By the year 2030, 70 million Americans will be 65 or older (AARP, 2004), and approximately 80 percent of this population will likely be driving themselves . Currently, the private automobile is the primary mode of transportation for older adults, as it is for other people. For many older people, driving is a necessity because the majority live in suburban or rural areas, where an automobile is often the only mode of transportation (AARP, 2005). This section examines the risk that older drivers pose to themselves and to others, and it also explores the consequences of driving cessation.
Based on crash rate per population group, older drivers are underrepresented. Older Americans are among the safest drivers on the road. They are involved in the fewest crashes, are more likely to wear seatbelts, and have the lowest rate of crashes due to alcohol impairment ( National Center for Statistics and Analysis, 2002). However, when driver safety is assessed in terms of crashes per miles traveled, drivers of the oldest age group (85+) are more likely to be involved in a crash than those in younger age groups (Marottoli, 1998). Thus, although the oldest drivers have less exposure on the road, they have more crashes per mile driven than other age groups (Massachusetts Institute of Technology AgeLab, 2003). Tokoro (2004) notes similarities to the United States in the lower levels of driving exposure among Japanese older drivers and suggests that researchers increase their efforts to understand how older people use cars in their daily lives and what safety strategies can be developed. Hakamies-Blomqvist, Wiklund, and Henriksson (2005) caution that linear projections of older drivers’ crash involvement, based on the growth of this age group and in anticipation of their increased presence in traffic, are likely to be overly pessimistic. These authors demonstrated that, compared to the crash involvement of the general population in Sweden, there was a relative decrease in older drivers’ crash involvement per licensed driver and per active driver in the period 1983–1999. However, once in a crash, drivers 70 and older are also more likely to suffer severe injuries, and they have the highest probability of being fatally injured (Langford, 2004a, 2004b).
The U.S. Department of Transportation (2003) reports that the rate of driver fatality per 100 million miles driven has begun to increase among the 55 to 59 age group. For the population 80 to 84, the rate has tripled. This is thought to be due in large part to elder frailty. Crash impacts that a younger person could survive may be fatal for older people simply because their bodies are more fragile and they are more likely to suffer from a pre-existing illness that may complicate medical treatment (U.S. Department of Transportation, 2003). The higher fatality rate may also be partially due to the types of crashes that seniors are more likely to experience, such as side-impact crashes at intersections. Langford (2004b) believes the higher fatality rate may also be due to elderly individuals having problems with gap selection, traffic complexity, high speeds, high traffic volume, and restricted sight distance.
A recent AARP survey (2005) found that most of the Nation’s older population lives in rural or suburban settings, and this pattern is expected to continue as baby boomers age. Rural areas and the areas close to home that older drivers frequent are the most common sites for crashes. Older people also rarely use highways and are more likely to travel across town in stop-and-go traffic, which presents a greater likelihood of crash involvement (AARP, 2004). Thus, older drivers are likely to drive in more dangerous settings than other age groups (AARP, 2004).
Dementia is thought to affect many critical abilities needed for driving, including perception and visual processing; the ability to maintain selective attention on particular stimuli for extended periods of time; the ability to attend to multiple stimuli at once; the ability to make correct judgments (such as which drivers have the right of way); and the ability to react appropriately when pressured in a traffic situation (Janke, 1994; Uc et al., 2004). In the early stages of their disease, individuals with dementia may be capable of driving under normal conditions since the mechanisms of vehicle operation are usually well established within their long-term memories. But the driver may have difficulty responding to new or challenging circumstances, and individuals in this stage are known to become lost while driving (Silverstein, Flaherty, and Tobin, 2002). They may stop scanning their surroundings and instead focus on looking straight ahead. As an individual progresses into moderate impairment, the ability to drive competently is highly compromised, as is insight into the driver’s level of skill impairment (Janke, 1994; Anstey, Wood, Lord, and Walker, 2004). People with severe impairment are usually nonambulatory.
Studies relating the yearly crash rates of older Americans with dementia to those of healthy older Americans generally show an inflated crash rate for those with dementia (Hunt, 2003; Janke, 1994; Marottoli, 1998). However, such studies are often done with a small number of participants and therefore have limited generalizability. While caution should be exercised in interpreting these studies, a pattern of concern is nevertheless emerging. Researchers at Washington University in St. Louis estimated that approximately 30 percent of demented drivers would have a crash under normal driving circumstances at some point during the moderate stages of the disease, leading to the conclusion that there is an increased risk to public health (Morris, 2004). The crash risk was shown to be related to the duration of the disease and to gender. Specifically, men in the moderate stages of the disease were shown to be the most unsafe. A study conducted by the California Department of Motor Vehicles, using male drivers only, demonstrated that men with AD are less likely than men without AD to assess their driving skills accurately and that their caregivers are less likely to recognize the problem (Janke, 1994). Such studies also report that individuals with dementia are less likely than healthy older drivers to realize that their driving is unsafe. The Washington University study found that approximately 50 percent of individuals ceased driving within three years of diagnosis. Whether such cessation was voluntary was not explained; however, given that loss of insight is common, it is unlikely that drivers with Alzheimer’s disease or related dementias would stop driving solely because of self-assessment.