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Author: Richard Marottoli
The cessation of driving can have positive consequences for society but serious negative consequences for older people.
In recent years, the discussion of safe transportation for older people has expanded beyond driving to include a range of options for providing out-of-home mobility. In this context, the term “mobility” is not a synonym for ambulation but is used in a broader sense to mean how a person gets from one place to another outside the home. Many factors have influenced this paradigm shift. One of the most important was that limiting the discussion to who could still drive safely and how those who were no longer safe drivers should be evaluated and de-licensed addressed only part of the issue and left the larger, looming question of “what now” unanswered.
For people who have to limit or stop driving, there is a large void to be filled to mitigate the negative practical and psychological effects of no longer being able to drive. A detailed discussion of this issue, including research developments, practical applications, and future directions, can be found in Transportation in an Aging Society: A Decade of Experience (TRB, 2004) and a companion document, Safe Mobility for Older Americans: Report of the Committee for the Conference on Transportation in an Aging Society (TRB, 2005).
Still, the traditional emphasis on risk was understandable. Motor vehicle crashes are a leading cause of “accidental” injury and death in people 65 years of age and older, a group that is growing rapidly as the general population ages. Coupled with the increased susceptibility of older persons to injury because of their decreased reserve capacity, safety concerns are understandable.
However, the importance of driving to a person’s sense of independence and well-being must also be taken into account, particularly for people in North America. Older persons depend on cars far more than other modalities for transportation, either as drivers or passengers. Moreover, in our society out-of-home mobility provided by driving is a key factor in being able to participate in social and productive activities, which in turn have been associated with lower risk of mortality and better functional status (Glass et al., 1999). Indeed, the cessation of driving has been linked to a number of negative outcomes, including a decrease in participation in out-of-home activities, an increase in depressive symptoms, and possibly an increase in the likelihood of nursing home placement (Freeman et al., 2006; Marottoli et al., 1997, 2000).
A sense of these negative consequences, which has long been evident in clinical practice, has led to reluctance on the part of both patients and clinicians to discuss the topic or to assess the underlying risk factors of driving difficulties. In an early survey, many physicians reported that they were reluctant to address the issue because of the potential negative consequences for their patients and the lack of options in many locations to fill the mobility gap if people had to stop driving (Drickamer and Marottoli, 1993). Increasing awareness of the need to provide transportation options and make people aware of those options have been major contributors to the paradigm shift in thinking described above.
Although much of the early research in this area was on medical conditions and functional impairments that might contribute to safety risks, recent efforts have focused more on determining whether interventions to improve drivers’ functions or adapt to impairments might improve driving performance and safety. It is hoped that a combination of the availability of interventions, and evidence of their effectiveness, coupled with the availability and awareness of transportation options, will encourage drivers, families, and clinicians to engage in discussions of this sensitive topic and ultimately lead to a better balance between safety, autonomy, mobility, and participation in out-of-home activities.
Demographics and Travel Patterns
The number of older drivers is increasing, both because of the aging of the population as a whole and the relative increase in the population of older people, largely women, who continue to drive, as compared to women their age in the past. In the United States, the vast majority of trips by older persons, even of very advanced age, still depend on their driving, or being driven in, private automobiles (Rosenbloom, 2004).
Although the absolute number of crashes involving older drivers is low, crash rates increase when they are adjusted for mileage. Older individuals are two- to four-fold more likely to be injured, hospitalized, or killed (probably because of their decreased reserve capacity) than younger individuals in crashes of similar magnitude (Barancik, 1986; Fife, 1984). Motor vehicle crashes are the leading cause of “accidental” death for individuals 65 to 74 years old and the second leading cause for individuals 75 to 84 years old (Dellinger and Stevens, 2006). Not all injuries occur in crashes, however; older individuals sustain approximately 37,000 injuries a year getting into or out of vehicles, more than 40 percent of these due to falls (Dellinger et al., 2008).
Although advancing age per se does not increase the risk of crashes, certain older drivers are at risk because of functional limitations, medical conditions, or the effects of medication. Limitations in vision (distance acuity, peripheral fields, contrast sensitivity), cognition (visual attention, processing speed, visual-spatial ability, and executive function), and physical ability (flexibility and speed of movement) have been associated with poor driving performance or crashes, as have medical conditions such as cardiac arrhythmias, dementia, Parkinson’s disease, sleep apnea, and stroke (Decina and Staplin, 1993; Drachman and Swearer, 1993; Findley et al., 1998; Freund et al., 2005; Larsen et al., 1994; Legh-Smith et al., 1986; Marottoli et al., 1994, 1998; McLay, 1989; Owsley, 2004; Owsley et al., 1991; Whelihan, 2005).
Crashes involving older drivers are most likely to occur at intersections, particularly when making left turns across traffic (Griffin, 2004; Mayhew et al., 2006). Individuals who drive fewer than 1,800 miles per year also appear to be at increased risk, probably because of the circumstances in which they drive (urban areas with more traffic and intersections) and possibly because of functional limitations (Keall and Frith, 2006; Langford et al., 2006; Lyman et al., 2001). However, older people who drive more than 1,800 miles are often able to drive safely on highways and tend to have lower crash rates (Keall and Frith, 2004; Langford et al., 2006).
Effects of Driving Cessation
Several community-based studies (Campbell et al., 1993; Jette and Branch, 1992; Kington et al., 1994; Marottoli, 1993) have found similar risk factors for driving cessation: advancing age, female gender, poor health (either self-perceived or neurological or visual disorders), and functional limitations (in basic or instrumental activities of daily living or higher level physical activities). However, driving cessation in itself can also have negative consequences, including decreased participation in out-of-home activities, increased depressive symptoms, and increased risk of nursing home placement. The potential consequences of cessation, coupled with the association of participation in social and productive activities with lower mortality risk and better functional status, suggest that a potential downward spiral may be triggered in part, or compounded by, driving cessation.
Improving Medical Conditions and Functional Abilities
Growing evidence about risk factors and the negative effects of driving cessation have led to the development of a number of interventions to determine if driving safety can be enhanced and prolonged. Interventions focused on improving medical conditions or functional abilities have, in fact, demonstrated that driving safety can be improved. Successful interventions in this category include removal of cataracts, which can restore and improve vision and, hence, driving capability (Owsley et al., 2002); training to increase the speed of information processing, which can enhance activities of daily living, as well as driving performance (Ball et al., 2007; Roenker et al., 2003); and range-of-motion and speed-of-movement conditioning, which can enhance driving performance and control (Marottoli et al., 2007).
One approach to intervention focused on education is combined classroom and on-road driver training (Figure 1), which has been found to improve on-road driving performance and road awareness (Bedard et al., 2008; Marottoli et al., 2007b). Another approach has been to make people more aware of their functional impairments, which often results in their voluntarily driving less often and in less risky situations (Owsley et al., 2003).
Modifications to Vehicles
The interventions described above were focused on driver capabilities. However, other avenues for intervention include changes in the driver-vehicle and driver-roadway interfaces. In this regard, it is helpful to consider the Haddon injury matrix of factors that occur before, during, and after a collision involving the driver, vehicle, and roadway (Marottoli, 1993; Pike, 2004). Modifications that can help avoid collisions and injuries include making it easier for people to enter and exit the vehicle, designing seats for driver comfort and movement, making vehicle controls more visible to make interaction with them easier, improving outward visibility and the use of mirrors, ensuring the use of safety belts, and the presence of technologies such as antilock brakes and traction control.
In the event of a crash, the most important factors are safety belts and air bags, the structural integrity of the vehicle, and mechanisms that limit contact with hard vehicle surfaces. After a crash, important factors include automated signaling systems that alert emer-gency responders and technology that informs emergency crews of the severity of damage and the likely severity of occupant injury.
Modifications to Roadways
Because left turns across traffic are a particularly dangerous maneuver, many recommendations have been made for changes to intersection design to make these turns safer. Given the functional impairments com-monly encountered among older drivers, particular attention has been paid to designing intersections so that drivers making turns can see oncoming traffic clearly, that left-turn lanes are protected, that signs are easily visible, and that signals provide enough warning time for older drivers to respond (Schieber, 2004; Staplin, 2004).
FIGURE 1 Comparison of road test scores at baseline and three months for intervention and control groups.
Design strategies include having protected left turn lanes with a green-arrow signal and providing a “positive offset” at intersections that do not have green-arrow signals so that the turning vehicle is in a position to see oncoming traffic clearly before turning. Considerable efforts have also been made to modify signs and signals to reduce the risk of crashes and to protect pedestrians who must have adequate signals and traffic/speed control to allow sufficient crossing time (Langlois et al., 1997; Oxley et al., 2004).
Other roadway design changes that can reduce the risk of crashes, or minimize the risk of injury if crashes do occur, include removing fixed roadside obstacles, enforcing speed limits, lengthening merging lanes on highways, and using low-glare lighting, high-traction surfaces, and high-visibility lane markings and signs. Considerable efforts have also been made to use sign materials and letter fonts and symbols that maximize their visibility for all drivers under all conditions.
Other Transportation Options
As people limit their driving or stop driving altogether, they must rely on other transportation options to enable them to maintain out-of-home mobility and activity levels. A broad range of options may be available, depending on the person’s capabilities and limitations, geographic location (urban, suburban, or rural), and financial resources (Suen and Sen, 2004). Key features to be considered have been called the “five A’s of transportation”: availability, accessibility, acceptability, affordability, and adaptability (Kerschner and Aizenberg, 2004). Part of the challenge is identifying existing options in a given area and determining how many of the key features they have.
After private cars, the most common option in many areas is walking, highlighting the importance of pedestrian safety (Suen and Sen, 2004). Urban areas typically have affordable public transportation options, because shorter distances are involved and infrastructure is more extensive. In less densely populated areas, informal transportation must be relied upon.
Public transportation options (such as buses, subways, and rail) typically operate on fixed routes with set schedules and pre-determined stops; they sometimes also have a flexible route that can be modified for picking up and dropping off passengers. In addition, paratransit services, private taxis, and livery services may provide a range of options.
Land-Use Planning and Retirement
Another approach is to define how retirement and land-use planning interact (Giuliano, 2004). One area of focus in studies of decisions about where people decide to live and retire is how transportation-related factors enter into their decisions. Another factor is how communities adjust to the aging of their populations in terms of ensuring pedestrian safety and providing transportation options. In some cases, communities are designed from the outset to meet the needs of older persons.
Future Directions and the Role of Technology
At each juncture outlined above, there are many areas that need further investigation or that can be improved. Even though we already have substantial evidence of effective interventions, our knowledge in many areas is limited, and we surely must improve the efficiency and dissemination of information about successful interventions.
In addition, many uncertainties and variables are likely to change over time, such as the characteristics of vehicles and roads, as well as the capabilities and limitations of drivers and transportation users. We must keep an open mind and apply our existing knowledge with the overriding goal of keeping older persons as safe and mobile as possible.
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