confidence in, and self-rating of, driving ability among older drivers

Pergamon

PIhSO001-4575(97)O0100-O

Accid. Anal. and Prev., Vol. 30, No. 3, pp. 331 336, 1998 © 1998 Elsevier Science Ltd. All rights reserved

Printed in Great Britain 0001-4575/98 $19.00 + 0.00

CONFIDENCE IN, AND SELF-RATING OF, DRIVING ABILITY AMONG OLDER DRIVERS

RICHARD A. MAROTTOLI 1'2'* and EMILY D. RICHARDSON 3

1Department of Medicine, VA Connecticut, Geriatrics, 111C, 950 Campbell Avenue, West Haven, CT 06516, USA,

2yale University School of Medicine, Geriatrics, DC 023, 20 York Street, New Haven, CT 06504, USA and 3Department of Medicine, Yale University School of Medicine, Geriatrics, TMP 15, 20 York Street,

New Haven, CT 06504, USA

Abstract Active drivers (n = 125) in a representative cohort of older individuals age 77 years and older in New Haven, Connecticut were interviewed. Confidence in different driving situations, self-rating of driving ability, and driving patterns were assessed during these in-person interviews. A history of crashes, moving violations and being stopped by police was available for approximately the past 6 years. Concurrent driving performance was assessed in a subsample (n = 35). Analyses focused on determining the relationship of confidence and self- rating of driving ability to: (1) each other; (2) driving patterns; (3) adverse driving events; and (4) driving performance. All participants rated themselves as being average or above average drivers compared to others their age, with the majority rating themselves as above average. Individuals who drove more miles and more frequently were more likely to rate themselves better drivers than same-age peers. Individuals who rated themselves as "much better" drivers than their peers tended to have higher confidence levels than those who rated themselves a "little bit better" or the "same" as other drivers. On-road driving performance and history of adverse events were not associated with self-ratings of driving ability. Confidence was associated with driving frequency and mileage, but not age or education. Although men were more likely to drive under risky conditions, for those conditions in which each drove, men and women were equally confident. No relationship was found between confidence and adverse driving events or driving performance. Understanding the relationship of confidence and self-rating of driving ability to driving patterns, adverse events and driving performance may provide additional insights into identifying older drivers at increased risk for problems and formulating intervention strategies to help lower risk. © 1998 Elsevier Science Ltd. All rights reserved

Keywords Traffic accidents, Automobile driving, Elderly

I N T R O D U C T I O N

The number of older drivers in the U.S.A. is increas- ing. There were ca 22 million licensed drivers age 65 years and older in the U.S.A. in 1990; it is esti- mated there will be 33 million licensed drivers age 65 years and older by 2020 (Retchin and Anapolle, 1993). Concern has been raised because the mileage- adjusted crash rates of older drivers are higher than most other age groups, as is their likelihood of being injured, hospitalized or killed as a result of a crash (Barancik et al., 1986; Evans, 1988; Williams and Carsten, 1989).

Numerous earlier studies have attempted to identify medical conditions or functional impairments that may affect driving performance or crash risk

*Corresponding author. Tel.:001 203 688 3344; fax: 001 203 688 4209; e-mail: [email protected]

331

among older persons. Impairments of visual, cognitive and physical ability have been linked to driving performance and crash risk, as have medical conditions such as cardiac disease, dementia, diabetes, Parkinson disease, seizure disorders and stroke (Crancer and O'Neall, 1970; Fitten et al., 1995; Friedland et al., 1988; Hansotia and Broste, 1991; Johnson and Keltner, 1983; Klein, 1991; McLay, 1989; Owsley et al., 1991; Waller, 1967; Wilson and Smith, 1983). Research efforts continue in order to identify the subset of older drivers at greatest risk for safety problems so that interventions can be developed to lessen this risk.

However, the success of these interventions will be dependent on the ability of drivers at risk to recognize the problem so that they are willing to undergo the prescribed intervention. Two elements that may affect their ability to recognize a problem

332 R.A. MA~OTTOLI et al.

and adjust accordingly are their own ratings of, and confidence in, their driving ability. Confidence is a belief in one's ability, while awareness is the ability to perceive one's limitations. Lack of confidence in a given driving situation, such as driving in rush hour traffic or at night, may prompt one to avoid those circumstances. Similarly, awareness of one's limitations (e.g. night blindness) that can contribute to driving problems or awareness of driving problems themselves should prompt an individual to restrict or curtail their own driving. Lack of awareness is a discrepancy between one's perception of ability and actual ability. Awareness is critical to understanding one's limitations and to function accordingly (McGlynn and Schacter, 1989; Richardson and Nadler, 1995). Individuals who lack awareness of their abilities and limitations may engage in behaviors that compromise their safety and the safety of those around them.

Little is known about how confidence and awareness interact to affect driving safety. The aim of this study was to begin exploring this relationship in a community-based cohort of older drivers. Older drivers' confidence in, and self-rating of, their driving ability were assessed and analyses conducted to determine if these factors were related to each other, to driving patterns, to crash or violation history and to driving performance. It is hoped that increased understanding of this relationship will lead to interventions that enhance safety and that help clinicians to advise older drivers about the need to continue, limit or stop driving.

M E T H O D S

Participants Participants in the study were drawn from the

Project Safety cohort, a probability sample of community-living persons age 72 years and older in New Haven, Connecticut initiated in 1989. The sampling technique was similar to that used to establish the New Haven Established Populations for Epidemiologic Studies of the Elderly (EPESE) cohort (Cornoni-Huntley et al., 1993) and has been described in detail elsewhere (Tinetti et al., 1993).

All surviving cohort members who indicated that they were driving in the third interview (1992-1993) were contacted by phone in July 1994 to update their driving status. All 165 persons who were actively driving at that time were eligible to be included in the current study. In-person interviews were subse- quently completed between October 1994 and July 1995 on 125 active drivers. Of the remaining individuals, four had died since the July 1994 phone contact, 11 had moved permanently out of state, eight had

stopped driving, ten agreed to a partial phone interview and seven refused to participate. The 125 participants who completed the interview had a mean age of 81.4 years, a mean of 10.9 years of education, a mean Mini-Mental State Examination score of 26.6 (Folstein et al., 1975), and 57% were male.

Data collection The in-person interviews were conducted in

participants' homes, by trained research associates blinded to the study question.

Self-rating of driving ability. Participants' self- rating of their driving ability was ascertained by asking in a yes/no format whether they had driving problems, characterized by having got lost, received moving violations, got into accidents or had near misses in the recent past. In addition, participants were asked to rate their driving ability compared to other drivers their age. Answer choices included "much worse", "a little bit worse", "the same", "a little bit better" or "much better" than other drivers their age.

Confidence. A scale was developed to assess participants' confidence in their driving ability, which was derived in part from a driving questionnaire developed by Seeman et al. (1995) and from questions used in our earlier studies (Marottoli et al., 1993; Marottoli et al., 1994). The Driving Confidence Rating Scale assessed participants' level of confidence in driving on a scale of 0 (not at all confident) to 10 (completely confident) for each of 10 driving conditions: at night; in bad weather; in rush hour or heavy traffic, on the highway, on long trips, changing lanes on a busy street, reacting quickly, pulling into traffic from a stop, making a left turn across traffic and parallel parking or backing into a space between cars. A total score was derived by averaging the responses on the ten items.

Driving patterns. The Driving Practices Survey was used to obtain detailed information on participants' driving practices at the time of the study, including frequency of driving, average number of miles driven per week and conditions under which the participant did or did not drive. This survey was based on questions used in our prior studies (Marottoli et al., 1993; Marottoli et al., 1994). Driving frequency was defined by participants' esti- mates of how many days they drove and how many miles they drove in an average week (asked separately for the winter versus the other three seasons). Also ascertained was the frequency with which participants drove under specific conditions: at night; in rush hour or heavy traffic; on the highway; in unfamiliar areas; in their neighborhood; outside their neighborhood; outside their town; to other parts of the state; and

Driving ability and confidence self-rating 333

outside the state. These were answered by participants on a three-point scale ranging from "never" to "once a week or more".

Adverse driving events and driving performance. Participants' history of being involved in a crash, receiving a moving violation or being stopped by police was ascertained by self-report at each of five interviews (1989-90, 1990-91, 1992-93, July 1994, current interview) and covered the time period from 1 year before the first interview until the current interview date. A subset of the driving cohort (n= 35) participated in an on-road test of driving performance conducted by an experienced driving therapist who was not aware of the participant's performance on the test battery. The road test required the participant to make parking lot maneuvers and to drive on low-traffic suburban roads, in downtown traffic, and on limited access highways. The road course was 20 miles long and took ca 45-60 min to complete. All evaluations were done on a weekday at the same time of day and were rescheduled in the event of inclement weather. All evaluations were conducted using the same dual brake-equipped vehicle. The road test was graded on a 36-item scale that assessed a range of abilities and situations, such as speed regula- tion, vehicle position, lane changes, merging, turns, observance of signs and signals, interaction with traffic and operation of vehicle controls. Each item was scored on a three point scale ranging from major errors/unsafe performance (0 points) to minor errors (1 point) to no errors/good performance (2 points). Standardized scoring criteria were developed for each item prior to initiation of the study. In addition, the therapist provided an overall performance rating: no difficulty; minor difficulty; moderate difficulty; or major difficulty affecting driving safety.

Analysis The analysis focused on determining the relation-

ship of confidence (Confidence Rating Scale score) and self-rating of driving ability (reporting of a driving problem, self-rating of driving ability) to: ( 1 ) each other; (2) driving patterns; (3) history of adverse driving events (crashes, moving

violations or being stopped by police); and (4) driving performance (on-road driving perfor-

mance score). Pearson product-moment correlations were com-

puted to determine the relation among continuous measures (confidence scores with driving frequency/ mileage, age, education and driving performance score). Z 2 tests were computed to infer the relations among categorical variables (self-rated driving ability and report of driving problems with gender and with

history of adverse driving events). Analyses of vari- ance (ANOVAs) and t-tests were calculated to test for between-group differences as follows: one-way ANOVAs were computed to test for differences among self-rated driving ability categories in: (1) demographics (age, education); (2) average number of miles driven; and (3) confidence scores. Student's t-tests were computed to test for differences in Confidence scores based on: ( 1 ) gender; and (2) history of adverse driving events.

R E S U L T S

The characteristics of the driving cohort (n = 125) and the subset who participated in the substudy of driving performance (n=35) are depicted in Table 1. Of the 125 drivers in the cohort, 50 (40%) reported a history of a crash, moving violation or being stopped by police in an average of 5.76(_+0.25)years before the current interview. Among the 35 participants in the driving performance substudy, the mean score on the 72 point driving performance scale was 63.0 with a standard deviation of 13.0, a median of 69, and a range of 14-72. For the 33 participants with a therapist rating of overall performance, 24 (73%) had no or minor difficulties, whereas 9 (27%) exhibited moderate or major difficulties on the road test.

Self-rating of driving ability Reporting of events. Men were more likely than

women to acknowledge having often got lost, having had moving violations, crashes or near misses [Zz(1)=4.16, p <O.05].

Self-rating of driving ability. In terms of self- rating of driving ability relative to same-aged peers, none of the 125 participants rated themselves as being worse than other drivers. The majority (43.5%) rated themselves as being "a little bit better than", 32.3% rated themselves as being "the same as", and 24.2% rated themselves as being "much better than" other drivers their age.

Table 1. Participant characteristics

Driving cohort Performance substudy (,7 = 125) (n =35)

Age ( years)* 81.44 _+ 3.27 80.23 + 3.02 Male (%) 57 69 African American (%) 11 14 Education (years) 10.85 _+ 3.61 11.89 ± 2.95 M MSE Score 26.62 _+ 3.27 27.60 _+ 2.19

*Mean +standard deviation.

334 R.A. MAROTTOLI et al.

Demographics and driving patterns. Individuals who drove more miles were more likely to rate themselves as being better drivers than their peers [F(2, 121)=4.42, p<0.05] . Self-ratings of driving ability were not associated with age [F(2, 121) = 0.83, p>0.40] or gender [Z2(2)=3.15, p>0.20] .

Adverse event history. There was no association between self-rating of driving ability and history of adverse events. Of the 50 individuals with a history of an adverse driving event, 34 (68%) rated themselves as being better or much better than other drivers their age, which is identical to the proportion of individuals who rated themselves as better or much better drivers among those without a history of adverse events.

Driving performance. There was no difference in the frequencies of these ratings between those who did (n=35) and those who did not (n=90) undergo the on-road driving performance evaluation suggest- ing that participation in the performance substudy was not limited to drivers with high self-ratings of ability. Among those who participated in the on-road driving performance evaluation, self-rating of driving ability was not associated with driving performance score [F(2, 32)=0.67, p>0.50] . Moreover, all nine individuals rated by the driving therapist as having moderate or major difficulties on the road test rated their driving ability at least as good as their peers and indeed three of nine (33%) rated their ability as better or much better than same-age persons. In addition, seven (78%) of these nine individuals also had a history of an adverse driving event.

Discrepancy in self-rating. Individuals with a discrepancy in self-rating of ability were defined as those who rated their driving ability as better than their peers yet who had a history of an adverse driving event or a therapist rating of moderate or major difficulty on the road test. Of the 125 drivers, 34 (27%) had a discrepancy by these criteria. Such individuals were slightly older (mean age 82.26 +_ 3.88 versus 81.13 _ 2.98 years) and reported higher confidence scores (mean score 65.73_+18.48 versus 61.55 _+20.81 ) than other drivers in the cohort.

Confidence Self-rat. ing of driving ability. Individuals who

rated themselves as being "much better drivers" than other persons their age had higher Confidence scores (mean 76.70, SD 18.23) than did individuals who rated themselves as "a little bit better" than their peers (mean 62.85, SD 17.12), who in turn scored higher than those who rated their driving "the same as" other drivers their age (mean 52.53, SD 19.56) [F(2, 121)= 15.10, p<0.0001].

Demographics and driving patterns. Confidence scores were significantly correlated with driving frequency (r=0.31, p <0.0005), but were not associated with either age (r = - 0.13, p > 0.15) or education (r = 0.05, p>0 .60) . There was no association between confidence and gender, as women and men were equally confident in their abilities for those conditions under which they drove [t(123)=1.63, p>0.10] . However, men were more likely than women to drive in riskier conditions [t(123) = 2.97, p < 0.005].

Adverse event history~driving performance. Among the 125 drivers, Confidence Rating Scale scores did not differ between those individuals who did (n = 35) versus those who did not (n = 90) undergo the on-road driving performance evaluation. Confidence levels were not associated with either a history of adverse driving events [t(123)=0.01, p>0.50] or on-road driving performance scores ( r= 0.11, p >0.50).

D I S C U S S I O N

These findings suggest that confidence in, and self-rating of, driving ability are closely related to each other and to driving frequency, but not to demographic features, history of adverse driving events or driving performance (the latter finding must be interpreted cautiously given that only 35 persons participated in driving performance tests). Despite the fact that 40% of the cohort reported a history of adverse events, and 27% of those participating in the driving performance substudy were rated by the driving therapist as exhibiting moderate or major difficulties, all drivers rated themselves as being average to above average drivers. Similarly, drivers were confident irrespective of on-road performance and/or event history. Thus, objective evidence of driving ability (performance or event history) did not appear to impact on a driver's confidence or self-rating of abilities among this sample of older persons.

For the most part, these findings are consistent with earlier studies. Svenson (1981) found that two groups of students rated themselves as more skilful and less risky drivers than others in the experimental group. Holland (1993) reported that this "self-bias" was less apparent among older drivers than younger drivers. However, when comparing themselves to drivers aged 30, 50 or 70 years, drivers aged 70 years and older rated themselves least likely to have a crash compared to the average 70-year-old driver. McCormick et al. (1986) found that most drivers in their sample rated themselves better than average drivers along scales of eight characteristics potentially relevant to driving. They did not find differences in ratings by demographic characteristics. Similarly,

Driving ability and confidence self-rating 335

McKenna et al. (1991) found that drivers in their sample tended to rate themselves higher than the average driver. Although some discrepancies between men and women were noted, these were essentially eliminated when adjusting for driving experience. Groeger and Brown (1989) also did not find much difference in self-ratings of ability with age or gender if adjusting for driving experience. Of note, Matthews and Moran (1986) noted a trend toward lower self- ratings of driving ability and higher prediction of future crash risk among drivers with prior crashes, which we did not see in the current study. This trend was most notable among persons with multiple prior crashes. Preston and Harris (1965), however, found no difference in self-rated driving performance between drivers hospitalized for crash-related injuries and matched controls without histories of adverse events.

Among the strengths of the current study is its use of a cohort of drivers drawn from a representative population of elders and a sample that is older than those used in earlier studies of drivers. The primary limitation of the study is the small number of drivers (and even smaller subset that participated in the driving performance evaluation) which may have hampered our ability to detect an association between confidence or self-rating of ability and event history or driving performance. Other limitations include the geographic localization of all participants in a northeastern urban locale, which might limit the generaliza- bility of the findings, and the lack of comparison data from younger drivers.

We also lacked information on the nature and circumstances of crashes. Thus, the designation of a "discrepancy" may not hold for individuals with a high self-rating of ability and a very minor event or one where they were not at fault. However, for the subset of individuals who did poorly on the driving performance test yet rated their ability highly, this discrepancy is indicative of a lack of awareness. It would be helpful in future studies to have more detailed information on the nature of events to more accurately classify individuals with a discrepancy between self-perception of ability and actual driving performance and event history. This may be an important group to target for interventions given that persons who overrate their ability and have corre- spondingly high confidence levels in varying driving situations may exceed their limitations and place themselves and others at risk.

This study is a preliminary step in understanding the role of confidence and self-rating of ability in driving safety among older drivers. If the factors that contribute to these can be better understood, it may be possible to design interventions to enhance confi-

dence and awareness to help drivers improve safety or more appropriately adjust driving practices to match their functional limitations and driving capabilities.

Acknowledgements Funding for this study was provided in part by the Claude D. Pepper Older Americans Independence Center at Yale, the AARP Andrus Foundation, and the National Institute on Aging (AG 07449). Dr Marottoli is the recipient of a Veterans Administration Health Services Research and Development Career Development Award and a Paul Beeson Physician Faculty Scholars in Aging Research Award.

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