Personal Vehicle Transportation

Joachim Meyer

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

National Research Council (US) Steering Committee for the Workshop on Technology for Adaptive Aging; Pew RW, Van Hemel SB, editors. Technology for Adaptive Aging. Washington (DC): National Academies Press (US); 2004.

Technology for Adaptive Aging.

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10Personal Vehicle Transportation

Joachim Meyer.

The face of aging is rapidly changing. Although older age in the past was mainly considered as a transient period in which abilities and activities decline, today more and more older people hope to spend their later years filled with activity and meaningful and enjoyable involvement. A crucial precondition for well-being in older age is independence. A condition for this, in turn, is the ability to move easily from place to place, i.e., the ready availability of means of transportation. Older people in urban settings may have access to various forms of public transportation. Some of these are particularly adapted to the needs of older travelers (e.g., “kneeling” buses that facilitate entrance and exit, paratransportation services that pick up people at their homes). Many mass-transit systems in metropolitan areas are also designed to accommodate older passengers. These forms of transportation have obvious societal and environmental value, and their use should be encouraged. However, transportation for the majority of older adults in the United States, and increasingly in other parts of the world, means using a privately owned and driven car (Coughlin, 2001a). The issue of well-adjusted aging is therefore closely related to the ability to continue to drive for as long as possible and to maintain the independence provided by a car. However, an older person's driving at an advanced age may cause concern if the person has some limitations that affect driving safety.

Numerous questions need to be answered regarding older drivers' continuing to drive. Government and regulatory agencies, car manufacturers, healthcare providers, families, and society at large must address these questions. The answers to these questions and the solutions provided by the different agencies should be based on sound scientific research rather than on guesswork and unfounded beliefs. Some of the relevant data are already available from the large body of research on aging and driving, but many questions remain open. These issues should be at the focus of the research agenda for the coming years.

In this chapter I address a number of relevant issues. I begin by discussing the transportation needs and driving patterns of older drivers. I review some of the reasons why older drivers might differ from other driver populations and focus on vision as one of the fields in which there is compelling evidence for age related decline in abilities that can affect driving. I then discuss whether older drivers constitute a safety risk (and for whom) and under which conditions they do so. I then review some of the changes that older drivers make to cope with the potential safety problems. I then discuss technologies and new in-vehicle devices and their potential to help older drivers, as well as some of the possible problems that may be associated with these technologies. I end the chapter with a brief discussion of some of the necessary research directions on older drivers in view of the new technologies that are available.

CONTINUED DRIVING AT AN ADVANCED AGE

The wish to be able to drive for as long as possible is understandable, given the fact that especially in rural and suburban communities there is often no alternative form of transportation other than a car. A person must use a car to go shopping, to access medical services, to attend social functions, and to visit friends and family (Rosenbloom, 1993). The loss of a driver's license thus implies losses in many aspects of life, including personal freedom, independence, and the possibility of making useful contributions to society (Waller, 1991; Coughlin, 2001b). For the importance of mobility for the well-being of older people, see also Carp (1988).

Indeed, an increasing number of people continue to drive up to an advanced age, leading to a steady growth in the number of “older old” drivers, those aged 75+ or 80+ according to different definitions (Barr, 1991). Kosnick et al. (1988) report that people 65 years and older use the automobile for 80 percent of their errands and trips. Similarly, Jette and Branch (1992) found that older drivers continue to drive for as long as possible and they resist any change in the preferred mode of travel, although they may lower the frequency of travels. Chipman, Payne, and McDonough (1998) report that 37.5 percent of a sample of Ontario, Canada, drivers aged 80 and over reported that they still drove. Relatively healthy older people were especially likely to drive. Although most of the drivers and the nondrivers suffered from two and more chronic diseases and more than 84 percent of both groups suffered from at least one chronic disease, the drivers had fewer chronic diseases than the nondrivers.

Given the importance of driving, driving cessation can have strong adverse effects on a person. For example, Marottoli et al. (1997) showed an increase in depressive symptoms among older adults who stopped driving. The continuing ability to drive seems to be a precondition for some older people's well-being. However, this is not a general need. Chipman et al. (1998) found in their study of 80+ years old drivers in Canada that driving cessation did not lead to a significant decrease in contacts with relatives and friends. Thus, driving, at least for this group, was not necessary for maintaining social relations.

WHAT MAKES OLDER DRIVERS DIFFERENT?

Discussing the issue of older drivers assumes that this group differs in some way from other groups of drivers. Obviously, one variable on which older drivers differ from other drivers is their age. However, it is not at all clear at what age a person becomes an “older driver.” Visual capabilities begin to decline in the 20th year, whereas other skills and abilities remain often practically unimpaired up to an advanced age. There is no general age criterion to define older drivers, and different studies have adopted different definitions.

In spite of the lack of a universal criterion for defining older drivers, a fairly large number of studies show systematic differences between drivers as a function of age. The cause for these differences is not always clear. Below I discuss four possible reasons for differences between age groups.

Cohort Effects

Drivers from different age groups belong to different generations. These generations grew up in different cultural, social, and technological environments. Consequently the differences between members of the age groups may be due to these generational effects, which caused them to be exposed to different environments during critical phases of their development. One cohort effect that affects driving is the progressive motorization of Europe and the United States. Whereas most 20-year-old people today have access to cars, the same was not true 60 years ago. Women in particular had less driving experience. These differences can still affect older women's current driving behavior. If this is the case, then differences between today's older men and women in the frequency of trips and the use of cars will disappear in the future when the baby boom generation approaches retirement. Also, overall car use and trip frequency of older drivers will increase for the older drivers of the future. This will lead to an even greater increase in the presence of older drivers on the road, beyond the increase due to changes in demographics.

Changing Lifestyles

The aging process is not only a physiological process in which biological systems undergo changes, but it is also a social process in which a person changes involvement in activities and obligations. One major change that affects the driving habits of many older drivers is the fact that older people cease to commute regularly after they retire from work. This relieves them of the need to drive daily without considering the traffic and weather conditions. After retirement, these drivers are likely to limit their driving in adverse conditions, and after some time they may feel less confident driving at all in these conditions. Thus the exit from the work force (or other changes in lifestyle) may be a cause for changes in driving patterns. Here, too, future older drivers will differ from today's older drivers because of the expected continuing involvement of older people in the work force beyond the current retirement age.

Disease and Medication

The aging process is related to an increase in the frequency of chronic and acute diseases that have adverse effects on a person's functioning in general and driving in particular. The most extreme cases are degenerative diseases, such as Alzheimer's disease, that limit a person's ability to function to an extent that eventually requires constant supervision and care. More frequent are other diseases with less severe impacts. It is not quite clear how chronic disease affects driving ability. For example, Gresset and Meyer (1994) found in a study on Canadian drivers that only arrhythmia (from among a number of medical problems) was associated with a significant increase in the risk of being involved in a crash. In addition to the possible adverse effects of the diseases themselves, there are also possible adverse effects of medication that is taken to control chronic or acute health problems. Some types of medication may impair driving ability to an extent that makes continued driving unsafe.

Age-Related Changes

The fourth possible cause for differences between age groups is changes that are due to the physiological aging process itself. With increasing age certain basic functions change, and in most cases these changes are in the direction of lessened abilities. An extensive review of age-related sensory, cognitive, and motor changes is presented in Chapters 2 and 3 of this report (Schaie, and Ketcham and Stelmach, this volume). I concentrate in the following sections on those changes most likely (or actually demonstrated) to affect driving. With respect to driving, Planek (1972), in one of the earliest larger reviews of the literature on older drivers, identified three interconnected areas of deficiencies: (1) sensory reception, (2) neural processing and transmission, and (3) motor response. Later studies put greater emphasis on cognitive aspects of driving that are related to decision making (Hakamies-Blomqvist, 1996). Llaneras, Swezey, Brock, and Rogers (1993) and Shaheen and Niemeier (2001) summarize some of the age related sensory and cognitive changes that affect driving.

SOME AGE-RELATED CHANGES THAT AFFECT DRIVING

Vision

One domain in which there is compelling evidence for age-related changes is vision. This sensory ability is particularly important, because driving is a continuous control task that is largely guided by visual information. Malfetti and Winter (1986) suggest that 85-95 percent of the sensory cues in the driving task are visual. It is therefore reasonable to assume that changes in visual performance are likely to affect driving.

The decrease in visual abilities begins after the age of 20 and continues throughout a person's life. Shinar and Schieber (1991) reach a number of general conclusions regarding the effect of normal aging on visual perception. First, apparently all visual functions deteriorate with age. Second, the amount, rate, and onset of deterioration vary widely between individuals and functions. Third, whereas static acuity begins to deteriorate in the 60s, other visual abilities deteriorate earlier. Fourth, performance differences between individuals increase with age. Table 10-1 presents a list of some of the major visual abilities that are relevant for driving. It also lists changes that occur with age in each of these abilities and the impact that these changes are likely to have on driving.

TABLE 10-1

Age-Related Changes in Visual Abilities.

The importance of vision for driving and the relative ease of administering vision tests led to the almost universal screening of drivers according to their visual ability. Tests of visual acuity are standard in the licensing procedure of most countries, and many countries require periodic retesting of acuity after a certain age. However, a closer inspection of the aging-related changes in visual performance shows that the changes in static acuity (which is measured in most vision evaluations) are by no means the only changes that occur. Also, it appears that static acuity may not be the visual ability that is most relevant for safe driving. Groeger (1999) points out that, in spite of the long history of research on vision and driving, very little is known about the role of different visual parameters in driving.

This fact that it is not at all clear what visual abilities are actually crucial for safe driving points to one of the major issues that require research and clarification in the future. Driving ability is likely to depend on factors that are difficult to measure. Also, drivers can be highly adaptive and can compensate for deficiencies in certain areas by changing their behavior (use different driving techniques, change the conditions in which they drive, use technology to help them deal with some of the problems, etc.). It will therefore be difficult to come up with a valid, objective test that can predict who can and who cannot continue to drive safely. Clearly, simply measuring visual acuity is not enough.

The age-related changes in vision presented in Table 10-1 are by no means isolated phenomena. Rather, many of these changes are connected and may affect driving performance in similar conditions. One condition in which many of the changes will lower the older driver's ability to obtain the necessary visual information for driving is at dusk and dawn and in darkness. Here a decrease in contrast sensitivity, general diminished night vision, and prolonged recovery from glare make driving more difficult and stressful. Older adults' vision in low illumination is impaired, relative to younger adults, even if they are in good eye health (Owsley and Sloane, 1987; Sloane, Owlsey, and Alvarez, 1988). The decrease in contrast sensitivity in older adults can be attributed to age-related reduction in pupil size and the loss of lens transparency (Owsley, Sekuler, and Siemsen, 1983; Sloane et al., 1988). The effects of aging and decreased retinal illumination (for example, because of tinted glass) are not additive. It seems that aging enhances the effects of limited illumination. Levels of transmittance of tinted glass that have no effect on younger drivers can impair vision for older drivers (LaMotte, Ridder, Yeung, and DeLanel, 2000). Thus when any manipulation or condition can lower the retinal illumination, special attention should be given to the evaluation of its effect on older drivers.

Changes in vision are obviously not the only age-related changes. In addition to the aging-related changes in visual abilities, a number of other major changes in sensory, motor, and cognitive functions are likely to occur with age. I briefly review the other major changes and point out their potential relevance for driving.

Hearing

Hearing acuity decreases progressively, beginning as early as age 40 (e.g., Stelmachowicz, Beauchaine, Kalberer, and Jesteadt, 1989). The main changes are in the higher frequency range. The causes for these changes can be structural changes with aging, the cumulative effects of noise exposure, the result of traumatic events or disease, or side effects of certain types of medication. The hearing loss itself does not necessarily have direct implications on driving performance. However, it needs to be considered when auditory stimuli are intended to guide the driver or to provide warning information. The design of these auditory displays may have to take the changing hearing abilities of older drivers into account.

Attention

The effects of aging on attention are complex. There exists a distinction between different attention skills. One is focused attention, which is the ability to concentrate resources on a single task or information source without being distracted by other sources of information or cognitive processes. A second skill is divided attention—the ability to divide attention between a number of concurrent tasks and the monitoring of different concurrent stimuli. A third skill is attention control, which is a person's ability to switch the allocation of attentional resources from one task to another. There is evidence that older adults have greater difficulties dividing attention effectively compared with middle-aged and younger adults (Brouwer, Waterink, van Wolfelaar, and Rothengatter, 1991). The problem is particularly pronounced when two tasks require the same output modality (e.g., motor responses) and is reduced when the tasks employ different modalities (Brouwer, Ickenroth, Ponds, and van Wolfelaar, 1990). In a study on selective attention, Mihal and Barrett (1976; see also Barrett, Mihal, Panek, Stern, and Alexander, 1977) found a correlation between selective attention and accident rates for drivers 45-64 years old, and they found no such correlation for drivers 25-43 years old.

Memory

The existence of aging-related changes in memory is well established (e.g., Jacoby and Hay, 1998). Problems with short-term memory may cause difficulties in retaining information over short periods of time (e.g., instructions on route choice). Problems with long-term memory may be in the encoding of information (people may find it difficult to learn new names, routes, or information). Other problems with long-term memory may be in the retrieval of information, where information that was encoded in the past (which is evident by the fact that at some time in the past a person remembered this information) is now temporarily unavailable. Although these problems can occur at any age, they become increasingly common when a person ages. The memory difficulties may affect the use of new in-vehicle technologies, for example, by making it more difficult to remember procedures for using the system or by interfering with the recall of names and codes that are used in speech-activated systems.

Another domain where aging-related changes may impact performance is skill acquisition (Craik and Jacoby, 1996). Generally skill acquisition becomes slower with age, and a person will find it difficult to alter familiar ways of performing certain tasks. On the other hand, the procedural memory for familiar tasks and skills may remain intact up to a very advanced age. Thus a person can perform complex sets of actions, such as playing a musical instrument or driving a car. However, they may find it difficult to acquire some new skills that require changes in well-established routines.

Information Processing

The major change in information processing is a general slowing in processing speed. This causes a lengthening of response times and slower actions and, in particular, slower responses to unexpected events (e.g., Falduto and Baron, 1986). One study that dealt with simple and choice response times as a function of age showed that simple response times were relatively little affected by age, whereas choice response times were much more severely affected (Fozard, Vercruyssen, Reynolds, Hancock, and Quilter, 1994). With respect to driving, it appears that there are only small differences in response times to hazards on the road as a function of age. It seems that older drivers are able to brake rapidly when they encounter a problematic situation as long as they expect it (Korteling, 1990; Lerner, 1993; Olson and Sivak, 1986).

Decision Making

Some age-related differences in decision making have been identified (see Schaie, this volume), but decision processes that are relevant for driving seem to be relatively little affected by age. For instance, a study by Dror, Katona, and Mungur (1998) showed no effect of age on the speed of risk-taking decisions. However, one difference that seems to exist is that with increasing age people become more safety conscious (Boyle, Dienstfrey, and Sothorn, 1998). This may be due to the fact that the consequences of adverse events, such as traffic accidents or falls, are likely to be more severe for older people than for younger ones.

Actions and Motor Behavior

In addition to the cognitive changes that occur with age, there are also motor changes. Together with the cognitive slowing of responses, there often occurs a motor slowing of responses, which causes an older person to perform a movement more slowly than a younger person. Under certain conditions this may delay responses to safety hazards.

Muscular strength decreases approximately 12-15 percent between the ages of 30 and 70 (Blocker, 1992). Overall there is clear evidence for a loss of strength with age, especially after the age of 65. This loss of strength is more pronounced in women than in men (Bassey and Harries, 1993). There is also a loss in the speed of muscle contractions and coordination with age (Blocker, 1992). Thus an older driver is likely to have less strength than a younger person and may consequently have more need of power steering or power brakes.

A third characteristic related to aging is lowered flexibility. Approximately half of the population over age 75 experiences some degree of arthritis (Adams and Collins, 1987). This makes vehicle ingress and egress more difficult. It also limits a person's ability to turn the head and trunk, causing difficulty looking toward the sides and rear of the car. In particular the flexibility of the neck diminishes with age, leading older drivers to have less flexion and extension and rotation capability in the neck compared to younger people (Kuhlman, 1993). This lowered motility of the neck and head is a likely cause for accidents in which an older driver either collides with an object that is behind the car when backing up or fails, when changing lanes, to see a vehicle that comes up from behind in a parallel lane.

ARE OLDER DRIVERS A PROBLEM AND, IF SO, WHAT IS THE PROBLEM?

The age-related changes listed above seem to indicate that older drivers are likely to constitute a traffic safety problem. However, contrary to common beliefs, it is not at all clear whether older drivers are indeed a safety risk. There are some undisputable facts. For one, the fatality rate of older drivers is high compared with other age groups. It is close to the rate of 16-24-year-old drivers. Thus older drivers are at a greater risk of dying in an accident than most younger drivers.

There are two possible causes for the increased fatality rate. First, older drivers may be more likely to die in accidents because of their frailty and fragility. Impact forces that are negligible for a younger person can lead to severe and even fatal injuries for an older person (e.g., Evans, 2000). Therefore the increased fatality rate is not an indication that older drivers constitute a safety risk unless we consider their exposure to risks to themselves as a problem.

The second possible reason for the increased fatality rate of older drivers is that they are more likely to have an accident than younger drivers. There is some evidence that there is an increase in accident involvement for older drivers, but the strength of this evidence is not clear. It is also unclear at what age this increase occurs. Different studies point to different ages. For example, in a Florida accident database Abdel-Aty, Chen, and Schott (1998) found that drivers over age 64 (as well as drivers under 25) were more likely to be involved in crashes. In contrast, Kweon and Kockelman (2003) analyzed crash involvement and severity for different age groups, controlling for vehicle type, accident type, and driver exposure. They found that overall crash involvement was lower for 60+ year old drivers or equal to that for middle-aged drivers. Male older drivers had 4.74 crashes per million miles, whereas male middle-aged drivers had 6 crashes per million miles. For female drivers the corresponding numbers of crashes were 5.52 for the older drivers and 5.59 for middle-aged drivers. These numbers were much lower than the crash rates for drivers up to the age of 20, which were 21.79 for males and 20.24 for females.

Li, Braver, and Chen (2003) attempted to determine the relative importance of older drivers' fragility and their increased crash involvement for the increase in the fatality rates for older drivers. Their analysis showed an increase in the rate of deaths for 1,000 drivers involved in crashes, beginning with age 60. The increase continued with advanced age, and at age 80 or older the chances of dying when involved in a crash were 4.3 times higher for males and 5.2 times higher for females than the chances for 30-59-year-old drivers. Crash involvement (as indicated by the number of crashes per vehicle miles traveled) also increased with age. However, this increase began later and was smaller. The accident involvement for the 70-74-year-old group of drivers was still very close to the accident involvement rates for middle aged drivers. In the 75-79-year-old drivers the accident rate was 1.7 times the rate for middle aged drivers. A noticeable increase is evident for the 80+ year-old drivers. They had 3 times (for males) or 2.6 times (for females) the crash involvement of middle aged drivers. These rates were still smaller than the rates for 16-19-year-old drivers, who had accident rates that were 4 times the rates for middle aged drivers.

Older drivers have an increased chance of being involved in certain types of accidents. They are overrepresented in collisions in intersections where they are usually hit when entering the intersection without giving the right of way (Hakamies-Blomqvist, 1993). A disproportionately large number of accidents occur when driving across traffic (as in left turns in countries where people drive on the right side of the road). Evans (1991) mentions that older drivers are also particularly likely to be involved in accidents during backing and parking maneuvers, which are probably caused by older drivers' limited flexibility and ability to turn and their limited peripheral fields of view. When involved in an accident, older drivers are more likely to be considered the party at fault and legally responsible (Cooper, 1990; Hakamies-Blomqvist, 1994).

One reason why it is so difficult to answer the question whether older drivers constitute a safety risk is the great variety of ways in which one can compare the data for different age groups. Each comparison has certain advantages and disadvantages (see Hakamies-Blomqvist, 1998, for an in-depth discussion of the issue). Computing crash rates by adjusting to the number of licensed drivers (as was, for example, done by Evans, 2000) will lead to an underestimation of crash rates for older drivers because a fairly large number of older drivers maintain a driver's license but have in fact stopped driving. Other ways to compare data have different problems. For example, computations of the number of crashes per 1 million miles driven for different age groups (as well as other measures of crash involvement) have to be based on the number of crashes in some database. A crash is more likely to be reported if it leads to severe injury or a fatality. Given that older drivers are more vulnerable, crashes in which they are involved should have a greater chance to be reported in an accident database. Consequently the crash rate for older drivers will seem to be high.

The issue is further complicated by the fact that the older driver population is highly diverse. Even if the crash rate for older drivers is indeed higher than for younger drivers, it is not clear what drivers cause this increase. With age, a growing percentage of people suffer from severe debilitating diseases, the most frequent being Alzheimer's disease (Evans, 1990). It has been shown that Alzheimer's disease leads to an increase in accident risks (e.g., Drachman and Swearer, 1993; Dubinsky, Williamson, Gray, and Glatt, 1993; Hunt, Morris, Edwards, and Wilson, 1993). Part of the increase in accident rates for older drivers could be due to greatly increased accident risk for a fairly small group of older drivers who suffer from dementia or severe sensory problems (of which they may not be aware). Unimpaired older drivers may not constitute a risk.

DRIVING CHARACTERISTICS OF OLDER DRIVERS

Older drivers are obviously aware of the fact that they are aging and that some of their sensory, cognitive, and motor abilities change. They tend to respond to these changes by driving differently from when they were younger. They mainly tend to limit their driving to conditions with which they feel comfortable. The selective limitation of driving in adverse conditions is essentially a process of self-regulation. This adaptive response is highly appropriate (Eberhard, 1996). As early as 1968, a study showed that older drivers are less likely as a group to drive at night or in heavy traffic (Planek, Condon, and Fowler, 1968). More recently Ball and colleagues (1998) studied a sample of drivers in seven age categories from 55 up (mean age 70) and three categories of accident involvement (none, 1-3, and 4 and more). More than 80 percent of the sample reported often or always avoiding driving at night, about 70 percent avoided driving during rush hour, and almost 70 percent avoided driving on high-speed interstates. About 30 percent avoided driving in high-traffic roads. About 20 percent reported avoiding driving alone and turning left across traffic. Less than 20 percent often or always avoided driving in rain. Older drivers who were more visually or cognitively impaired reported more avoidance and fewer driving days. There were small correlations between crash involvement in the past 5 years and avoidance of driving during rain, driving in rush hour, and left turns.

Another adaptive response that is evident in various studies is that older drivers tend to drive more slowly than younger drivers (Boyle et al., 1998; Hakamies-Blomqvist, 1994; Planek, 1981). This is true even when they are involved in an accident (Hakamies-Blomqvist, 1993). Thus it is reasonable to conclude that the driving style of older drivers differs to some extent from that of younger drivers (Cooper, 1990; Rothe, 1990).

Older drivers are aware that they drive differently, and they tend to consider themselves as a group to be cautious, courteous, and safe drivers compared with younger drivers (Nelson, Evelyn, and Taylor, 1993). The impression that older drivers tend to be more cautious is supported by research. Shinar, Schechtman, and Compton (2001) analyzed self-reports of driving behavior in the U.S. driving population. They showed that women report observing speed limits more than men and that older drivers (over age 50) report observing speed limits more (48 percent) than 26-50-year-old drivers (42 percent) or drivers under the age of 26 (34 percent). Older male drivers reported more use of seat belts all the time than younger drivers (79, 66, and 54 percent for the three groups, respectively). There was no such effect for female drivers, among whom 78 percent overall reported using the seat belt all the time. The increased use of seat belts by older drivers supports the notion that caution increases with age and is not a cohort effect. Most older drivers began driving when seat belt use was rare, and they adopted it relatively late in life. Younger drivers, in contrast, were generally exposed to the message to “buckle up” from the time they began to drive.

The self-regulation of older drivers affects their accident patterns. They were found to be comparatively less involved in accidents at night, during bad weather, or in bad road surface conditions than younger drivers, and they were less likely to be in a hurry, to be intoxicated, or to be distracted by nondriving activities (Hakamies-Blomqvist, 1994).

The self-regulation that older drivers apply to their own driving is probably the main reason for the relatively small increase in crash risk with age in spite of the numerous age-related changes that should have an adverse effect on traffic safety. Older drivers actively lower their exposure to problematic situations and are thereby able to maintain crash risks that are comparable to those of younger drivers.

Keskinen, Ota, and Katila (1998) and Hakamies-Blomqvist (1996) consider the possibility that many accidents involving older drivers are in fact due to their defensive and slower driving, combined with faster driving by younger drivers. These young drivers may actually cause the accidents, although the older driver is often considered at fault in the accident report. One study assessed the behavior of young (<30), middle aged (30-60), and older (over 60) drivers while turning at intersections (Keskinen et al., 1998). It showed that older drivers took longer to make a turn across traffic (which were in this case right turns, as the study was conducted in Japan). This left less time for the oncoming vehicles compared with cases in which a younger driver drove the turning vehicle.

Driver self-regulation seems to be an effective way to alleviate some of the problems that arise with age. However, it is by no means perfect. For example, in studies on visual field deficiencies one study found that 56.7 percent of the participants who had abnormal visual fields were unaware of the problem (Johnson and Keltner, 1983). In another study 48 percent of the participants for whom a test showed visual field loss had not been aware of the problem before the test (Bengtsson and Krakau, 1979). Apparently some drivers are unaware of their limitations and may fail to take the proper precautions. This problem is particularly severe for older drivers with dementing diseases, such as Alzheimer's disease. Their limited capability for judgment makes it impossible for them to adjust their driving to their impairments.

NEW TECHNOLOGIES AND THE OLDER DRIVER

Until quite recently, innovations in cars were mainly related to the physical aspects of vehicle design, propulsion, and control. Over the past few years, new technologies have been introduced into the car that affect driving and the driver's actions in the car. The new devices with which drivers directly interact can broadly be divided into three categories:

Vehicle control devices are immediately tied into the perceptual-motor cycle of vehicle control. One group of devices enhances the sensory capabilities of the driver, for example, by providing visual information that may otherwise be less available. Examples are night vision systems, as are currently available in various high-end cars, and rear-view or blind-spot cameras that display views of the surroundings of the car on dedicated monitors. In the future there may also be enhanced-vision systems that superimpose images or icons on a visual scene so that, for example, a car with which there could be a possible conflict receives some visual salient marking that makes it easier to detect and to follow. Other devices that provide critical information are various forms of alerts and warnings, such as collision warning systems. Some devices that are already installed in cars or are developed take an active part in the control of the vehicle. Examples are adaptive cruise control systems that adjust vehicle acceleration and deceleration to the distance from other vehicles to maintain a constant headway.
Driving assistance devices provide the driver with information that is relevant for driving but does not immediately affect vehicle control. The information can be useful for the driver, but it is usually not safety critical. Examples of such devices are traffic information systems and navigation systems.
Driver infotainment and comfort devices provide entertainment for the driver and other occupants of the car, allow communication, or support driver comfort. These devices are unrelated to the driving task itself. They do, however, engage some of the driver's attentional capacity and can thereby indirectly affect driving. Examples of these systems are car entertainment systems, cellular phones, e-mail, web access, and climate control in the vehicle.

These three categories of devices are not necessarily installed as separate pieces of equipment. Instead, the general trend in the industry in recent years is to integrate a number of different devices in one entity, for example, using a single display and control unit for communication, entertainment, and navigation systems.

Some of the new technologies that are introduced into the car can have particular value for older drivers, considering that they can alleviate some of the effects of age-related changes. This can facilitate driving, allowing older people to drive in conditions in which they may otherwise have refrained from driving. These devices can also make driving safer for an older person by improving the protection in case of an accident and lowering the risk for accidents (Coughlin and Tallon, 1999).

Other systems (such as entertainment and communication systems) are not intended to help with driving. These systems often have no special value for older drivers. However, these devices are also installed in the older driver's car and need to be designed in view of the characteristics of older users if they are to be of any use for them.

Design of Technology for Older Drivers

The introduction of new technologies for older drivers should be based on the notion of “user-centered design” (e.g., Owens, Helmers, and Sivak, 1993). It requires the entire design process to be driven by the attempt to address the needs of the user and to adapt the product to the user characteristics. Usability considerations are of major importance for consumer acceptance and satisfaction with almost all consumer products. However, in the context of in-vehicle technologies they are particularly important because of the inherent safety issues related to these devices (Flyte, 1995). Below I provide a brief overview of some of the major design issues relevant for older drivers. Of course, the design for an older user will often improve a device for all users, regardless of age.

Physical Design

The physical changes that occur with aging should be considered when designing a car that can accommodate older drivers and passengers. At one level, the increased fragility of older drivers and passengers requires the design of safety systems that are adjusted to their specific needs. Seat belts, precrash seat belt tightening and seat adjustment, and airbags should adapt automatically to the weight and height of the person occupying a seat. Such measures can potentially lower the severity of injuries for older drivers.

In normal use of the car, steps should be taken to facilitate ingress and egress. Turning seats and large doors can help with this. Considering the increasing number of older adults in the population who not only drive but also often ride as passengers in cars, such design changes are likely to have definite appeal to a large section of the population.

It is also possible to use technological solutions to help cope with age-related physical difficulties. One problem that many older drivers experience is limited ability to rotate the neck and upper body, making it difficult to look to the side and back when backing up. A rear-view system that displays a wide-angle view of the area behind the car can help an older driver back up safely. Another system that is already installed in many larger vehicles is a backup warning system that alerts drivers when they approach an object while backing up.

Visual Design

The visual design of the vehicle interior and of in-vehicle devices should take into consideration the changes in vision that occur with age. As mentioned above, lowered acuity and contrast sensitivity are common among older drivers. The contrast between display elements and the background should therefore be maximal. Displays should use digital or analog indicators that are at a brightness level that differs as much as possible from the background. It is also beneficial to provide adequate lighting of the information and to avoid reflectance. The introduction of digital displays into the car makes it possible to adjust the display properties to the needs of the individual driver. The same “real estate” in the driver's field of view can be used to present more detailed information for a younger driver and less information (in larger displays) with greater contrast for an older driver.

Older drivers also benefit from relatively low-tech improvements in the car that can help alleviate some aging-related changes. For example, providing better lighting can reduce some of the problems with night vision. This can be done by improving headlights, which should be designed to illuminate longer stretches of road while lowering the likelihood of glare (Shinar and Schieber, 1991). In addition, a simple headlight washing device that helps to remove dirt from the lights and restore their full lighting potential will have particularly great benefits for older drivers (Mortimer and Fell, 1989). Using more-sophisticated technologies, older drivers can benefit from the augmented vision in darkness that is provided by night vision systems, such as GM's infrared system. Such systems can help older drivers extend their driving beyond daylight and maintain mobility in limited visual conditions. However, these systems can also cause new problems, in particular for older drivers. For one, the position of the displayed image may require the driver to accommodate to a closer distance, a process that becomes slower and more difficult with age. Also, the position of the image in the visual field differs from the position at which the image would usually be in the driver's field of view. This requires the driver to adopt new ways of visual scanning. This may be confusing, particularly for older drivers.

Auditory Design

Auditory displays are an alternative to visual information displays. However, hearing difficulties are fairly common among older adults, and they need to be considered when auditory displays are designed. Care should be taken not to create an overload in the auditory modality. This modality is relatively little used today in driving, but may become easily overloaded if a variety of devices, such as warning systems, cell phones, entertainment systems, traffic information systems, and navigation systems, provide the driver with various kinds of stimulation.

The properties of the auditory display should be adapted to the hearing abilities of the older driver. This is not a simple adjustment, because the loudness and frequency range of the displayed information should ideally be tuned to the existing acoustic situation in the car. When it is quiet, the windows are closed, and there is no source of auditory stimulation in the car, the displays can be less loud. Stimuli that are too loud will be perceived as annoying. Also, sudden loud stimuli could cause a startle response that may be dangerous. However, in conditions of strong auditory stimulation, such as when the driver listens to music or drives with open windows, the displays should be louder and adjust the information accordingly. The sound systems that present information from navigation, communication, or information devices should be individually tuned to the properties of a specific older driver's hearing. It may also be possible to improve the acoustic environment for hearing these messages, for example, by lowering the volume of all other auditory stimuli (e.g., the entertainment system) when a message is given.

Visual and auditory designs obviously need to go hand in hand. A recent study on the response to visual, auditory, and combined in-vehicle information systems by older (65-73-year-old) and younger (18-25-year-old) drivers showed that older drivers benefit from the use of multimodal displays that employ both visual and auditory modalities (Liu, 2000).

Cognitive Design

In addition to the more obvious sensory and motor aspects of aging that need to be considered when designing for older drivers, there are also cognitive aspects that must be addressed. The increasing availability of in-vehicle devices that provide the driver with various types of information can impose severe demands on the driver's attentional capabilities. The design of systems for older drivers needs to take into consideration the issue of information overload and allow the older driver to limit his or her information input as desired.

One important aspect of the cognitive design of new in-vehicle technologies for older drivers is mode awareness and situation awareness with respect to automated components (Sarter and Woods, 1995). For example, an adaptive cruise control system that adjusts the vehicle speed to the speed of another car in the same lane is actually a form of automation. It automates the driver's acceleration and deceleration required to maintain a constant distance from the car ahead. To use this system safely the driver needs to be aware of the mode in which the system is at each moment in time. For example, the system can be turned on or off and, if on, it can be engaged or not engaged. Older drivers may have more problems maintaining appropriate mode awareness and may therefore find automated systems less reliable, more confusing, and less useful. As a result, such systems, even if they could be particularly useful for an older driver, can go unused.

Design of the Driving Environment

In addition to design changes in the vehicle that can make driving easier and safer for older drivers, there are also various changes in the driving environment that can be made and that can be very beneficial for older drivers. The Federal Highway Administration has recently published a report pointing to ways in which roadways, intersections, signs, and markings can be designed to help older drivers (Staplin, Lococo, Byington, and Harkey, 2001). Older drivers are particularly likely to benefit from improved lighting, especially at intersections. Signs and pavement markings should be large and clearly visible. Longer merge and exit lanes will make it easier to cope with fast-flowing traffic. Adjusting roadways to the needs of older drivers will obviously also benefit other drivers, especially in difficult driving conditions such as heavy rain and fog.

What Technologies Are Good for Older Drivers?

The brief discussion of design issues and technologies for older drivers should make it clear that the introduction of a new device into the car is not always easy and will not necessarily constitute an improvement. Some of the new technologies that are introduced into the car require the driver to change behavior patterns that have served the older driver for decades. This change may be difficult, and the need to adopt new behaviors may rob older drivers of one of their main advantages—the extensive driving experience they have acquired over the years.

The notion that a device makes sense on the drawing board does not ensure that it will have the desired effect once it is introduced into the car. A number of reasons make it difficult to predict the effects of introducing a new system.

Users Do Not Necessarily Accept Innovation

It is by no means assured that a technologically sound device that provides definite benefits for the user will eventually be adopted. The most effective protective system against injury in a crash is a properly fastened seat belt (e.g., Rivara, Koepsell, Grossman, and Mock, 2000). In spite of the fact that this was widely known, it took decades for seat belts to become accepted by the majority of drivers, and this only after major efforts on the part of government agencies involved with traffic safety.

Good Intentions, Bad Outcomes

It is also often difficult to predict how a device will affect driving, especially because the effects of new technologies can change greatly over time. Expectations based on preliminary testing during the development phase may be unjustified. For example, the antilock braking system promised to have major safety benefits, but the actual benefits turned out to be very small. In fact, the system had an initial negative effect on safety, and some time had to pass before the accident rate returned to its level before the system was introduced (Farmer, 2001).

There are at least four reasons why a system that should improve safety can yield smaller than expected benefits and may at times even lead to negative effects. First, users may not use the device correctly and therefore may fail to obtain the safety benefits (e.g., drivers with an antilock braking system may cease to apply force to the brakes when the system is active and the brake pedal vibrates).

Second, the introduction of a device can create a feeling of safety that can induce a person to take a greater risk than he or she would without the device. This notion is expressed in models, such as Wilde's (1988) risk homeostasis theory, according to which people maintain a fairly constant level of risk and expose themselves to greater danger when they are protected by some safety device.

Third, a device that should benefit older drivers may not have the desired effect because it does not fit the specific driving characteristics of older drivers. For example, because older drivers may be less likely to detect possible hazards (because of diminished vision, distraction, etc.), they should particularly benefit from warning systems that provide an alert for possible problems. Indeed, older drivers respond to in-vehicle warnings in the same way as younger drivers (Cottè, Meyer, and Coughlin, 2001). However, warning systems tend to have false alarms, and the proportion of false alarms out of all alarms increases as the driver becomes more cautious (Meyer and Bitan, 2002). To demonstrate this point, consider two drivers who drive with the same collision warning system. The system has a certain detection rate when a collision is genuinely imminent and a detection rate when a collision is unlikely, the so-called false alarm rate. One driver takes great risks and therefore has many near collisions. This driver will encounter frequent warnings, and most will be justified. This driver is likely to view the warning system as useful. The second driver is very cautious, and collisions can almost never occur. This driver will encounter fewer warnings, and most warnings will be false alarms. Consequently this driver will believe that the warning system has only limited value. Considering that older drivers tend to drive more cautiously than younger drivers, they are likely to experience an unacceptably high false alarm rate in warning systems, causing the system to appear annoying and leading to its eventual rejection.

Fourth, the user may develop new behavioral patterns following the introduction of the new technology. A backup collision warning system can serve as an example. Backup collisions are particularly likely when a person has difficulties turning the head, which is rather common for older drivers. The installation of such a system should help drivers avoid many of these collisions and should make driving safer. However, the system can also change the way a person drives. In extreme cases the user may come to back up without even bothering to look back, waiting for the warning system to cue them when to stop. This turns the warning system from being a safety device into a device for primary vehicle control. As long as the warning serves only as a safety device, a malfunction in the warning usually has no severe consequences. When the warning serves as the information source for vehicle control, its reliability becomes crucial and any malfunction can lead to an accident.

The complex interplay of factors that determine the outcome of the introduction of a new device makes it necessary to develop new models and methodologies to predict the user's reactions to a new technological system. It cannot be simply assumed that a certain system analysis that applies for the current use patterns of a device will also apply when the device is altered. The benefits that are to be expected from a new technology have to be considered very carefully. New technologies need to be evaluated over time, in conditions that are as close as possible to the actual use conditions, and with people who represent the future user population.

The evaluation of devices also must take into account that the device will not be used in isolation. Rather, combinations of devices will be installed in the car and can at times be used together. For example, the driver may use a cellular phone to contact a person whom he or she intends to meet and at the same time look at the navigational system to receive directions on how to get to the meeting. The joint use of devices may create interactions that affect the utility and safety of using each of the separate devices.

The prediction of the effects of new technologies is further complicated because more than the driver's response to a system needs to be considered when evaluating the likelihood of its successful introduction. Legal and political issues are also crucial. For example, no system is perfect, and even with a very good system some collisions may occur. Some of them will likely be blamed on the system, and the manufacturer may be held liable. In view of this possibility, the manufacturer may take various steps to lower the chances of litigation, but these steps may also limit the usefulness of the system. Thus, the introduction of these systems requires a careful analysis of all aspects of the use of such a system, an analysis that requires the development of adequate predictive tools.

CONCLUSIONS

The question of how to provide older drivers with the opportunity to drive for as long as possible, while minimizing the risks due to incapacitated and unsafe drivers, is a crucial topic that will require even more attention in the future. There are numerous topics that need to be addressed to adjust for the aging driving population. For one, it is still largely unknown what causes the differences between older and younger drivers. We need to obtain a clearer picture of age-related driving characteristics. In particular it may be important to see how these characteristics change over cohorts and which of these characteristics will persist in the future. Also, the diversity of older drivers needs to be better understood, and more information must be collected on driving with different levels of impairment.

At a second level we need to determine how we can change driving so that older drivers will find it easier to fit into the driving population. Some of the necessary means may involve training older drivers to become aware of age related changes and to cope effectively with safety issues. We may also want to consider changes in the driving environment. Some of these changes can be related to changes in the road infrastructure that will make it friendlier for older drivers. For example, older drivers tend to have difficulties making left turns across traffic. Left-turn traffic lights or the use of traffic circles can solve this problem. Also, at some places older drivers may have trouble merging with traffic because other drivers drive at excessive speeds. The use of traffic control devices to lower the speed of oncoming vehicles can help to cope with this problem.

In the design of in-vehicle technologies, we are facing many unknowns regarding the effects of these technologies on drivers in various situations. The design of the device, the allocation of functions to it, and the design of the interface all require a thorough understanding of the interaction between users and technologies. This goes clearly beyond current knowledge in this field. The empirical basis for our research needs to be expanded by collecting both field and laboratory data. In addition, researchers need to develop appropriate design methodologies that take into account the unique characteristics of the driving situations and the needs and properties of the driver. This will be particularly important for older drivers, who may have less ability to adapt to a nonoptimal design of the system. Finally, models of the use of the automation and devices are needed for predicting how users will respond to a certain system design. Such models will allow us to move from the unsystematic engineering of human-vehicle systems that is practiced today to a more systematic and model-driven technique that approaches the methods used in other fields of engineering.

The introduction of the new technologies into cars for older drivers also makes it necessary for car manufacturers to reconsider their roles. More attention will have to be paid to the familiarization of the new driver with the technologies in the car. The best ways to do this are still fairly unclear. Because the use of many new in-vehicle devices is not entirely intuitive, companies will need to invest resources in the training of users in order to teach them how to maximize the utility of the system and how to deal with adverse situations. This need for training is particularly important for safety-critical systems, which are usually used only rarely and in conditions in which a very rapid and almost automatic response is required. Training will be particularly important when the system requires the relearning of some well-established skills. This is likely to be a greater problem for older drivers who, on the one hand, have much experience with older systems, and who are, on the other hand, usually somewhat slower in the learning of new skills.

Possibly car sales will have to include the use of simulator or test track driving to teach the driver how to respond to different events with the complex technologies. In addition, older drivers in particular will need to have the technologies customized to their particular needs. Drivers themselves can do this, but, in all likelihood, optimal customization should be based on the objective evaluation of the individual driver's needs by a specialist. This will require the development and validation of techniques to determine the optimal configuration for a driver. Also, specialists for customizing cars to the needs of individual customers may have to be trained. It is unlikely that current sales personnel can be expected to do this job appropriately, unless they receive the tools and knowledge for this additional service.

Thus the introduction of new in-vehicle technologies for older drivers requires us to expand the boundaries of our knowledge and our understanding in a wide variety of fields. It is likely that the insights gained here will be important in various domains, beyond the design of vehicles. Thus, this may be an opportunity to develop some of the major technologies for the twenty-first century, while helping an increasing number of people maintain independence, involvement, and quality of life.

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Bookshelf ID: NBK97349

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