Driver Screening and Evaluation Program
Volume I: Project Summary and Model Program Recommendations
The National Highway Traffic Safety Administration (NHTSA) research project, "Model Driver Screening and Evaluation Program," was initiated in 1996, with its ultimate objective to update the guidelines published in association with the American Association for Motor Vehicle Administrators (AAMVA) for screening and evaluating medical fitness to drive. This research was undertaken as a proactive response to the unprecedented number and proportion of older persons who will make up the driving population of the early 21st century, and the mounting evidence that age-related declines in the functional abilities needed to safely operate a motor vehicle, under everyday traffic conditions, result in significantly greater odds of causing a crash. The consequent increases in injuries and fatalities that will be experienced by our nation's seniors (and by others who share the highways with them) are expected to define a major public health concern, demanding innovative policies and practices to reduce the incidence of "driving while functionally impaired" while extending the benefits of safe mobility to our oldest citizens.
Early project activities were directed to identifying: (1) functional limitations resulting from normal aging, and from diseases and pathologies that are more prevalent with advancing age, that impair safe driving; and (2) currently-available test procedures that offer the highest validity to detect functional loss and that can be feasibly administered by licensing agencies. These goals were met in part through a comprehensive review and synthesis of technical information that culminated in the Annotated Research Compendium of Age-Related Functional Impairments and Driving Safety and the Safe Mobility for Older People Notebook. These research products may be accessed online at www.nhtsa.dot.gov/people/injury/olddrive/safe/.
Additional guidance in meeting the initial project goals was received from a Delphi panel of experts in relevant fields of medicine and driving rehabilitation. The list of specific sensory (visual) functions, attentional-perceptual processes, and medical factors (including dementia) that are most critical to safe driving was narrowed through the panel's input, then was sorted to reveal the most significant gaps in the existing state-of-the-knowledge. These gaps defined priorities for the pilot tests planned later in the project, in terms of domains of functional ability, and suggested specific measurement procedures that could be applied within those domains.
Next, a clear understanding of the possible barriers to implementing a driver screening and evaluation program--especially as seen from the perspective of State and Provincial Driver License Administrators--was needed, to preclude a set of research findings with scientific merit but no practical value to those who would ultimately be charged with carrying out a majority of Model Program recommendations. With the support of AAMVA, a survey was distributed and responses received from 58 of the 62 licensing jurisdictions in North America that identified the legal, policy and cost implications of screening as contemplated under the Model Program.
With the information gained thus far, the design for the Maryland Pilot Older Driver Study proceeded. This effort, accounting for by far the largest expenditure of project resources, was a collaboration between the NHTSA research team, the Maryland Motor Vehicle Admin-istration (MVA) and its Medical Advisory Board (MAB), and a group of additional partners from Government, universities, non-profit organizations, and the private sector collectively identified as the Maryland Research Consortium (MRC). With guidance from the MRC, the MAB implemented a battery of functional screening measures in MVA field offices and in community settings, using specially-trained agency staff to administer and score the test procedures and obtain driving habits information from the study samples for later analysis by the research team. Functional screening data were collected and analyzed for three distinct samples of drivers age 55 and older--a population-based sample of 1,876 drivers, who visited field offices for license renewal or other transactions; 366 drivers referred by various sources to the MVA for medical evaluation because of suspected driving impairments; and 266 drivers in a suburban, residential community for seniors who used the services of a mobile MVA office that made periodic visits to their facility.
Analyses of Pilot Study data focused on the relationships between the measures of functional ability in the screening battery and a range of traffic safety outcome measures. The safety outcomes were three categories of crashes (all crashes, at-fault plus unknown-fault crashes, and at-fault crashes only) plus three categories of moving violations (all moving violations, all moving violations except speeding, and all moving violations except speeding and occupant restraint violations). Outcomes measures were tabulated from Maryland State Highway Administration (SHA) databases for each study participant, keyed to individuals' dates of testing. All events in a period of time bracketing the functional screening date for a driver by one year prior, and (on average) two years after the test date, were eligible for analysis. Odds ratios (OR) were calculated for each screening measure investigated in the Pilot Study; by expressing the odds of experiencing a crash or moving violation if a driver fails a given test versus the odds if he or she passes the test, this analysis technique can provide an index of the predictive value of measuring changes in a driver's functional status.
The Pilot Study results provided strong evidence that functional capacity screening, conducted quickly and efficiently in office settings, can yield scientifically valid predictions about the risk of driving impairment. Four domains of perceptual-cognitive ability were high-lighted: 1) directed visual search, 2) information processing speed for divided attention tasks, 3) the ability to visualize missing information in an image, and 4) working memory. Two physical functions also emerged as measurement priorities: 1) lower limb strength, and 2) head/neck mobility (rotation). It may be noted that visual abilities, which are already assessed as part of the licensing process, were not addressed in the Pilot Study data collection activities. Cost analyses, based on MAB experience, support cost-per-driver-screened projections of $5 or less.
At a finer level, the Maryland Pilot Study confirmed that certain, specific procedures have utility for performing functional screening and, in some cases, identified candidate cutpoints for pass-fail determinations using those procedures. Model Program recommendations from this research remain focused on the domains of functional ability that should be targeted by screening activities, however. In the anticipation that future work will contribute data verifying the obtained predictor-criterion relationships, and the promise of new and more cost-effective testing methods--included automated testing--than were available at the initiation of the Pilot Study, interested parties are encouraged to contact a NHTSA program officer in this area for guidance about the most current options for implementing functional capacity screening.
In a broader sense, this research reinforces the notion that functional screening to assure the "driving health" of older persons is rightfully viewed in the context of injury prevention. As such, its potential benefits to individuals and to society are profound, if integrated with education and counseling to improve awareness about the risks associated with functional loss, referrals for remediation of functional loss whenever possible, and connection to alternative transportation resources to preserve--instead of penalizing--the independent mobility of affected drivers.
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