drivers stay safe and for the protection of the motoring public.
Motor Carriers and Commercial Truck Drivers share in the duty to work within the limitations of the federal regulations. They both share in the duty to set reasonable time tables and transit schedules.
Role of Fatigue in Commercial Truck Crashes
The role that sleep deprivation or fatigue may have played in a truck driving crash is a complex issue. Experts with specialized knowledge and expertise in the areas of sleep deprivation and human factors as well as hours-of-service regulations and trucking safety programs conduct investigations using a combination of accident analysis techniques, knowledge of human behavior and performance, and experience investigating trucking safety violations to determine the relevant factors in a crash.
Some of the challenges with drowsy driving cases include (Job et al., 2012):
- There is no “sleepalyzer” test to determine how sleep-deprived a driver is
- Drivers aren’t always aware that they were asleep or may not report that they were asleep
- Drivers are often alert after a crash due to adrenaline and may not appear tired
- Truck drivers that have not violated HOS regulations can still be driving while sleep-deprived
Some initial indicators that fatigue or sleep deprivation may have been a factor in a crash include the following:
- A single vehicle leaves the roadway
- The crash occurs on a high-speed road
- The driver does not attempt to avoid crashing
- Fall-asleep crashes are likely to be serious
- The driver is alone in the vehicle
Despite the new HOS rules that were intended to reduce drowsy driving in commercial motor vehicles, a recent survey of truckers conducted by the American Transportation Research Institute found that 66% of drivers indicated increased fatigue while driving as a direct result of the new rules (ATRI, 2013). While these results may be surprising, it emphasizes the complexity involved in reducing drowsy driving in the commercial trucking industry. As a result, fatigue and sleep deprivation in trucking operations is likely to continue to be a major safety problem in the commercial trucking industry for the foreseeable future.
- National Transportation Safety Board Safety Recommendation, February 1995.
- Dinges, D and Maislin, G. (2006). Truck Driver Fatigue Management. (Project Report FMCSA-RRR-06-008). Washington, D.C.: U.S. Department of Transportation, Federal Motor Carrier Safety Administration.
- Gawron, V. (2012) Ch. 17: Sleep Loss and Performance. In The Handbook of Operator Fatigue. Matthews et al., (Eds.) Pgs. 263-296.
- Harrison, Y., and Horne, J. (1999). One night of sleep loss impairs innovative thinking and flexible decision making. Organizational Behavior and Human Decision Processes, 78(2), 128-145.
- Wylie, C., Shultz, T., Miller, J., Mitler, M., and Mackie, R. (1996). Commercial Motor Vehicle Driver Fatigue and Alertness Study: Project Report (FHWA-MC-97-002). Washington, D.C.: Federal Highway Administration.
- Hanowski, R. J., Wierwille, W. W., Gellatly, A. G., Early, N., and Dingus, T. A. (1998). Impact of local/short haul operations on driver fatigue: Focus group summary and analysis. Report No. FWHA-MC-98-029. Washington, DC: U.S. Department of Transportation, Federal Highway Administration.
- Giam, G. (1997). Effects of Sleep Deprivation with Reference to Military Operations. Annals of Academic Medicine Singapore, 26, 88-93.
- Rhodes, W. and Gil, V. (2002). Fatigue Management Guide for Canadian Marine Pilots.
- Banks, S., Jackson, M., Van Dongen, H. (2012) Ch. 11: Neuroscience of Sleep and Circadian Rhythms. In The Handbook of Operator Fatigue. Matthews et al., (Eds.) Pgs. 263-296.
- Job, R., Graham, A., Sakashita, C., and Hatfield, J. (2012). Ch. 22: Fatigue and Road Safety: Identifying Crash involvement and addressing the problem within a safe systems approach. In The Handbook of Operator Fatigue. Matthews et al., (Eds.) Pgs. 349-363.
Nancy Grugle, Ph.D.
Human Factors & Ergonomics
Dr. Grugle is an expert in human factors. She has conducted research in several areas relevant to the effects of sleep deprivation on driver performance, including evaluating the effects of sleep deprivation on situational awareness and cognitive function, and testing the safety implications of distracted driving in work zones. Her research has been published in several scientific peer-reviewed journals.
Brooks is an experienced Transportation Manager specializing in trucking, warehousing, intermodal, and logistics related claims. After 13 years and 1.4 million miles as a CDL tractor trailer driver, Brooks spent the next 17 years in Transportation Management, holding the positions of Safety Instructor, Driver Recruiter, Safety & Risk Manager, Terminal Manager, and Regional Manager.