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17 Strategies to Maintain Safety with an Aging Age-related deficits in contrast sensitivity may also be Driver Population remediated in many cases where this loss results from cat- aract formation. A reduction in crash risk following cata- Individual drivers, their employers, and society as a whole ract removal surgery has been demonstrated (Owsley et will benefit as new approaches are implemented to maintain al. 2002), including evidence that drivers with a cataract safety in an aging workforce. Initiatives in three broad areas who underwent surgery and intraocular lens implantation may hold promise in this regard: remediation, accommoda- had half the crash rate of drivers with cataract who did not tion, and prevention. undergo surgery (4.74 crashes per million miles of travel ver- sus 8.95); this effect is most likely attributable to improve- The first option centers on deficits linked to a specific ment in contrast sensitivity (Owsley et al. 2001). A study medical condition for which there is an intervention with by Wood and Carberry (2006) found that improvement in proven effectiveness. These interventions should general- contrast sensitivity after cataract surgery was the best pre- ize well to commercial drivers, allowing them to realize the dictor of improved driving performance during an on-road same benefits as those demonstrated for the general driving (closed course) test, which included the ability to detect and population. The second option targets individuals with iden- avoid hazards. Monestam and Wochmeister (1997) found tified deficits, employing strategies to help offset a particu- that more than 20% of older adults returned to driving after lar diminished capability to an extent that they can continue cataract surgery. Conversely, those (older) adults who delay to drive safely. The last option posits safety benefits from cataract surgery appear to be at greater risk of losing driving the use of validated screening tools to provide early warn- privileges (Leinonen and Laatikainen 1999). ing of age-related declines in key safe driving abilities, to improve the potential for remediation or accommodation, The potential to remediate other conditions that impair while identifying operators who need an in-depth medical vision is more limited. For MD, laser therapy can stabilize evaluation to allow determination of their health and/or job the condition in exudative cases, and certain medications status. Evidence keyed to commercial driving applications, have shown promise in actually improving vision for patients though limited, may be cited for the latter options. with this disease (Smith et al. 2007). For glaucoma, treat- ment can be either medical (eye drops) or surgical (laser); in Remediation either approach, the goal is to lower intraocular pressure, but the realistic expectation for these interventions is to slow the The option to remediate functional deficits tied to elevated progression of the disease rather than to remediate it. crash risk is a preferable option, where available. A com- prehensive review of countermeasure options targeting With regard to age-related physical limitations that have age-related functional decline completed in 2009 (Stutts et been linked to higher crash risk, it appears that deficits al. 2009) points to effective interventions for remediation resulting from certain chronic conditions may be remedi- of certain visual and psychomotor limitations experienced ated through strength and flexibility exercises. Significant by normally aging drivers. The remediation of cognitive improvements in trunk rotation and shoulder flexibility fol- impairment is more problematic, though recent studies offer lowing an 8-week exercise program led subjects measured some promise in this area. at baselines 8 and 11 weeks to look more frequently to the sides and rear of their vehicle than control drivers who did The most widely available, affordable, and effective not participate in the program (Ostrow et al. 1992). countermeasure to improve vision is a refractive correction. Although no beforeafter studies to measure the safety gains Marottoli et al. (2007) reported on a study in which older from this intervention could be identified, it may be advo- drivers received a 12-week program of in-home exercises cated simply based on the prevalence of the problem (acuity to do 15 minutes each day, 7 days a week, with a weekly deficit) and the inexpensiveness of the solution. One of the in-home visit by a physical therapist. Exercises focused on early findings of the Salisbury Eye Study was that among the axial/extremity condition, upper extremity coordination/ proportion of older individuals who had worse than 20/40 dexterity, and gait abnormalities. On-road driving perfor- vision, more than half of them could be corrected just with mance was measured at baseline and post-intervention for the glasses. A new development in this area also deserves men- treatment group and a control group. There was significant tion: wavefront lenses. This technology provides higher-def- improvement in the targeted physical abilities for the treat- inition vision in the daytime and can significantly improve ment group compared with the control group, which trans- driver responses under nighttime conditions. According to lated to an 8% to 16% lower crash occurrence over a 2-year research by the developer, drivers' ability to identify pedes- period. At follow-up, the intervention group also made 37% trians at night increased by an average of 330 msec, or 30 ft fewer critical errors (inattention, turning or changing lanes sooner at 55 mi/h, when using wavefront lenses compared without looking, disobeying traffic signs or signals) than the with conventional lenses (Haddrill 2008). control group.
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18 In the arena of cognitive remediation, there is preliminary dynamic visual acuity, contrast sensitivity, useful field of evidence that speed of processing training can yield sus- view, field dependence, depth perception, selective attention, tained gains in performance on measures of visual attention, attention sharing, information processing, decision making, that translate to improved performance behind the wheel. reaction time, multi-limb coordination, control movement Roenker et al. (2003) used a standardized on-road driving precision, tracking, and range of motion. A detailed descrip- course to compare the performance of older drivers who tion of the methodologies used to obtain these measures of completed a computer-based speed of processing regimen functional ability is presented in Llaneras et al. (1998). with two control groups on a number of risky maneuvers, including six opportunities for unprotected turns across traf- The study sample included 107 commercially licensed fic and nine left-turn entrances to a high-traffic road. The (current CDL) truck drivers in five age cohorts: under age controls were a placebo group and a group who completed 50, ages 50 to 54, ages 55 to 59, ages 60 to 64, and age 65 training on a part-task fixed-base driving simulator. After 18 and older. The age range in the sample was age 31 to age 76; months, the speed-of-processing training group maintained these subjects had an average of 27 years of driving expe- superior performance, compared with both control groups. rience, including both long-haul and local, and averaged The potential for this intervention to ameliorate crash risk 61,000 miles per year. More than a dozen companies plus a among normally aging (i.e., not demented) older drivers will number of independent owneroperators were represented be examined carefully in future research. in the sample. Accommodation Of the 15 abilities assessed for the study sample, 13 were found to degrade significantly with age. As a rule, differ- The accommodation of age-related functional deficits can be ences were greatest when comparing the under age 50 group accomplished through the use of in-vehicle aids, or through with the age 65 and older group. There were two notable education and training. In-vehicle aids compensate for a exceptions among the psychomotor tests and the cognitive diminished capability to execute some critical driving skill. tests. Test results for multi-limb coordination showed that A diminished sensory capability may be accommodated by the age 65 and older group had the best performance of any aids that make information more accessible to the driver; age cohort; more than any other measure, this may be related aids that prioritize information or otherwise reduce task to an integrated driving activity and the authors suggested demands may, to some extent, compensate for diminished that "experience may have compensated for any age-induced cognitive capability; and aids that assist in vehicle control decrements." Also, the results for decision making showed actions may compensate for certain physical limitations. that speed (measured by choice reaction time) decreases Training interventions, by comparison, are designed to significantly with chronological age, but accuracy does not enhance driver performance as the result of new knowledge decrease. Each of the perceptual abilities measured showed a or directed practice in a critical driving skill. decline with advancing age, with the strongest bivariate cor- relation (r = -0.51) between age and useful field of view. There is a vast literature describing adaptive equipment for private vehicles; the field of driver rehabilitation is among Driving performance data were collected using a TT150 the fastest-growing subdisciplines for occupational thera- Professional Truck Driving Simulator, configured as a cab- pists (see Stav et al. 2006). Similarly, reviews of programs over, tandem-axel tractor with a 48-ft trailer carrying an and techniques for commercial driver training are widely 80,000-lb uniform load with a high center of gravity. Struc- accessible (e.g., Staplin et al. 2004). But only a single inves- tured observations of driver behaviors (e.g., mirror checks, tigation has explicitly examined the efficacy of strategies to visual search, and speed control) by commercial drivers accommodate deficits in visual, cognitive, and psychomotor with 20 years of training experience, and performance mea- abilities known to influence performance or predict crash sures obtained automatically by instruments in the simu- risk among older commercial drivers (Llaneras et al. 1998). lator (speed and space management, fuel economy), were A detailed review of this study follows. collected as study participants drove a standardized 10-mile course. This course included a variety of road conditions and The Llaneras et al. study was designed to first evaluate the driving tasks, such as turns at intersections, straight driving independent effects of selected functional abilities on driv- along interstate highways and along two-lane rural roads, ing performance and safety, and then to develop and evaluate lane changing, and responses to hazards (a sudden loss of air interventions targeted to key abilities for which deficiencies brake pressure). are common among older commercial drivers. The emphasis on independent effects is important, as a deficit in any sin- Based on a step regression analysis using age and the gle ability that significantly predicts performance or safety results of the functional ability measures to predict scores outcomes can establish the need for a countermeasure, and on the driving performance measures obtained in the simu- provide a theoretical basis to guide its development. Specific lator, Llaneras et al. (1995) developed a model estimating abilities measured by the research team included static and the relative contributions of age versus functional change to
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19 an individual's overall driving skill and to performance on The results of this countermeasure evaluation study did discrete tasks such as negotiating curves, executing turns, not demonstrate benefits for every intervention on every shifting, and fuel management. Within this model, a hier- dependent variable. Drivers equipped with the automatic archical analysis of direct, indirect, and total effects asso- transmission had superior performance during negotiation ciated with age and with the strongest predictors within of curves, but worse fuel economy and higher brake tem- each domain of functional ability revealed that age does not peratures. However, with respect to overall driving perfor- directly influence the performance of commercial drivers, mance, and especially for the more safety-related outcome but exerts a moderate indirect effect through age-related measures, this research, though exploratory, produced changes in perceptual, cognitive, and psychomotor abilities. very encouraging findings. Llaneras et al. (1998) conclude These analyses did reveal significant direct effects on driv- that compensatory and training-oriented interventions can ing performance for (1) psychomotor ability, as measured by accommodate age-related declines in many critical driving range of motion scores; (2) cognitive ability, as measured by abilities. They also suggest that, based on evidence from this accuracy on attention sharing (divided attention) tasks; and work, older commercial drivers may benefit substantially (3) perceptual ability, as measured by depth perception, field from physical therapy to improve range of motion, and that dependence, and useful field of view scores. Within these interventions that improve perceptual ability may enhance functional domains, perceptual ability contributed the most the performance of commercial drivers age 55 and older. to overall driving competence. Prevention: A Case Study Finally, the extent to which four interventions targeted to age-related deficits in these most influential measures of One additional recommendation from the research carried functional ability could enhance driving performance was out by Llaneras et al. (1998) was to develop screening sys- examined. The four interventions included three compensa- tems that incorporate measures of functional ability associ- tory and one training intervention. The compensatory inter- ated with safe driving. Such screening tools--if properly ventions were a prescriptive on-board navigational system validated, easy to administer, standardized, and perceived using auditory commands, an advanced auditory warning to be fair by the drivers who are evaluated--could mark an system that monitors brake system status, and an automatic important step toward the prevention of commercial motor transmission. The training intervention included instruction vehicle crashes. If drivers in the early stages of functional and practice on visual search and scanning techniques keyed loss can be reliably identified, this information might also to the safe execution of turning maneuvers. A treatment make it possible for a larger percentage of aging operators group received all four interventions before driving a test to keep driving safely longer, by taking advantage of the course in the Commercial Truck Driving Simulator, while remediation and accommodation options discussed ear- a matched comparison group relied on a paper map with lier. A case study of an early adopter of driver functional written instructions (identical to the auditory instructions) screening provides an example of how such screening can for navigation, a dummy warning light on the simulator's be implemented. instrument console for warning about an air brake pressure system malfunction, and a nine-speed manual transmission. The subject of this case study is Corry Auto Dealers In addition the comparison group was not exposed to the Exchange (Corry ADE), an auction business in northwest search-and-scanning training. Pennsylvania (Erie County) that employs approximately 75 drivers, some holding a CDL. (This case study descrip- The individual effects of each intervention were assessed tion is based on an April 3, 2009, interview with Tim Swift, on the basis of unique performance variables associated with Vice-President and General Manager of Corry Auto Dealers each countermeasure. For example, the effect of the audi- Exchange. Mr. Swift also became President of the National tory navigation system was assessed in terms of naviga- Independent Automobile Dealers Association in June 2008.) tional errors, adjusting vehicle speed to external conditions, Their workforce, which includes a significant proportion of and adherence to traffic signs and signals; the effect of the drivers age 50 and older, is involved in operations on their auditory warning system was assessed by means of detec- sale lot and in transporting vehicles to and from destinations tion rates for a brake system malfunction; the effect of the around the Northeastern, Mid-Atlantic, and upper Midwest automatic transmission was assessed in terms of variables states. including curve negotiation, executing turns, lane position, fuel management, and brake temperature; and search-and- There is a strong safety culture at Corry ADE. Signs scanning training effectiveness was assessed in terms of emphasizing "Think Safety--It's Everybody's Job" are visual search behavior and mirror checks. Training effec- posted prominently around the premises. Safety videos pro- tiveness also was assessed in terms of several overlapping vided by the National Auto Auction Association are used for measures including executing turns and adherence to traffic driver training. In 2007, at the suggestion of their insurance signs and signals. agent and consultant for risk management, the firm instituted
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20 a routine functional screening program. This screening pleting the screening measures. As a practical matter, facil- program is administered at the time of first hire, then annu- ity with a computer mouse can affect scores on only a single ally, for all drivers regardless of age. measure (visual search); but comfort with test methods helps ensure that (older) drivers do not perceive an age bias when The screening program used by Corry ADE is a com- functional screening is introduced. puter-based version of the test protocol validated against at- fault crashes for drivers age 55 and older in Maryland [see The management of Corry ADE has implemented driver Staplin et al. 2003(b)]. It measures the following functional functional screening (as one component of their safety pro- abilities: high and low contrast visual acuity; head/neck/ gram) for 2 years, and sees a clear value in the information torso flexibility (range of motion); leg strength and mobility; it provides. Analyses relating collisions, either on the lot or visual information processing; visual search (with divided during transport of vehicles to or from other locations, to attention); visualization of missing information; and work- scores on the functional screening battery remain pending, ing memory. These measures are administered by a company however. staff member who was a former safety instructor for the state of Pennsylvania; however, no special training, background, The information provided by functional screening has or credentials are necessary to run the screening program, definite limitations. A poor screening outcome does not which uses onscreen text with accompanying narration to mean that an individual cannot drive safely; but it does indi- present test instructions. cate a priority for follow-up, and a focus for in-depth diag- nostic testing to determine the reason for the functional loss, The screening program requires about half an hour, not and the potential for treatment. Neither does a good screen- counting practice time for drivers who are unfamiliar or ing outcome mean that a driver will not crash; but it provides uncomfortable with using a personal computer. Although some assurance that he or she is not at increased risk of crash- this program can be administered using a touch screen inter- ing owing to functional impairment. With these limitations face, Corry ADE drivers use a mouse to respond to the vari- in mind, the potential benefits of driver functional screening ous functional ability tests. Not surprisingly, older drivers to promote safety and advance risk management in commer- are more likely to need practice with the mouse before com- cial vehicle operations appear substantial.