Age is more than just a number: Implications for an aging workforce in the US transportation sector

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Applied Ergonomics 39 (2008) 542–549 www.elsevier.com/locate/apergo

Age is more than just a number: Implications for an aging workforce in the US transportation sector Stephen M. Popkin, Stephanie L. Morrow, Tara E. Di Domenico, Heidi D. Howarth Volpe National Transportation Systems Center, 55 Broadway, Kendall Square, Cambridge, MA 02142, USA Received 7 February 2008; accepted 11 February 2008

Abstract The US workforce is aging. At the same time, there are a record number of open positions in the transportation sector, which has traditionally been a well-paying, but stressful and schedule-dependent, occupation. Due to increasing longevity, need, and ability to work, a possible solution to the transportation workforce shortfall may lie within the retention and recruitment of older workers. This paper uses a socio-technical framework to examine the pertinent, though scant, literature and data related to older workforce demographics and operational needs, the regulatory environment, requisite knowledge, skills and abilities, and application of support technology and training. Although there is evidence of age-related changes in physiology and cognition, the current science remains unable to resolve how an older workforce may most appropriately be applied to transportation to maximize system safety and minimize negative impact to worker well-being. Published by Elsevier Ltd. Keywords: Aging; Transportation; Socio-technical systems

1. Introduction The United States workforce is aging. With the baby boomer generation reaching retirement age, more workers than ever before are faced with the decision of whether to leave or remain in the workforce. Older workers who remain employed past traditional retirement age, or return post-retirement, are a relatively unexplored resource that may aid in meeting labor demands of the future. However, successful utilization of this demographic necessitates tailoring for some occupations, depending on the requirements of the work. The state of the US workforce begs for a thorough examination of interactions between aging and work-related abilities. Investigating the impact of aging is particularly important within the transportation industry, as it is characterized by physically and mentally demanding tasks and long, irregular work hours. Recent changes in regulations, such as the revision of the maximum age for airline pilots to operate an Corresponding author. Tel.: +1 617 494 3532; fax: +1 617 494 3622.

E-mail address: [email protected] (S.M. Popkin). 0003-6870/$ - see front matter Published by Elsevier Ltd. doi:10.1016/j.apergo.2008.02.003

airplane from age 60 to 65 (FAA, 2007), clearly indicates that the US government is examining the future role of older workers in transportation. Whether using a cutoff of 60, 65, or something else entirely, the transportation industry is left with an age-old question: is age more than just a number? This question is examined in the current paper within a socio-technical systems framework (Moray, 2006). The socio-technical systems approach recognizes the workplace as a complex system involving interactions between people (the social system) and the tools and techniques they use (the technical system). Further, interactions between the social and technical systems are largely driven by the demands and context of the external environment. The extent to which the social and technical systems fit one another, and also meet the demands of the external environment, is a key determinant of organizational effectiveness (Pasmore, 1988). We use an adaptation of the socio-technical systems model presented by Moray (2000) to develop a better understanding of the impact older workers have on the transportation workforce (see Fig. 1). Considering the literature on aging

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middle and older age groups will outnumber younger workers as the baby boom generation reaches ages 45–64. Current trends tell us that older workers have a need and desire to continue working past traditional retirement age. Concomitantly, the extent to which this demographic is utilized by the labor force likely needs to increase to keep up with staffing requirements. However, the capacity of older workers to safely and efficiently fulfill industry demands is still to be determined. 3. Industry infrastructure: workforce needs and regulations in transportation 3.1. Workforce needs Fig. 1. Adaptation of the socio-technical systems model.

and transportation, we explore the possibility of maximizing fit and finding balance between the abilities of older workers and the design of transportation systems to ensure effective, efficient, and safe performance. 2. Societal and cultural pressures: the state of the aging workforce The 2000 Census counted 281.4 million people in the United States, a 13.2% increase over the 1990 Census population. Due in part to modern technology and medicine, people are living longer, irrespective of quality of life (Costa and Di Milia, 2008). In fact, the number of Americans aged 65 and older has been steadily increasing and is predicted to continue to grow at least through 2030. In addition, more and more older workers are choosing to remain in the labor force rather than retire. In 1994, nearly 12% of the workforce was reported to be over the age of 55 (Toossi, 2005). By 2004, this number had increased to 15.6% and is expected to continue to rise to greater than 21% by 2014 (Toossi, 2005). Societal trends, including having children later in life due to career demands and the exponentially increasing cost of education, healthcare and eldercare, are contributing to the trend of working past traditional retirement age. As the cost of living increases, people of retirement age may no longer have enough money saved to live comfortably through retirement. Not much relief is found in US-provided social security, as a typical retiree receives only 40% of their previous earnings, an average of $1,079 per month (US Social Security Administration, 2008). In addition, the rising numbers of retirees have led to concerns about the stability of the future of the social security system. According to the National Institute of Occupational Safety and Health’s Worker Health Chartbook (NIOSH, 2004), the total required labor force in 2001 was estimated at 135 million workers, and that number is projected to increase by 17 million over the next decade. The potential for a labor shortage in the near future is clear. By 2010,

Currently there are approximately four million transportation workers in the US, representing the full range of work schedules—from fixed shifts, to forward- and backward-rotating shifts (e.g., air traffic controllers), split shifts (e.g., transit), irregular and unpredictable shifts (e.g., freight railroad), and self-regulated shifts (e.g., long haul truck driving). Beyond this heterogeneity of staffing and scheduling practices to suit operational needs, there have been three large trends that have shaped the size and skill level of the transportation workforce: introduction of new technologies, greater demand, and increased competition (both within and between modes). These trends have had a differential influence on the various modes. Both the maritime and railroad industries have seen a marked reduction in staff post World War II. The railroad industry, which employed close to three million in 1946, now employs fewer than 300,000, yet transports an increasing amount of freight. This reduction in the workforce was brought on both by financial necessity and operational improvements that allowed a freight train to be run by two operating personnel rather than five. Conversely, the transit and aviation industries have bolstered staff due to heightened demand. Traditionally, transportation jobs have been highly sought after, either because of pay or freedom from the office environment. Industries like railroad and maritime were generational, where sons would often be brought into the industry by fathers. Over the years, however, the pay differential has diminished, and as such it has become increasingly difficult to recruit new transportation employees. Furthermore, the new jobs of modern society (e.g., information technology) are often perceived as requiring less personal sacrifice than transport jobs (i.e., being on call 24/7, having to be away from home for weeks or months, or being placed in dangerous or high-stress situations), and are thus more desirable despite remaining pay differences and family tradition. The confluence of the increasing availability of equally or more lucrative, less personally restrictive jobs outside of transportation and the increasing demand for transportation operators in some sectors has created the potential for a staffing gap. Add to this the transportation workforce

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aging and moving towards retirement and the potential gap becomes a very serious and immediate concern. For instance, the American Association of Railroads (AAR, 2004) estimates that 80,000 employees will have to be hired over the next 5 years just to replace those lost to retirement. Similarly, the American Trucking Association (ATA) has estimated that the heavy truck industry is currently short 20,000 drivers, and if this trend continues unabated, by 2014 the shortage will exceed 110,000 drivers (Global Insight, Inc., 2005). The Federal Aviation Administration (FAA, 2007) reports that 72% of its air traffic control (ATC) workforce will become eligible to retire over the next decade. Clearly, there is a need to replenish the transportation workforce, and the traditional pipeline is no longer sufficient to do so. 3.2. Regulations Governmental policy has the ability to support or suppress the industry’s attempt to correct its real and future staffing shortages. One simple measure would be to allow people to work later in life or entice retirees to take on a new or continuing career in transportation. In fact, the Age Discrimination in Employment Act (ADEA) of 1967 protects people over the age of 40 from employment discrimination solely on the basis of age, and as amended in 1986, covers all federal and non-federal employees in the US, with the following exceptions: (1) commercial airline pilots, (2) air traffic controllers, and (3) public safety officers. Therefore, outside of aviation, there can be no mandatory age requirement for retirement or job entry, though it is acknowledged that age discrimination is likely to be widely practiced and under-reported. With regard to aviation, according to the ‘‘Age 60 Rule,’’ passed in 1959, pilots must retire from commercial flying when they turn 60 years of age. Justification for this rule, as discussed in the Federal Register, suggests that pilots over 60 have an increased likelihood of sudden, in-flight incapacitation due to stroke or heart attack, and a ‘‘progressive deterioration of certain important physiological and psychological functions’’ (Scheduled Interstate Air Carrier Certification, 1959, p. 5247). In fact, only 1% of all commercial aviation accidents since 1930 have been due to sudden incapacitation (Li, 1994) and no supporting medical or psychological evidence on performance deterioration was provided in the docket, which appears to have been lost years ago (Woolsey, 2007). There have been two published studies (Guide and Gibson, 1991; Hilton Systems, Inc., 1994) that reported a slight increase in accident rates at advanced ages for commercial and private pilots, respectively, but both noted that the largest age risk was for pilots under the age of 40. It is unclear what is causing this heightened risk, though inexperience is likely a primary factor for the younger pilots. Given this paucity of safety risk data for older pilots, the ‘‘Fair Treatment for Experienced Pilots Act’’ was established, raising the mandatory retirement age of pilots to 65 (Wolfe, 2007).

By regulation (Air Traffic Controller Career Programs, 1972), citizens over the age of 31 are prohibited from applying for ATC positions and must retire by either the age of 56, or with rare exceptions, 61. The underlying rationale for providing a hire and retire age cutoff is twofold. First, there was the stated concern of controller burnout and loss of proficiency due to the demanding and stressful nature of the work. Second, there was the intent to provide controllers with enough time to pursue a second career if they so chose, similar in concept to military retirement. As with pilots, however, no evidence was presented in the docket demonstrating that older air traffic controllers were more likely to make errors on the job that might compromise flight safety. Two recent articles (Gokhale, 2004; Broach and Schroeder, 2005) have questioned the need for this age restriction, especially in light of the pending workforce retirement, but as yet there is no serious movement in changing ATC age requirements. Interestingly, the US Congress unwittingly voted in a de facto retirement age for the railroad industry. Passed in 2001, one provision of the ‘‘Railroad Retirement and Survivors’ Improvement Act’’ (2001) allowed rail employees to collect full retirement benefits at age 60 with 30 years of service. Previously, rail employees could not collect full benefits until age 65, regardless of years of service. This, in part, explains the recent surge in railroad employee retirements and subsequent staffing shortages. Coupled with the aviation exceptions, government policy has inadvertently limited the transportation industry from hiring and retaining an older workforce. Transportation companies typically maintain entry requirements for skill and performance proficiency. However, once passed, regardless of age, all workers are treated similarly, protected by collective bargaining agreements where applicable, and in any case by the ADEA. Additionally, few other developed countries have placed age restrictions on their transportation workforce, and where they do exist, there is little supporting data (Langford and Koppel, 2006). 4. Social system: the knowledge, skills and abilities of older transport workers Workers hired as transport operators are expected to have a number of requisite knowledge, skills, and abilities (KSAs) in order to successfully perform their jobs. In order to determine whether older workers are fit to be employed as transport operators, it is necessary to establish if age, or specific aspects of aging, impact the competencies needed to safely perform work. For the purpose of this review, we used occupational data from the Occupational Information Network (O*NET; Peterson et al., 1999) to examine jobs in the transportation sector. We compiled ratings of importance to form a master list of the most common KSAs needed for 15 jobs across transportation modes, including air, rail, highway, and maritime operations (see Table 1). A knowledge, skill, or ability was included on the master list

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Table 1 Transport operator jobs, listed by mode, used to determine common KSAs within the transportation industry Air

Rail

Maritime

Air traffic controllers

Locomotive engineers

Highway

Ship and boat Industrial truck and tractor captains operators Airline pilots, copilots, and flight Railroad conductors and yardmasters Ship, boat, and barge Heavy and tractor-trailer engineers mates truck drivers Commercial pilots Rail yard engineers, dinkey operators, Ship pilots Light or delivery service truck and hostlers drivers

Table 2 Knowledge, skills, and abilities listed in order of importance within the transportation industry Knowledge

Skills

Abilities

Transportation

Operation and control Speaking Active listening Coordination Operation monitoring Time management Critical thinking Judgment and decision making

Control precision Far vision Oral expression Oral comprehension Near vision Reaction time Selective attention Speech clarity Depth perception Problem sensitivity Spatial orientation Time sharing

Note: KSAs highlighted in bold have supporting literature.

if it was rated by job incumbents as important (scored 3 or above) for a clear majority (11 out of 15) of the selected jobs (see Table 2). Using the generated transportationrelated KSAs as a guide, we then reviewed the scientific literature regarding age effects on knowledge, skill, and ability levels. 4.1. Knowledge Knowledge of transportation (i.e., expertise) was shown to be the most important knowledge area, and the only required across all transportation modes. There are studies examining the relationship between pilot expertise and performance, but most report mixed results, and little transportation-specific research regarding this topic area exists outside of aviation. Morrow et al. (1994) found that expertise eliminated agegroup differences for pilots performing a task involving the recall of aircraft flight paths, but was not a factor for less aviation-related tasks, such as a general word recall test. The results were not replicated in their 2001 or 2003 study, though the 2003 study did suggest that older pilots with more experience also had greater recall accuracy (Morrow et al., 2001, 2003). Nevertheless, these findings highlight the importance of maintaining domain relevance when testing for expertise effects.

Other Transit and intercity bus drivers Subway and streetcar operators Taxi drivers and chauffeurs

Additionally, Salthouse and Mitchell (1990) found that work experience does not prevent age-related declines in basic cognitive processing ability, such as processing speed. However, there is evidence that pilot experience can lessen some of the age-related declines in metacognitive skills and time-sharing abilities (Tsang et al., 1995; Lassiter et al., 1996). In a review of the relevant literature, Barnes-Farrell (2005) concluded that, while flight experience does not greatly affect age-related declines in basic cognitive abilities, it does provide some benefit when performing complex, real-world tasks. She also noted that the areas of cognition that rely on expert knowledge continue to develop, or at least plateau, well into a person’s seventies. 4.2. Skills The O*Net analysis identified eight skill areas as important within the transportation industry. These included coordination, operation monitoring, time management, critical thinking, and judgment and decisionmaking. There is limited literature available regarding aging and its effect on skills specific to the transportation industry, with most focusing on the areas of judgment and decision-making. Wiggins et al. (1995) found that overall problem-solving abilities were predictive of weather-related decision-making skills for novice pilots, but not for more experienced pilots. This suggests that experienced pilots rely on more than simply general problem-solving abilities to make decisions. Llaneras et al. (1998) reported that, as a group, drivers aged 65 and older showed significant deterioration in decision-making skills when compared to drivers below age 50. However, they did not find a significant correlation between decision-making ability and age overall, indicating that chronological age alone is not a basis for determining a worker’s capability in this regard. Although we can speculate about the decision-making processes of older, more experienced workers, the existing research does little to tease apart the mechanisms underlying the relationship between age and skill. 4.3. Abilities Our analysis identified 12 abilities as important within transportation, including multiple physical and cognitive

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abilities. There is an abundance of literature available regarding aging and its effect on specific abilities, which is not surprising given the substantial physical and mental demands placed on transport operators. With regard to vision, Hitchcock (1999) found evidence that visual acuity and contrast sensitivity decline with age. Research also suggests that older pilots experience visual field loss and have a harder time recovering from glare (Hitchcock, 1999), and that older truck drivers have difficulty with depth perception (Llaneras et al., 1998). Transport operators must be able to respond quickly and effectively to signals. This is a concern with regard to older workers, as an age-related slowing in reaction time is well acknowledged in the scientific literature. A recent study compared younger (aged 20–30) and older (aged 50–60) workers’ ability to complete simple (visual discrimination) or complex (descending subtraction) tasks while employing a rapid-rotating work-rest schedule (Bonnefond et al., 2006). Age was significantly related to deteriorations in speed and accuracy on complex tasks, possibly due to high memory and attentional requirements. Similarly, Llaneras et al. (1998) found that truck drivers under age 50 had significantly faster (16–42% on average) response times across a variety of task types, as compared to drivers 65 and older. On average, cognitive processing speed slows with age, most notably after age 60 (Barnes-Farrell, 2005; Hardy and Parasuraman, 1997). This has implications for timedependent problem-solving tasks and environmental monitoring tasks, both common within the transportation industry. Additionally, it is promising that although fluid cognitive abilities (e.g., abstract reasoning) are more affected by age than are any other cognitive functions, they seem to be responsive to educational interventions, even those performed later in life (Barnes-Farrell, 2005). Llaneras et al.’s (1998) study on truck drivers also found that older drivers performed significantly worse than younger drivers on selective attention tasks. Selective attention is the ability to concentrate on a task without distraction (Peterson et al., 1999), and is thought to be facilitated by inhibition (Hardy and Parasuraman, 1997). Inhibition may deteriorate due to normal, age-related declines in frontal cortex functioning (Dempster, 1992; Rafal and Henik, 1994), and can result in the inclusion of irrelevant information into working memory. Other theories of aging suggest an overall decline in central processing speed and a reduction in working memory capacity, both of which inevitably affect performance on complex tasks (Broach and Schroeder, 2005). Although experience has been shown to lessen some of these effects (Schroeder et al., 1999; Tsang et al., 1995; Tsang and Voss, 1996; Tsang and Shaner, 1998; Lassiter et al., 1996), more research is necessary to investigate the trade-offs between losses in abilities and gains in experience. Field research in transportation is particularly essential, as workers operate in dynamic environments that are difficult to replicate in the laboratory, especially in the face of unusual, timeconstrained, or emergency situations.

5. Technical system: age implications for job design The projected expansion of the 55-plus labor force by close to 100% from 1994 to 2014 (Toossi, 2005) provides an opportunity for the transportation industry to fill openings, but is not without challenges. Older workers are apt to face chronic health problems that can affect their ability to work safely and effectively. For example, stress and musculoskeletal disorders are reported more frequently by older than younger workers (Jones et al., 1998) and are a significant factor in ill-health early retirements. Moreover, the prescription drugs used to treat these health issues may have side effects that further impact aspects of work, such as a person’s recovery from daily activities during sleep. Since the quantity and quality of sleep already degrades as part of the aging process, such interactions are potentially problematic. As mentioned previously, research has demonstrated that various human abilities (e.g., psychomotor, cognitive, perceptual) deteriorate as people get older (e.g., Llaneras et al., 1998). Even in cases where work demands remain constant over time, these decrements may result in greater employee health and safety concerns if there is not compensation through increased work support or control over work (Cox and Griffiths, 1995). Retaining existing older workers and/or the successful recruitment of older people back into the workforce for second careers is consequently a complex undertaking. Griffiths (1999) recommends taking advantage of the strengths of older, more tenured workers in terms of their experience and greater knowledge base, but cautions not to disadvantage them in terms of relative weaknesses in decreased physical and certain cognitive abilities. Additionally, she notes that designing and managing work in ways that promote health and job satisfaction is vital. Finally, consideration should be given to the possibility that the nature of work may change with seniority (as confounded with age; Griffiths, 1999) and that older and younger workers do not think about their work in the same way. For example, Warr (1998) suggested certain aspects of work may be valued more or less as people age: feedback, externally generated goals, and variety become less important, while job security is increasingly significant. Additionally, Huuhtanen and Piispa (1992) note that volume of work, time pressures, and flexible work hours are important issues to evaluate and consider tailoring. 5.1. Training Organizations tend to place high value on outcomes such as job performance and safety. Research findings regarding the relationship between aging and performance are mixed, and often appear to be dependent on how performance is measured (ratings or objective productivity measures) and analyzed (control for tenure and/or satisfaction, and differences in performance may wash out). In fact, McEvoy and Cascio (1989) and Waldman and Avolio (1986) found

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little consistent evidence for an age–job performance relationship in the meta-analyses they conducted. Results of a more recent meta-analysis (Kubeck et al., 1996) agree with much of the aging literature that notes cognitive decrements, but conflict with the adult education and training literature which posits that adults can learn and benefit from education and training at all points in life. Generally, Kubeck et al. (1996) found that older adults take longer to cover training material and have less mastery of materials at the end of training than those who are younger. Findings evidencing greater differences between older and younger adults also indicate greater individual differences among older adults on various outcome measures. Although they did not typically benefit as much as younger adults, some older adults improved at least as much, or more with training, suggesting that training mastery should not be ignored by employers. Armstrong-Stassen and Templer (2005) identified three key issues with regard to training older workers. First, there must be access to training, which was shown to be limited or nonexistent for older employees in a literature review by O’Reilly and Caro (1995). Specifically, training must not only be accessible, but older employees must also be encouraged to partake in it. Second, training must be adapted to be appropriate to older workers, as they have different needs, different learning styles and different experience levels than younger workers (Allen and Hart, 1998; Griffiths, 1997). Examples of appropriately tailored training include putting emphasis on ‘‘hands-on’’ learning over lecture formats, accommodating for different learning styles by making the learning self-paced, and allowing for adequate time to learn. A study investigating learning after safety training found that both older (over age 45) and younger workers performed better when the computer-based training they received included text, pictures, and audio narration (in contrast with lesser combinations; Wallen and Mulloy, 2006). Finally, it is important to provide training to managers, so that they understand age awareness and the effective utilization of older employees (Griffiths, 1997). In 2000, the American Association of Retired Persons reported that only 25% of a sample of 400 US organizations indicated that they educate managers regarding ways to effectively utilize older workers. 5.2. Job design Research suggests that ergonomic design of the work environment and tools is likely to benefit employees of all ages, but in particular may be useful in maintaining the capacities and capabilities of workers as they age (Welford, 1988; Waldman and Avolio, 1986). Generally, tool design has been found to impact the amount of work accomplished and energy expended during work (Grandjean, 1988); for example, handle shape and size affect exerted forces (Cochran and Riley, 1986). However, it stands to

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reason that improved work performance may only be realized when tools are properly utilized (Rockwell and Marras, 1986). In a study where performance was evaluated (Schwoerer and May, 1996), older workers benefited more from ergonomic tool design than did younger workers. In addition, when using less effectively designed tools, older workers performed only slightly worse than younger, suggesting that they were able to compensate with skills and experience. Finally, Llaneras et al. (1998) found that compensatory and training-oriented interventions were effective as a means of limiting degradation of driving abilities: prescriptive and clear direction in the form of auditory commands as part of invehicle navigational aids appeared to bolster perception, cognition, and psychomotor abilities through a reduction in navigational errors and driver workload. Another aspect of job design includes work-scheduling considerations. Both flexible work hours (Huuhtanen and Piispa, 1992) and part-time work arrangements (AARP, 2000) have been reported as important and effective approaches for managers to consider implementing as a way to more effectively utilize older employees. Indeed, the transportation industry may be a candidate for such measures, as mobility needs typically extend beyond a traditional day shift. Employees are often required to work nontraditional hours, thus performing safety-critical jobs at night when the body’s circadian clock promotes sleep, and resulting in off duty time during the day when sleep is inhibited (Lavie, 1986). Not surprisingly, research findings have evidenced that workers on otherthan-day shifts or on rotating schedules (RadosevicVidacek et al., 1995) tend to suffer from reductions in main sleep spanning 1–3 h (A˚kerstedt, 1991). Moreover, night shift work in particular is associated with poor sleep quality in comparison to working morning or afternoon shifts (Tepas et al., 1985; Torsvall et al., 1989). In combination with the effects of aging on sleep, increased health problems and the resulting need for prescription drugs, it may be suggested that it is not ideal for older workers to perform shiftwork, especially on nontraditional shifts. Barring obvious equal employment opportunity issues, scheduling to avoid such arrangements may appear to be a reasonable workaround, until one considers that assigning shifts in transportation is often per union agreement and accomplished using a seniority-based bid system. The outcome of such systems is that the most tenured and experienced workers often bid into fixed, day shifts, while the lesser experienced and tenured are forced into nontraditional and irregular shift schedules. Historically, more senior employees also tended to be older; however, to the extent that today’s workers engage in multiple careers, it is increasingly likely that older employees are no longer the most senior. In these cases, it is particularly concerning to realize that older shiftworkers who are not experienced are probably the worst candidates for nontraditional shifts, yet the most likely to end up working them.

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6. Conclusions: the future for older workers in transportation As a result of complex interactions between lifestyle choices, socioeconomic variables and financial needs, people are working later into life; age 65 is no longer considered the cut-off age for retiring, except in a few rare cases written into US law. Simultaneously, the transportation sector, which has historically relied on staffing positions through traditional sources, such as ‘‘father and son’’ in the case of railroad and maritime work, and military retirement in the case of pilots, is finding these traditional personnel pipelines breaking down, making it difficult to fill open positions. As a result, these companies have become understaffed, and must rely more heavily on those remaining, either through long working hours or additional shifts, to meet operational demands. Because transportation is a 24/7 endeavor, the stress placed upon employees by working shifts must be considered relative to other changes that occur within people as they age. Employees may be able to compensate for certain decrements in sensation, perception and cognitive functioning through experience, training, and technology. However, far less is known about aging as associated with circadian rhythm frailty, difficulty obtaining appropriate levels of restorative sleep, and the general increased use—and therefore interaction effect—of prescription and over-the-counter medications. On one hand there appears to be a growing older workforce that can be tapped to offset the shortage of transportation workers. Still, much care needs to be taken in how, when, and how often this potential workforce is applied. Managers would be shortsighted to consider the newly hired 25-year-old bus operator and the new 65-year-old operator as equivalent with respect to scheduling and staffing. Each has potential advantages; quick reaction time in the case of the younger driver, and more experience likely leading to better judgment in the older driver. However, there are also concerns to be addressed: younger drivers may be more impulsive or aggressive, while older operators are likely to struggle with degradations in vision, hearing and cognitive processing speed. Indeed, training and technology aids may help improve the safety of both groups, but will realistically only provide a partial solution. The implications of this review are two-fold. First is that the management of technological systems must consider workforce age along with other, perhaps more typical demographic parameters, such as gender, culture and mother tongue. Also, training and tailored job and tool design may enhance the ability of a workforce to perform their jobs safely and effectively, if what is known about human physiology, cognitive functioning, and other parameters over the lifespan is taken into account. The second implication follows from the first: additional data collection and investigation is needed to fill research gaps and provide a basis for future age-related decision-making. Much of the available literature concerning older shift-

workers operationalizes ‘‘older’’ as workers within an age range of 40–55 years, but as previously noted, workforce trends indicate that workforce participation by those 65 years and older will only increase. We frankly know very little about this group, short of extrapolation, that can inform policy, human resource managers, trainers, work schedulers, or ergonomists. Only by conducting additional longitudinal research and development will it be possible to definitively answer the age-old question: is age more than just a number? Acknowledgments The views of the authors do not purport to reflect the position of the Research and Innovative Technology Administration, the US Department of Transportation or the US Government. References AARP, 2000. American Business and Older Employees: A Summary of Findings. American Association of Retired Persons, Washington, DC. Air Traffic Controller Career Programs. Public Law 92–297, May 17, 1972, 86 Stat., pp. 141–145. A˚kerstedt, T., 1991. Shift work and sleep disturbances. In: Penzel, T., Podszus, T., von Wichert, P. (Eds.), Sleep and Health Risk. Springer, Berlin, pp. 265–278. Allen, J.M., Hart, M., 1998. Training older workers: implications for HRD/HPT professionals. Perform. Improve. Quart. 11, 91–102. American Association of Railroads, April 28, 2004. Washington Press Release: Railroads Expect to Hire More than 80,000 New Workers Over the Next Six Years. Armstrong-Stassen, M., Templer, A., 2005. Adapting training for older employees: the Canadian response to an aging workforce. J. Manage. Develop. 24, 57–67. Barnes-Farrell, J.L., 2005. Older workers. In: Barling, J., Kelloway, E.K., Frone, M.R. (Eds.), Handbook of Work Stress. Sage Publications, Inc., Thousand Oaks, CA, pp. 431–454. Bonnefond, A., Harma, M., Hakola, T., Sallinen, M., Kandolin, I., Virkkala, J., 2006. Interaction of age with shift-related sleepwakefulness, sleepiness, performance, and social life. Exp. Aging Res. 32, 185–208. Broach, D., Schroeder, D., 2005. Review of the Scientific Basis for the Mandatory Separation of an Air Traffic Control Specialist at Age 65 (DOT/FAA/AM-05/6). Civil Aerospace Medical Institute, Oklahoma City, OK. Cochran, D.J., Riley, M.W., 1986. The effects of handle shape and size on exerted forces. Human Factors 28, 253–265. Costa, G., Di Milia, L., 2008. Ageing and shiftwork: a complex problem to face. Chronobiol. Int. (in press). Cox, T., Griffiths, A., 1995. The nature and measurement of work stress: theory and practice. In: Wilson, J.R., Corlett, E.N. (Eds.), Evaluation of human work: a practical ergonomics methodology. 2nd ed. Taylor & Francis, Philadelphia, PA, pp. 783–803. Dempster, F.N., 1992. The rise and fall of the inhibitory mechanism: toward a unified theory of cognitive development and aging. Develop. Rev. 12, 45–75. Federal Aviation Administration, December 14, 2007. Washington Headquarters Press Release: FAA Statement on Pilot Retirement Age. Global Insight, Inc., 2005. The US Truck Driver Shortage: Analysis and Forecasts. American Trucking Association. Gokhale, J., 2004. Mandatory Retirement Age Rules: Is It Time to Re-evaluate? United States Senate, Special Committee on Aging, Washington, DC.

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