Casr report series

Drivers with sleep disordered breathing have an increased risk of an accident.

16% of heavy vehicle drivers have both sleep disordered breathing and symptoms of excessive daytime sleepiness, both of which can be successfully treated.

A number of benefits were associated with the FMP:

Increased awareness of fatigue issues and management/prevention strategies.

Improved lifestyle

Reductions in the frequency of fatigue symptoms and the use of negative coping strategies.

Numerous business benefits including reductions in accidents and injuries, improved staff morale, and improved management and productivity.

The observed alertness effect was short lived and signs of sleepiness returned in 5 minutes following the hitting of the rumble strip.

Analysis of time of day of critical incident involvement identified a strong positive correlation to national traffic density data.

This study found that there was no increased risk of experiencing a critical incident from truck drivers driving in the 11th hour compared to the 10th or any other hour.

Regulated working hours may be inadequate for the following reasons:

Prescribed minimum breaks may be inadequate;

Requirements for short breaks are too rigid;

Regulations are inflexible;

TFMS provides scheduling flexibility for, but places few fatigue management obligations on, employers;

Regulations do not recognise the need for the active management of fatigue;

The focus of enforcement remains on drivers rather than those who influence or make scheduling decisions.

The paper also outlines compliance options, standard hours, BFM, AFM, chain of responsibility, code of practice, work diaries and record keeping, and enforcement aspects of the proposed changes to the regulations.

Most drivers reported that they experienced fatigue in the first 10 hours of driving.

Drivers experienced fatigue most often during the early morning and to a lesser extent in the early afternoon.

Factors that drivers identified as increasing fatigue included long driving hours and problems associated with loading and unloading (particularly delays).

Strategies drivers reported as most effective for managing fatigue include: sleep, rest, drinks containing caffeine, and “stay-awake” drugs.

Fewer drivers in the current survey reported using “stay-awake” drugs.

Owner-drivers do longer trips but appear to have greater flexibility over trip scheduling.

Fatigue-related incidents are common occurrences for long distance drivers.

Drivers most commonly broke working hours regulations due to work organisational and reward factors.

Drivers paid in terms of the amount of work they did reported more fatigue than drivers paid at an hourly rate.

The survey demonstrated little change in the working conditions of long distance truck drivers between 1991 and 2001 although awareness of fatigue appears to have improved and the occurrence of fatigue has reduced.

Half of the companies surveyed reported that fatigue was well managed and 20% reported that it was badly managed. It appears that drivers knowledge and awareness of fatigue issues is much better than the companies that employ them.

The majority of companies reported having considerable control over work schedules with strict estimated times of arrival being uncommon.

Companies reported less intervention and active management of fatigue for non-employee drivers.

The survey suggests that there is considerable scope for improving the understanding and management of fatigue in the industry.

While many drivers report experiencing fatigue related issues when driving, very few drivers consider fatigue to be more than a minor problem for them.

Long working hours was considered one of the most important contributors to fatigue. Other factors included irregular or inadequate sleep and other aspects of work such as having to stick to regulations, and heavy traffic.

40% of drivers reported occasionally driving contrary to regulations.

Driving without taking breaks was influenced by driving schedules and conditions, and the drivers’ motivations to make money.

Common reasons for not stopping for a break included scheduling and practical (e.g., nowhere to stop the truck) limitations.

Perceptions that fatigue is well managed in the industry have increased.

Improvements in the implementation of formal fatigue and medical policies to include subcontractors, etc.

Perceptions of increased awareness of driver fatigue within the industry were lower than those observed in 1998.

Improvements in knowledge regarding causes of fatigue and effective fatigue management strategies.

Improvements in the determination of trip times.

Enabling the use of EWDs will present stakeholders with numerous opportunities in other areas such as the generation of management reports or the introduction of non-roadside enforcement practices.

The blue reflectors are used in a number of Australian states and are recognised by the heavy vehicle industry.

High levels of fatigue and sleepiness were also observed.

Individuals who are sleep deprived are not always aware of the severity of their impairment.

Some individuals may be genetically predisposed to the cognitive impairments associated with sleep loss.

Biological clock generates the circadian rhythm which effects sleepiness levels. Extended wakefulness also leads to sleepiness and the increased likelihood of falling asleep.

Time-on-task can lead to increased cognitive impairment, this fatigue effect is more prominent after sleep deprivation.

The cognitive impairments due to sleep loss are often highly variable both within individuals and between individuals.

Time-on-task also increased with increasing impairment.

Micro sleeps were relatively common in the late afternoon and an increase in micro sleeps was strongly correlated with an increase in crashes.

Fatigue was involved in 16% of all fatal crashes and 9% of all injury crashes in NSW in 2008.

Regardless of fatigue, 0.8% of all crashes were fatal, however 2% of all fatigue related crashes were fatal in NSW in 2008.

Impairments in psychomotor vigilance, working memory and cognitive throughput were found after chronically restricting sleep to 4 and 6 hours per night.

Participants did not adapt to chronic partial sleep deprivation, after 14 days, cognitive deficits were comparable to those after 1 to 2 days of total sleep deprivation.

Subjective sleepiness ratings were greater after total sleep deprivation and initially after chronic partial sleep deprivation, however, these ratings showed adaption to the chronic partial sleep deprivation. That is, after 14 days of chronic partial sleep deprivation, cognitive performance was at it’s worst, however participants reported only feeling slightly sleepy.

After chronic sleep restriction, participants spent less time in stages 1, 2, and REM sleep.

Those who naturally sleep longer may be more affected by 14 days of sleep deprivation.

In 1987 to 1992 inclusive, 16% of all crashes in which police were called in southwest England were found to be sleep related. Three peaks in sleep related crashes were found, 2-3am, 6-7am, and 4-5pm.

23% of all crashes on motorways in the midlands during August 1991 and 1992, and April 1994 were sleep related. There was a peak in sleep-related crashes between 12am-3am and during the mid-afternoon.

Sleep related crashes can occur even after a short period of driving due to the influence of the circadian rhythm.

Crash reports suggested only 5.1% of truck crashes in New Zealand during 2001 and 2002 involved fatigue. However, when other factors were considered, such as physiological risk factors and the driver’s opinion of fatigue involvement, 17.6% of crashes were classified as fatigue related.

Somewhere between 29-59% of fatigue related crashes may not be classified as fatigue related on crash reports.

By stopping driving when drivers are fighting sleep, using highway rest stops, drinking coffee, using the radio, getting at least nine hours sleep in the 48 hours prior to a trip, and avoiding long distances or sharing driving may reduce risk of crash.

Drivers who felt they were sleepy, reported less than five hours sleep (compared to those reporting more than five hours) in the preceding 24 hours, and those driving between 2-5am were at greater risk of crash.

Chronic sleepiness was not associated with an increase in crash risk.

Risk factors for a fatigue related incident may be due to tiredness due to sleep loss, late night driving, and shift-working.

City fatigue related driving incidents tended to occur on work trips or commuting to and from work, as well as social trips.

By the second night of sleep deprivation participants produced increased errors of omission

Both of these impairments returned to normal after one night of recovery sleep

During sleep deprivation, speed and lapses remained at baseline levels for the nine hour group. For the seven hour group there was an initial reduction in psychomotor speed which then stabilised at a slowed rate. The effect was similar for the five hour sleep restriction group however this group also experienced greater numbers of psychomotor lapses. The three hour group had increasingly slower reaction times and greater numbers of lapses over the seven days of sleep restriction.

During recovery sleep, there was no evidence of recovery found in the five or seven hour sleep restriction group. Impairment in speed and lapses in the three hour group recovered after one night of recovery sleep however they did not recover to baseline levels, rather they stabilised at a level of impairment similar to the five and seven hour group.

Recovery from chronic partial sleep restriction is not as rapid as that of total sleep deprivation.

The more complex tasks in the study were more sensitive to the effects of fatigue compared to the relatively simpler tasks.

After 20 hours of sustained wakefulness, performance impairment was equivalent to a BAC of 0.10%.

Performance impairment after 24 hours of sustained wakefulness corresponded with the impairments found at a BAC of 0.05.

Increased reaction times were found with sustained wakefulness, while performance on psychomotor tasks also increased in variability,

Sleep deprivation impaired performance in most cognitive domains.

Simple attention and vigilance was most affected by sleep deprivation.

Complex attention and working memory tasks were only moderately affected by sleep deprivation.

Accuracy of reasoning and crystallised intelligence were not influenced by sleep deprivation.

Sleep deprivation differentially effects the various cognitive domains but does not bias people to respond faster or more accurately.

Age did not influence this impairment.

After a night of sleep deprivation the younger participants produced slower reaction times but the older participants’ reaction times remained unaffected.

There was no difference found in objective sleepiness measures during the driving task between the groups.

Both subjective and objective sleepiness measures showed the drivers were less alert and more sleepy during the evening compared to the afternoon simulated driving session.

With less traffic during the simulated tasks there was greater objective sleepiness.

Crashes seemed to be preceded by two phases of changes in steering wheel use behaviour. Firstly, lane keeping and steering control variables were affected. The second phase involved ‘dosing off’ in which the steering angle was constant and there was no input from the driver. Run off road crashes were associated with this latter phase.

There are individual differences which suggest drowsiness detection systems based on changes in steering wheel behaviour may fail to issue warnings for some drivers or in some situations, whereas in other cases they may give false alarms.

The truck drivers reported an average of approximately 7 hours sleep in the previous 24 hours.

Fatigue was considered a greater problem for other drivers than themselves and only 63% of the truck drivers stated that fatigue was ‘always’ dangerous for drivers.

The researchers suggested that older drivers may be more susceptible to fatigue related impairment

Age and length of prior rest/sleep predicted failure rates on the driving simulator.

The researchers did not directly study this but suggested professional drivers may be less susceptible to fatigue impairment due to their greater driving experience.

The researchers suggested at the time of the study, the current regulations for service hours were not effective in managing fatigue or driver compliance.

The researchers suggested the knowledge that a monotonous trip is soon to be completed may make drivers feel their vigilance levels have improved while their actual state of vigilance continues to become increasingly impaired with continued driving.

The most common illicit drug used by the drivers was amphetamines.

Fatigue symptoms show large individual differences

Driving performance impairments due to fatigue were found to relate to the road environment, that is, not the same impairments were found in curved and straight roads.

By monitoring and managing their own state, as well as actively avoiding situations which can lead to stress, may lead to slower fatigue development. Continuously re-evaluating situations may also be able to aid in this way, as well as allowing for better time management to allow for rest breaks and avoid feeling pressure to drive while fatigued to make up lost time.

Inexperienced drivers may be so preoccupied with deadlines that they may not be in a psychological state which allows them to re-evaluate the situation compared to experienced drivers.

Fatigue-related driver training may benefit from including, not only basic time management principles, but also relevant work-related planning in the context of issues that often occur in the daily life of truck drivers on the job.

An ESS score greater than 10 lead drivers to be at three times greater the risk of falling asleep at the wheel.

Those truck drivers who reported greater than six hours night-time driving were four times as likely to fall asleep at the wheel compared to those reporting fewer hours.

Working more than 13 hours lead to 2.5 times the risk of falling asleep while driving compared to those who worked less than 13 hours in a 24-hour period.

Those truck drivers using medications were nearly five times more likely to fall asleep while driving.

Years of experience was not related to an increase in risk of falling asleep, nor was driving solo compared to driving with a partner at least 50% of the time.

The researchers noted that there is inconsistent evidence on the age-related effects of fatigue on crash risk, however larger studies suggest that younger drivers may be at greater risk, suggesting that younger drivers may be more suited to short haul driving.

Endogenous variables with the potential to influence fatigue included: genetic factors, gender, age, race, nutrition, BMI, endurance (both mental and physical), circadian strength, chronotype, phase and desynchrony, personality, sleep requirement and debt, and health status (physical and psychological).

Exogenous variables with the potential to influence fatigue included: Working arrangements, time and method of commuting, physical and cognitive state at commencement of shift, the start time and duration of the shift, workload, motivation, time since last sleep, quality and duration of sleep, napping, recovery time between shifts, meal timing and content, work conditions, medication and drug use, job control, monotony, and so on.

More articulated compared to non-articulated trucks were involved in fatigue related crashes.

Inconsistent definitions of fatigue makes the involvement of fatigue in crashes difficult to determine.

The potential role of fatigue can also be difficult to determine post-crash.

Furthermore, the assumptions underlying the models in terms of the relationship between these variables, other sleep-related variables and performance requires further validation.

The researchers noted that the ability for the CAS to use individual data in predictions is commendable.

Evaluating warning strategies is important because if a fatigued driver does not respond appropriately to the warning, there is no safety benefit in using the technology.

Evaluation of warning strategies should be conducted in different contexts, laboratory studies provide the ability for researchers to control confounding variables, but they may lead to differing results compared to naturalistic settings. Therefore, despite the disadvantage of lack of control, naturalistic studies are also highly important.

In-vehicle countermeasures were considered superior to on-road countermeasures as they allow rapid detection of any sudden changes in alertness and they operate constantly.

On-road countermeasures such as rumble strips may be effective but they are relatively expensive so their deployment can only be in specific high crash locations (therefore their benefit is not constant throughout a trip).

In-vehicle countermeasures could be dangerous if drivers rely too heavily on these devices to alert them of when their driving is impaired.

Analysis of steering patterns may be particularly valid compared to other measures while eye closure and head nodding measures may also have potential.

Driver strategies such as playing alerting games need to be further evaluated.

There is little evidence that introducing cold air to the driving environment will reduce fatigue, that is, unless the driving environment is particularly hot.

An effective system will rarely produce false alarms, or give warning too late, it will not be overly intrusive and should be sensitive to all levels of fatigue (not simply extreme fatigue)

Using individualised data is also beneficial in fatigue detection technologies.

Challenges for the technologies were considered including the ratio of misses and false alarms and intrusiveness.

Operator compliance and reliance are also issues which technologies must overcome.

Head nodding technologies received very low scores due to numerous false alarms and misses.

ASTiD and Optalert were the only two technologies recommended by the researchers for fatigue detection.

There were clear differences in the causes of fatigue for the two types of driver. Short haul drivers worked long hours with a significant number of deliveries and pick ups, and had to deal with heavy urban traffic. Long haul drivers also worked long hours, however spent more time waiting for loading and unloading, and participated in more monotonous rural driving.

The nature of fatigue-related incidents is determined by the demands of the driving environment. Rural and urban environments present different demands.

Short haul drivers were less likely to view fatigue as a problem for the industry than were long haul drivers.

There is a need to reduce fatigue causing factors within the short and long haul transport sectors. There is also a need to raise awareness of driver fatigue issues for short haul drivers.

Discusses the use of roadside testing procedures to reduce the incidence of drug and alcohol use by drivers.

Compares the advantages and limitations of methods used in Australia and in other countries.

The largest number of positive findings (9.5%) were for stimulants such as methamphetamine, amphetamines, ephedrine/pseudoephedrine, and cocaine.

The second most common drug was cannabis (4.3%).

1.3% of drivers tested positive for alcohol.

25% were cocaine, and 12% were cannabinoids.

Interstate driver use more prescription and illicit drugs to stay awake while intrastate drivers rely more on over the counter medications.;

The most frequent methods for obtaining stimulant drugs were through a doctor, a chemist, or illegal prescription.

A significant proportion of drivers reported stimulant use as a helpful fatigue management strategy.

Drivers who had the greatest problem managing fatigue were twice as likely to use stimulants.

Drivers paid on a payment-by-results or contingency payment basis were 2-3 times more likely to use stimulants.

Younger, less experienced drivers were also more likely to use drugs.

This study demonstrates the influence of external factors, particularly productivity-based payment systems, on the stimulant drug use of truck drivers.

Some drivers begin using drugs before they begin driving trucks.

Apart from fatigue motivations for drug use included peer pressure, socialisation, relaxation, addiction, and wanting to fit the trucking “image”.