The first stage of fatigue is called hypovigilance. It is characterized by an impairment in sustained attention, decreasing the ability to detect signals in the environment. Hypovigilance is associated with mild dips in alertness, it initiates before the onset of drowsiness, and it is not physically felt. It is however likely to have critical safety implications, given that vigilance is central to the driving task. Hypovigilant drivers become inattentive, passive, less inclined to monitor the road environment, have slower reaction times, miss critical signals and are likely to show degraded tracking and speed management. Hypovigilance is always present when fatigue occurs. It is triggered by all the endogenous fatigue causes (i.e. sleep deficit, circadian cycle, time-awake since last sleep, medication, sleep apnea, etc.), but it is also associated with task monotony, low-demanding driving environments and increased driving automation (Managing commercial vehicle driver fatigue in Canada<\/a>.)<\/p>\n Continuing on the fatigue continuum, hypovigilance will progressively transition into drowsiness. Here the driver is becoming aware of fatigue, it is a physical experience, and one progressively needs to make efforts to remain in control of the task. At this point, vigilance is seriously degraded and so is driving performance (Hazard perception performance and visual scanning behaviours: the effect of sleepiness<\/a>.) If the driver remains at the task and no countermeasure is implemented, microsleeps are going to start occurring, first lasting a fraction of a second and progressively longer. Since drivers are not aware they are having microsleeps, the situation now presents critical risks as they are inclined to continue driving. Eventually the driver will fall asleep for good, most likely leading to a safety critical event. Fatigue-related crashes tend to involve single vehicles leaving the travel lane, without braking or other collision avoidance reactions. They tend to have serious consequences since impacts are often occurring at high speeds (Falling asleep whilst driving: are drivers aware of prior sleepiness?<\/a>.)<\/p>\n The fact that crashes are usually the result of the combined effects of several factors makes it challenging to determine how much fatigue contributes to crash events. For example, it is difficult for a police officer to determine, after the fact, if and to what extent hypovigilance or drowsiness were involved. Furthermore, drivers are either not aware that they were fatigued or not inclined (or available) to provide the information. As a result, databases relying on police reports tend to seriously understate the phenomenon (Understanding factors associated with misclassification of fatigue- related accidents in police record<\/a>.) In Canada, the National Collision Database (https:\/\/www.itf-oecd.org\/speed-crash-risk?utm_source=chatgpt.com), which is based on police reports, assesses that fatigue was involved in 3.3% of crashes in 2023, which is a significant under-estimation, but coherent with other comparable databases. Using a wider set of criteria based on an internationally accepted operational definition of fatigue-related crashes on the same dataset for the 2000-2003 period, a task force operating under CCMTA estimated fatigue contribution to fatal crashes at 19%. Moreover, multiple studies, using different methodologies, indicate that fatigue is a major contributory factor to road trauma (Bad behaviour or societal failure? Perceptions of the factors contributing to drivers' engagement in the fatal five driving behaviours<\/a>, Sleep deficiency and motor vehicle crash risk in the general population: a prospective cohort study<\/a>.) Fatigue is identified as a primary cause of road crashes for an average of 20% of all crashes in developed countries, 17% in Australia, and 25% in the UK (Sleep deficiency and motor vehicle crash risk in the general population: a prospective cohort study<\/a>.) In one survey, close to 80% of drivers reported that they had previously driven while sleepy (The association of schedule characteristics of heavy vehicle drivers with continuous eye-blink parameters of drowsiness<\/a>.) In other surveys, 66% reported having experienced driving while sleep (Age and gender comparisons of driving while sleepy: Behaviours and risk perceptions<\/a>.) Almost 33% of one sample of drivers surveyed had to fight sleepiness occasionally while driving and about 8% of the drivers reported occasional head nodding while driving (Symptoms of sleepiness while driving and their relationship to prior sleep, work and individual characteristics<\/a>.)<\/p>\n Obstructive sleep apnea (OSA) increases fatigue and is a highly prevalent disorder, estimated to affect up to 49% of men and 23% of women in the general population (Prevalence of sleep-disordered breathing in the general population: the HypnoLaus study<\/a>.)\u00a0One survey found that: 90% of OSA sufferers drove regularly; 72% drove between 1 and 20\u2009hours a week; 28% reported falling asleep while driving and 5% experienced a crash or near miss related to sleepiness within the previous five years (Driving consequences of sleepiness in Canadians with obstructive sleep apnea: A population survey<\/a>.)\u00a0Young drivers (18\u201324 years) appear to be over-represented in sleep-related crashes for several reasons related to late maturation of their brains\u2019 decision-making areas, slower reaction times while sleepy, lower tolerance for sleep loss than older adults, higher levels of sensation seeking and reactivity to monotony and greater vulnerability to sleep deprivation (Sleep deficiency and motor vehicle crash risk in the general population: a prospective cohort study<\/a>.)\u00a0Research on fatigue-related crash clusters has identified other vulnerable driver groups and patterns: afternoon fatigue crashes by middle-aged female drivers on urban multilane curves; crossover crashes by young drivers on low-speed roadways; crashes by male drivers during dark rainy conditions; pickup truck crashes in manufacturing \/ industrial areas; late-night crashes in business and residential districts, and heavy vehicle crashes (Understanding the drowsy driving crash patterns from correspondence regression analysis<\/a>.)<\/p>\n The most significant fatigue contributors are sleep deprivation related to acute or chronic sleep loss, extended wake duration, sleep fragmentation or sleep disturbances and low-demanding driving conditions (The association of schedule characteristics of heavy vehicle drivers with continuous eye-blink parameters of drowsiness<\/a>, Monotony of road environment and driver fatigue: A simulator study<\/a>.) Consequently, the most effective countermeasure against fatigue remains sleep. Studies show that sleeping only 6 hours per night was associated with a 33% increased crash risk, compared to sleeping 7 or 8 hours per night (Sleep deficiency and motor vehicle crash risk in the general population: a prospective cohort study<\/a>.)\u00a0Although drivers can identify that they are feeling drowsy, they appear to be poor at predicting when they will fall asleep (Awareness of sleepiness and ability to predict sleep onset: can drivers avoid falling asleep at the wheel?<\/a>) and appear to resist stopping to take breaks even when they have the opportunity to do so (Drowsiness and Decision Making During Long Drives: A Driving Simulation Study<\/a>.) Moreover, drivers cite multiple reasons for continuing to drive when they feel drowsy: time pressure, 27%; work requirements, 18%; failure to recognize impairment, 18%; necessity, 16%; shift work, 14%; long trips,13%, and; family and social expectations 10% (Bad behaviour or societal failure? Perceptions of the factors contributing to drivers' engagement in the fatal five driving behaviours<\/a>.) These reasons combined with a high cultural value for productivity, a social acceptance of fatigued driving, and the lack of a fatigue test create the perception that driver fatigue is not a significant problem (Bad behaviour or societal failure? Perceptions of the factors contributing to drivers' engagement in the fatal five driving behaviours<\/a>.)<\/p>\n Automated systems in new car technology, like intelligent cruise control, can increase fatigue through task underload and monotony (Vigilance decrement and passive fatigue caused by monotony in automated driving<\/a>, Road vehicle automation and its effects on fatigue, sleep, rest and recuperation<\/a>.) While driving without technological assistance can also be monotonous, monitoring an automated driving system can be equally or even more tedious and overreliance to technological safety assistance might also decrease drivers\u2019 vigilance to the driving task(Trust in automated driving: The sleeping pill of tomorrow?<\/a>.)<\/p>\n Driver fatigue countermeasures have been attempted with various degrees of success. The most effective are adhering to work-rest scheduling that permits sufficient sleep, driving primarily during the daytime rather than at night, respecting the two anticipated circadian lulls of the 24-hour day (mid-afternoon and from midnight to 6:00 am), obtaining adequate sleep immediately prior to a long trip, and taking fifteen-minute breaks every two hours during long road trips, and more frequently on monotonous roads. Consuming caffeine can provide short-term relief from drowsiness and rumble strips can alert drivers that they may be falling asleep, but these measures only provide temporary assistance. The most trustworthy countermeasures against driver fatigue are to obtain an adequate quality and quantity of sleep\u00a0and to exercise good judgment. In the words of Garry Sowerby, a world champion long-distance endurance driver, \"If you think you are too tired to drive, you are. Pull over and stop.\" (Road Fever<\/a>)<\/p>\n The issue of commercial vehicle drivers\u2019 fatigue has been studied at length. Drivers of heavy vehicle are exposed to all the main fatigue contributor: They work long hours, often spent in low-demanding monotonous road environments; they tend to accumulate acute and chronic fatigue over a work cycle; they operate during circadian low points during the night or mid-afternoon; there is a high level of OSA and other health issues that are associated with fatigue, and they tend to be paid by distance travelled, creating a motivation for them to work longer hours. In Canada, the situation is managed by means of a hybrid approach combining prescriptive rules (hours-of-service regulations) with a non-prescriptive voluntary fatigue management program based on the Fatigue Risk Management System (FRMS) model. The North American Fatigue Management Program (NAFMP) is an evidence-based program that offers comprehensive training and fatigue management tools to commercial vehicle drivers and motor carrier undertakings. It is available in both official languages, for free, at (Safe and Profitable Deliveries - NAFMP<\/a>.)<\/p>\n More information on drowsy-driving counter measures can be found at the following websites:<\/p>\n Drowsy Driving Overview - NHTSA<\/a><\/p>\nPrevalence:<\/h2>\n
Countermeasures:<\/h2>\n