Research gaps and needs for preventing worker fatigue in the transportation and utilities industries

Abstract

Background:

The transportation and utilities industries include establishments engaged in the movement of passengers and freight, or the provision of public power, water, and other services. Along with the warehousing industry, they make up the US National Occupational Research Agenda’s Transportation, Warehousing and Utilities (TWU) industry sector. In 2018 the sector composed 5% of the US workforce, with approximately 8 million workers. TWU workers experienced 19% of all fatalities among U.S. workers in 2018 and 7% of total occupational injuries and illnesses.

Methods:

Around-the-clock operations, heavy workloads, long and irregular shifts, complicated schedules, and time pressures characterize work across the US TWU sector. However, there are considerable differences in worker priorities and concerns between TWU industries. Major areas of concern within the sector include disparities in work schedules; required training for employee fatigue awareness and prevention; physical and mental job demands; and safety culture.

Results:

Strategies for fatigue mitigation are critical to reduce the prevalence of injuries, safety-critical events, and crashes in TWU workers. Further research on the incidence and characterization of fatigue among TWU workers will guide the development of effective mitigation strategies. The influence of work scheduling on missed sleep opportunities and disrupted circadian rhythms should be determined. Evaluation of fatigue mitigation strategies can lead to the adoption of the most effective ones for each TWU industry.

Conclusion:

Implementation of effective strategies is critical for the health, safety, wellbeing, and productivity of workers in the TWU sector.

1 |. INTRODUCTION

The transportation and utilities industries include establishments engaged in the movement of passengers and freight, or the provision of public power, water, and other services. Along with the warehousing industry, they make up the US National Occupational Research Agenda’s Transportation, Warehousing and Utilities (TWU) industry sector. In 2018 the sector composed 5% of the US workforce, with approximately eight million workers.¹ TWU workers experienced 19% of all fatalities among US workers in 2018 and 7% of total occupational injuries and illnesses.¹

Around-the-clock operations, heavy workloads, long and irregular shifts, complicated and varying schedules, and time pressures characterize work across the US TWU sector. However, there are considerable differences in worker priorities and concerns across TWU industries. Major areas of concern within the sector include disparities in work schedules; required training for employee fatigue awareness and prevention; physical and mental job demands; and safety culture.

The Working Hours, Sleep and Fatigue Forum² hosted by the US National Institute for Occupational Safety and Health (NIOSH) in September 2019 facilitated discussion of research gaps and needs around working hours, sleep, and fatigue specific to seven US industry sectors. This paper describes those findings for workers in the US transportation and utilities industries. It is not meant to be an exhaustive literature review, but rather, a description of the broad research on these concerns within the TWU sector. Recommendations for additional research are provided. Due to the paucity of research on work hours, sleep, and fatigue in the warehousing industry, this paper covers findings only in the US transportation and utilities industries of the TWU sector.

2 |. FATIGUE IN TRANSPORTATION INDUSTRIES

2.1 |. Air

Extensive research has been conducted on pilot fatigue,^3–12 particularly in aviation operations involving long-haul or ultra-long-haul routes,^13–17 and on jet lag and circadian rhythm disruption.^18–22 Fatigue awareness and prevention strategies have also been studied in airline pilots,^23–29 often with an emphasis on proactively identifying, managing, and mitigating fatigue.^30–33 However, fatigue in pilots flying for commuter and on-demand operations (14 CFR Part 135) and general aviation operations (14 CFR Part 91), has not been as exhaustively researched. These latter operations encompass a wide variety of aircraft, workload demands, flight environments, and missions. In addition to pilots, air traffic controllers and maintenance personnel who perform safety-critical functions are often impaired by fatigue stemming from insufficient or poor-quality sleep, circadian rhythm disruptions, and long duty periods.^24,34–36 Flight attendants have reported a higher prevalence of fatigue than the general population³⁷ and have been the subject of research on fatigue prevention training and comparison of international fatigue regulations. Regulations for working and rest hours for flight attendants in the United States were found to be among the least restrictive, and allowed a greater-than-typical risk of fatigue.^38–40

Federal aviation regulations address fatigue management for pilots and flight attendants of large, passenger-carrying commercial aircraft by prescribing flight time limitations and required rest periods (14 CFR Part 117; 14 CFR § 121.467). Regulations do not provide similarly stringent limitations on work and rest hours for maintenance technicians who repair aircraft (14 CFR §121.377), although fatigue among maintenance workers has been linked to fatal aircraft crashes.³⁴ Mitigation strategies such as policies to reduce unexpected roster changes, decrease the frequency of individuals working longer than their rostered shifts, limit the hours of service (HOS), implement fatigue risk management systems, and education on fatigue causes, consequences, and countermeasures may limit the incidence of fatigue and fatigue-related maintenance errors and improve safety in aviation operations.^41,42

2.2 |. Trucking

The Federal Motor Carrier Safety Administration (FMCSA) has reported that driver fatigue has been identified as an important factor in large truck crashes.⁴³ However, estimates of the prevalence of crashes involving driver fatigue vary greatly due to different reporting practices and data sources.⁴⁴ In addition, driver fatigue can be difficult to identify during crash investigations, or investigators may not be trained to recognize signs of driver fatigue (e.g., lack of skid marks on the road behind an accident).⁴⁴

A wide range in estimates in truck-driver-related motor vehicle crashes have been reported in the literature. Knipling and Wang⁴⁵ studied 1989–1993 General Estimates System (GES) and Fatality Analysis Reporting System (FARS) data of motor vehicle crash investigations based on police reports. The authors estimated that 1.4% of nonfatal crashes and 3.6% of fatal crashes were associated with driver drowsiness/fatigue (including both truck and passenger vehicle crashes). A study of 2018 FARS data suggested that 1.3% of fatal large truck crashes were attributed to truck driver sleepiness or fatigue.⁴⁶ While police investigations included in FARS data are one viable source of data for motor vehicle crashes, they may be an underestimation of the true prevalence of fatigue-related crashes since driver fatigue can be difficult to detect.⁴⁴

The National Transportation Safety Board (NTSB) found that fatigue was the most frequently cited probable cause (31%) in fatal-to-truck-driver heavy truck crashes among 182 crash reports occurring in eight states between October 1, 1987, and September 30, 1988.⁴⁷ However, since fatal-to-truck-driver crashes represent only a small portion (approximately 18%)⁴⁸ of fatal large truck crashes, the NTSB estimate should not be applied to all fatal large truck crashes.⁴⁴ FMCSA’s Large Truck Crash Causation Study (LTCCS) investigations of 963 fatal and nonfatal large truck crashes estimated that truck driver fatigue was judged to be present in 13% of truck crashes.^49,50 Of all LTCCS crashes where the truck was at-fault, asleep-at-the-wheel was the critical reason (CR), or immediate reason for the crash, in 7%.⁵⁰ As a percentage of all LTCCS crashes, truck driver asleep was the CR in 4%.⁵⁰ For all LTCCS multi-vehicle crashes where another vehicle was assigned the CR, as well as the critical event leading to the crash, asleep, was the CR in 9%.⁵⁰ In all, 8% of LTCCS crashes had a CR of asleep, assigned either to the truck driver or another driver.⁵⁰ A National Academies of Science, Engineering, and Medicine review of available data and studies reported that among the approximately 4000 fatalities resulting from crashes involving trucks and buses in the United States each year, 10%–20% of these crashes may have involved fatigued drivers.⁴⁴

Commercial truck drivers, particularly those in long-haul freight delivery jobs, often operate in a work environment with multiple factors that are associated with lack of sleep, fatigue, and stress.⁵¹ Insufficient sleep is associated with impaired cognitive performance, slowed reaction times, increased risk-taking behavior, and decreased overall driver situational awareness, increasing drivers’ risk for fatigue-related crashes.⁵² Fatigue is often related to work schedules, including long work hours, irregular work shifts, and being away from home for days or weeks at a time.⁵³ Driver schedules, and consequently time awake and on task, can be extended due to factors such as delays in loading and unloading, weather conditions, and traffic.^54–58 Time-pressured delivery commitments can increase driver stress and fatigue.^54,59–65 As a part of their workday, many commercial truck drivers engage in considerable physical activity when they are not actually driving, such as loading or unloading their own trucks (e.g., making grocery deliveries to stores, moving household goods, and many others). At times, such physical activity can offer a stimulating effect to promote subsequent driving alertness; whereas in other instances such strenuous work can be tiring (both physiologically and cognitively) and hasten the onset of fatigued driving.^66,67 Additionally, drivers are often paid by the mile driven instead of by hours worked, creating psychological stress and pressures to push their hours of work.^68–70

While driving and rest times are regulated by FMCSA hours of ervice (HOS) regulations (49 CFR Part 395), there are individual-level factors among truck drivers which increase the risk for fatigue-related crashes. Long-haul truck drivers have a high prevalence of obesity (69%), hypertension (26%), and diabetes (14%),^60,71–74 all of which tend to be comorbid with the high prevalence (at least 21%) of obstructive sleep apnea (OSA), a sleep disorder associated with driver fatigue.^75,76 One of the most significant remaining research gaps is the need to identify the true incidence rate of OSA and to develop proactive strategies for resultant sleep-deprivation and driver fatigue.⁴⁴ There are also individual differences in susceptibility to fatigue due to age, gender, alcohol consumption, and personal traits.⁷⁷ Males and young drivers are at higher risk of fatigue than their counterparts. Further development of methods to identify individual differences in fatigue susceptibility is needed.⁷⁸

2.3 |. Urban transit and ground passenger

The transit industry provides service from early morning to late night, often with 24-h service, to meet the needs of the public ridership. Ground passenger transportation provides on-demand service (e.g., taxis or uber-like transportation) with demands that bridge the gap between what is offered by public transit and the passengers’ specific destinations. Bus drivers working as fill-ins or substitutes for extra board or on-call often get little time off between assignments for rest. Many public transit agencies require bus and train operators to work split shifts. Transit operator fatigue management programs are not systematically applied and their operation needs to be reinforced repeatedly by agencies.⁷⁹ The Bureau of Labor Statistics finds that transportation-related incidents are the leading cause of fatalities (55%) in the urban transit and ground passenger industry in the United States.⁸⁰ Little data are available to quantify the burden of fatigue on fatalities. Blower and Green⁸¹ noted that being drowsy or asleep was only noted as a driver error in 1.1% of 2252 fatal bus crashes between 1999 and 2005. Bus driver fatigue was cited only once as an associated factor in 40 fatal bus accidents included in the Bus Crash Causation Study.⁸²

International studies of taxi drivers and other passenger drivers-for-hire focus on the prevalence of fatigue-related outcomes (e.g., driving while tired, motor vehicle collisions) and risk factor identification. Established epidemiologic associations are between fatigue and motor vehicle collisions or near misses,^83–90 with shift timing,^89,90 length of working time,^87–94 and insufficient rest periods^87,90,91,95 the most frequently identified risk factors. Other risk factors include pay structure,⁸⁹ caffeine use,^90,92 optimism bias where drivers are unaware of their fatigue level,^{86,91 95} deficient sleep time or quality,^88,92 working an additional job,⁹² poor safety climate, high perceived job demands, and workplace violence⁹⁴ and emotional demands.⁹⁶

The starting point for addressing fatigue-related risks are HOS limitations for passenger-carrying vehicles, including buses, that are set by federal regulation (49 CFR Part 395). Published studies on bus operator fatigue are focused on work shifts and fatigue-related outcomes, specifically, epidemiologic associations between split shifts and alertness,⁹⁷ drowsiness,⁹⁷ sleepiness^97,98 and fatigue,⁹⁸ alternating shifts and sleepiness,^99,100 night shifts, working hours, and motor vehicle collisions,¹⁰¹ and shift work, working hours, and fatigue (with a calculated risk index).¹⁰⁰ Research examining fatigue as a risk factor for motor vehicle collisions^102,103 and sleep disorders^104,105 is also found in the scientific literature.

The ground transportation industry is less regulated with respect to fatigue prevention or mitigation. HOS limitations are generally the starting point for best practices. Fatigue mitigation is limited to HOS and is typically promulgated at the municipal level, with a focus on limiting drivers to a maximum of work hours per shift over a 7-day workweek. To the knowledge of the authors epidemiologic research evaluating the effectiveness of HOS laws is not available in the scientific literature.

2.4 |. Rail

Federal regulations provide for HOS limitations for workers in train or engine service (engineers, trainmen, hostlers, conductors, etc.) (49 CFR § 228.11) and for train operators for commuter or intercity passenger operations (49 CFR § 228.405). Rail operators frequently have inadequate rest or sleep from commuting between their place of work and their homes. Operators on extra board on-call status accumulate more overtime and, ultimately, more sleep loss and fatigue. Research suggests railroad workers with fatigue have an increased risk of human-factors-related incidents (e.g., collisions, derailments, near misses, or missing signals).^79,106,107 Workers in railroad dispatching centers may be in regular, relief, or extra board job status, and are also subject to fatigue.¹⁰⁸

The US railroad industry aims to manage fatigue-related risk in operations through a combination of educational efforts, adjustments to work schedules, sleep disorder screening programs, collaborations in development of biomathematical models of fatigue and alertness,¹⁰⁸ and experimentation with technological aids to fatigue management.^109,110

2.5 |. Seafaring and inland waterways

Seafaring is an isolated and confined work environment on a 24-h work schedule which can affect the mental state and physical fatigue experienced by workers at sea.¹¹¹ Fatigue has been implicated in 16% of vessel accidents and 33% of personal injury accidents.¹¹¹ Crewmembers on vessels subject to US manning requirements must receive a minimum of 10 h rest in any 24 h (46 CFR.15.1111).

There is a paucity of studies of workers on passenger or freight-carrying seafaring commercial vessels and fatigue. For decades, the US Navy conducted research into alternative crew watch schedules, examined sleep patterns of sailors aboard Navy warships and submarines, and attempted to shift the timing of sleep to ensure alert and safe operations at sea.¹¹² Crew numbers become smaller as new ship design and automation technologies advance, affecting sailor workload and cognitive fatigue from the vigilance required when working around automated technologies. Although the work has modernized, the issues relating to fatigue and safety remain, and research in this field continues to be warranted.

The U.S. Coast Guard (USCG) promotes HOS limits for Inland Waterways Towboat and Barge Operations (US Code 8904c). Towboat crews generally stay on board for about 28 days of continuous operations, followed by 2 weeks off-duty. A preferred practice is for crews to alternate 6-h shifts (square watch system of 6-on, 6-off, 6-on, 6-off), for totals of 12-h on-duty and 12-h off each 24-h day, and employing a split-sleep schedule. While published research on the health of towboat and barge shipping workers is not available, obesity has been found to be prevalent among wheelhouse crew.¹¹³ The USCG developed a Crew Endurance Management System to identify and manage operational risk factors, although few carriers take advantage of it.¹¹⁴ The system evaluates crew endurance and management through a range of environmental, physiological, operational, and psychological risk factors such as irregular work periods, temperature extremes, heavy workloads, and extended separation from family members,^115,116 and provides light-management techniques to match energy levels with time-of-day, practical recommendations for controlling operational risk factors, and guidance on plan design and implementation.¹¹⁴

2.6 |. Fatigue in the utilities industry

Split, weekend, and night shifts are common for utilities workers who may experience long shifts (longer than 8-h) and extended working hours (longer than 10-h). Many of these workers work on-call to fill in shifts, especially during emergency operations. Little warning or time to plan rest or recovery periods often results in varying sleep duration and timing. Shift work, especially rotating shift schedules, and the incumbent difficulties caused by circadian biological disruptions readily lead to poorer performance.¹¹⁷ Rosa and Bonnet¹¹⁸ found that after 10 months adaptation from an 8-h/5–7-day shift schedule to a 12-h/2–4-day (8 or 12-h rotating day and night schedules) shift schedule, workers in a natural gas utility reported higher subjective workloads on 12-h shifts compared to 8-h shifts. More frequent reaction time misses and hand tremors among these workers seen during the 12-h shifts were considered attributable to the extra 4-h on the extended shift.¹¹⁸ Measures of circadian fluctuations in performance and subjective state showed decreases at night, with the worst performances after the 12-h shift schedule. Extra caution was recommended when scheduling critical activities during extended work shifts, especially night shifts, with attention given to staffing levels, workload, job rotation, environmental exposures, emergency contingencies, rest breaks, commuting time, and social/domestic responsibilities.¹¹⁹

Additional risk factors for fatigue among utilities workers are long commutes from home or to distant work sites in times of emergency and for restoration of utility services.¹²⁰ Fatigue may compound other hazards, since workers often deal with dangerous agents and conditions such as electricity, natural gas, chemicals, hazardous waste, extreme heights, or extreme weather conditions. A survey of electrical transmission and distribution-line construction workers found extreme temperatures and long shifts were perceived as principal causes of fatigue.¹²¹ These results suggest that findings from fatigue-laboratory research may not directly apply to utility workers’ perceptions of causes of fatigue. The joint effects of fatigue and working in extreme temperatures as well as in diverse or unfamiliar surroundings should be evaluated.

In the nuclear power industry, maintaining alertness for control room operators at all times is critical. Factors affecting operator performance include shift schedules, caffeine and alcohol use, diet, family lifestyle factors, control room working environment, staffing and overtime practices, and work task design.¹²² In a study of five safety indicators among nuclear plant workers, operator overtime was found to be significantly related to plant safety performance but use of a 12-h shift schedule was correlated only with one metric, operator error.¹²³ The US Nuclear Regulatory Commission recognizes operator fatigue in the nuclear power industry and has developed guides for managing personnel fatigue.^124–126

Further delineation of the influence of work hours and worker fatigue is warranted in this subsector. Reliable data are limited and there is a need for broader research concerning utilities workers and adequate sleep, work shift length, and involuntary overtime; assessment of environmental factors such as high temperatures in the workplace; and the incidence of heavy workloads.

2.7 |. Research needs to reduce fatigue risks

The NIOSH Working Hours, Sleep and Fatigue Forum identified disparate research gaps and needs within the US TWU sector.

2.8 |. Data needs

Surveillance studies provide baseline data on the incidence of fatigue and associated risk factors. Fatigue identified in workers such as aviation maintenance technicians, seafarers, transit drivers, utilities workers, bus and truck drivers, and warehouse workers need further examination. Baseline studies for these occupations can determine the contribution of operator fatigue to work performance and safety. They also will provide data for evaluation of approaches to managing fatigue-related safety risks.^127,128

2.9 |. Specific issues

The impact of the working environment on fatigue should be evaluated. Contributors within the work environment include long or irregular work hours; extended and variable work schedules; time pressure; work in diverse or unfamiliar surroundings; environmental conditions; and psychological stress such as time away from home.⁵³ Long hours and shifts may exacerbate physical and mental health disorders or disrupt circadian rhythms, which can affect sleep and increase worker fatigue. Kudo and Belzer¹²⁹ note that the relationship between employment attributes, such as method and level of compensation, and worker fatigue is not well understood. Pressures from gig work, where workers such as couriers are paid on a piece-rate or “gig,” may cause anxiety and fatigue from greater physical and mental workloads in the 24/7 economy.^130,131

Many factors that cause or contribute to fatigue occur in combination in TWU workers. Mitigation of all possible causes of fatigue may not be feasible. Control of many of the predominant risk factors or groups may be more feasible. Efforts to develop tools for detecting and measuring drowsiness have advanced and should continue.^132–134

The emergence of onboard safety monitoring systems including real-time fatigue detection technologies and mandatory use of electronic logging devices in the United States (effective on December 16, 2019) provide new opportunities to measure driving time and truck driver fatigue objectively and in real-time. Most previous studies used self-report data to measure driver fatigue and driver time. The onboard fatigue and behavior measurement technologies use machine learning and pattern recognition technologies to detect fatigued and distracted driving behaviors. The technologies can also provide feedback to drivers and managers, which can potentially reduce fatigued driving.^132–134 The FMCSA is planning to employ data that are collected from onboard safety monitoring systems in its updated study of contributing factors to crashes involving large commercial trucks.¹³⁵

Better understanding of diagnosis and treatment for OSA can help to develop best practices for detection and treatment of OSA. OSA varies in terms of severity on a continuum from mild to moderate to severe apnea. It is not clear how apnea impacts operator fatigue, and to what degree. More research is needed to determine at what point (i.e., diagnosed mild, moderate, or severe apnea) safety preventive measures (such as continuous positive airway pressure (CPAP)) should be imposed.

2.10 |. Program evaluation and implementation needs

Fatigue mitigation in industries such as aviation, trucking, and rail transportation has been accomplished with regulated HOS or duty, and rest times. The effectiveness of this approach should be determined. An alternative means of compliance to HOS has been development of Fatigue Risk Mitigation Systems (FRMS). FRMS guidelines are proposed by the operator rather than by regulation. FRMS are considered better aligned with overall system performance.¹²⁷ Gander et al.¹²⁷ point out that a FRMS or endurance management systems can determine not only how fatigue affects safety, but also may help to build a business case for such a system. Fatigue risk management guidelines and fatigue management strategies are being developed for the utilities industry.^136,137 They are already in use for some occupations in air,^138–140 ground,^141,142 and sea transportation.¹¹⁴ Implementation of fatigue management systems or other successful interventions should be encouraged in other industries.^143,144 Other tools to address causes and consequences of fatigue may include wellness programs, fatigue self-assessment, and fatigue prevention training in organizational health and welfare programs. These tools can inform organizational safety culture and fatigue management policy.

Barriers to implementation of an effective FRMS should also be determined. Changes in fatigue levels due to fatigue management as well as organizational benefits, worker acceptance, process changes, and costs should be considered. An example is the evaluation of the effectiveness of the North American Fatigue Management program (NAFMP) in reducing commercial truck driver fatigue.⁴² The NAFMP (www.nafmp.org) was designed to enhance carriers’ and drivers’ ability to effectively deal with the challenges of fatigue through training, use of technologies, sleep disorder screening and treatment. The NAFMP was developed by international partnerships between multiple jurisdictions (FMCSA and Transport Canada) and motor carrier stakeholder groups. NIOSH is conducting a longitudinal observational cohort study to evaluate the effectiveness of NAFMP in reducing commercial truck driver fatigue.

Implementation, evaluation, and dissemination of best practices for an effective fatigue mitigation plan will improve health and safety for all TWU workers. Sharing guidance and evidence-based solutions from such studies will allow for broader support for fatigue mitigation FRMS systems, and allow policymakers, regulators, management, and workers to adopt and implement fatigue mitigation strategies.

3 |. CONCLUSION

Society’s expectations for 24-h-7-days-per-week operations are evident in the TWU sector, where heavy workloads, long hours, irregular shifts, complicated and varying schedules, and time pressure may subject workers to inadequate rest periods, decreased sleep opportunities, and disrupted circadian cycles. These can result in worker fatigue and impaired cognitive and physical performance on the job, increasing the risks for fatigue-related worker errors, accidents, injuries, and illnesses. Further research into the incidence and characterization of fatigue, as well as into the adaptation, implementation, and evaluation of strategies for fatigue mitigation are critical for the health, safety, wellbeing, and productivity of workers in the TWU sector.

DATA AVAILABILITY STATEMENT

Data derived from public domain resources. The data that support the findings of this study are available online. See references [1–144] for Internet access to the source material.