Psychometrics of the Self-Report Safe Driving Behavior Measure for Older Adults

Abstract

We investigated the psychometric properties of the 68-item Safe Driving Behavior Measure (SDBM) with 80 older drivers, 80 caregivers, and 2 evaluators from two sites. Using Rasch analysis, we examined unidimensionality and local dependence; rating scale; item-and person-level psychometrics; and item hierarchy of older drivers, caregivers, and driving evaluators who had completed the SDBM. The evidence suggested the SDBM is unidimensional, but pairs of items showed local dependency. Across the three rater groups, the data showed good person (³3.4) and item (³3.6) separation as well as good person (³.93) and item reliability (³.92). Cronbach's a was ³.96, and few items were misfitting. Some of the items did not follow the hypothesized order of item difficulty. The SDBM classified the older drivers into six ability levels, but to fully calibrate the instrument it must be refined in terms of its items (e.g., item exclusion) and then tested among participants of lesser ability.

Comparing Caregiver and Clinician Predictions of Fitness to Drive in People With Alzheimer’s Disease

“…A number of reasons have been put forth to explain reporter bias in caregivers, including the desire to avoid interpersonal conflict or to deemphasize the progression of the disease because of reliance on the driver for transportation (Wild & Cotrell, 2003). In a study of 80 older drivers, 33% stated that their independence would be affected if their spouse stopped driving, even though they were all licensed drivers (Classen et al, 2012a). In addition, because caregiving for a person with Alzheimer's disease requires providing support in many activities of daily living, spouses may not see poor driving skills as being as problematic as other dementia-related behaviors (Pinquart & Sörensen, 2011).…”

“…Studies using global ratings of driving fitness found that although caregivers were more stringent than people with AD, their ratings did not relate significantly to performance on a standardized road test given by a professional driving instructor Hunt et al, 1993). Studies using specific questionnaires to assess caregiver reports of driving skills and behaviors, such as the self-report Safe Driving Behavior Measure, have shown significant agreement between driving evaluators and caregivers (Classen et al, 2012a(Classen et al, , 2012b. Although caregiver ratings may be more reliable predictors of driving performance than self-report ratings, they generally are not as accurate as a clinician's global impression.…”

Concurrent Criterion Validity of the Safe Driving Behavior Measure: A Predictor of On-Road Driving Outcomes

“…Generally, we wanted to minimize misclassification of drivers, or false positives and false negatives. We generated the ROC curve and AUC estimates with PASW Statistics 18 using measures derived from raw scores on the SDBM by means of Rasch analysis and presented as logits 1 (Bond & Fox, 2007;Classen et al, 2012a). Using the measure (logits), we present the ROC curves demonstrating five of these potential SDBM cutpoint measures.…”

“…Difficulty with the driving task was rated on a 5-point adjectival scale ranging from 1 (cannot do) to 5 (not difficult; Classen et al, 2010Classen et al, , 2012a. The family member and caregiver's SDBM includes only Sections A and C. In this study, we used scores from Section C (interval data derived from Rasch analysis), not the total of the raw scores (ordinal data) as documented in detail in Classen et al (2012a). We used the SDBM as the independent predictor of on-road outcomes.…”

“…Family members and caregivers were involved in establishing face and content validity (Classen et al, 2010;Winter et al, 2011), and their ratings were used to determine construct validity (Classen et al, 2012a), rater reliability, and rater effects (leniency vs. severity) among three rater groups (older drivers, family members and caregivers, driving evaluators; Classen et al, 2012b). Our preliminary data (from the studies cited earlier) point to the SDBM's potential usefulness as a screening measure for family members or caregivers to rate the driving behaviors of older drivers, but concurrent criterion validity has not yet been determined.…”