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...please, but many others continue drive out of necessity (Orr, 1991). Data indicate that some older drivers often continue to drive because of a lack of adequate public transportation within their community and the fear of isolation or of being a burden to others if they gave up driving (Orr, 1991).
However, older drivers are often depicted in the movies and on television as slow drivers, accident prone, and a driving risk to self and others. It is true that older drivers, as a group, have more traffic accidents and more fatalities per miles driven than all other groups except young drivers; however, one should consider that a wide range of individual differences in driving capabilities exists among older drivers. Ball et al. (1998) suggested that because such wide variability does exist, only a subset of older drivers--those with severe functional impairments--increase the average risk of an accident for the entire age group.
This depiction of older drivers as a driving risk to self and others has led governing bodies and many within the public sector to question whether an upper age limit or other restrictions should be imposed on driving. Some state legislatures have considered denying drivers' licenses to individuals who exceed a particular age. Additionally, some states are considering placing restrictions (e.g., specifying under what conditions a person will be allowed to drive) on older drivers (Ball, Owsley, Sloane, Roenker, & Bruni, 1995). A few states now require an annual driver license renewal for individuals over the age of 60 (Federal Highway Administration, 1998). Howevel; Ball et al. (1995) wrote, "policies that restrict driving privileges based solely on age or on common stereotypes of age-related declines ... are scientifically unfounded" (p. 3110).
The majority of states require that drivers have a best-corrected visual acuity of 20/40 to obtain a nonrestricted driver's license. However, these visual standards vary from state to state: Kansas will grant a restricted driver's license to individuals with a best corrected acuity of 20/ 90, but California will allow an individual with a best corrected acuity of 20/200 (which is the legal definition for blindness) to obtain a restricted driver's licenses (Charman, 1985; Fishbaugh, 1995; Kansas Driving Handbook, 1999; Keltner & Johnson, 1987).
Only a limited number of studies have focused exclusively on the relationship between vision and driving (Ball et al., 1993; Fox, 1988; Keltner & Johnson, 1987; Kline et al., 1992; Kosnik, Sekuler, & Kline, 1990; Kosnik, Winslow, Kline, Rasinski, & Sekuler, 1988; Owsley et al., 1998). Results from many of these studies suggest, both directly and indirectly, that the vision problems that plague many older adults have some effect on their driving abilities. Kosnik et al. (1988, 1990) found that older drivers reported more difficulty with performing a variety of everyday activities (e.g., difficulty reading small print, difficulty distinguishing dark colors, eyestrain doing close work) because of their declining vision. These problems were more pronounced in older persons who had recently given up driving. Also, similar to Kosnik et al.'s (1990) results, Kline et al.'s (1992) results indicated that the vision problems experienced by current older drivers increased with age. Additionally, Kline et al. (1992) identified age-related visual declines along specific driving dimensions. Older adult drivers reported difficulty in estimating vehicle speed, viewing a dimly lit dashboard, and reading street signs. These participants also complained more about the unexpected appearance of vehicles (merging or passing) and windshield problems such as glare.
Ball et al. (1995) expanded the research parameters set forth by Kosnik et al. (1988) and Kline et al. (1992). Ball et al. (1995) examined the visual information-processing ability and other visual capabilities of adult drivers to determine whether a relationship existed between the participants' number of reported automobile accidents and their visual abilities. They examined six areas of visual function in an attempt to find a correlation between vision and crash history. The six visual capabilities examined were static visual acuity (the ability to detect details clearly in nonmoving objects), contrast sensitivity (one's ability to distinguish between an object and its background when the two resemble each other closely in color), glare, stereopsis or depth perception, visual field sensitivity (the necessary intensity of a presented object for perception), and color discrimination. The authors also measured the size of each participant's useful field of view. Ball et al. (1995) hypothesized that as the field of view decreases with age, so does the useful field of view. Unlike the researchers who preceded them, Ball et al. (1993) made an attempt to include individuals with poor vision (visual acuity worse than 20/40). Results from the study indicated that several of the visual measures were correlated with the size of an individual's useful field of view. However, the only indicators that correlated highly with crash involvement and discriminated well between crash-involved and crash-free drivers was the size of the useful field of view.
Although Kosnik et al. (1988), Kline et al. (1992), Ball et al. (1993), and others have acknowledged that vision changes as one ages, each of these studies excluded individuals with a diagnosed visual impairment, and none of them included individuals...
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