Driver Screening and Evaluation Program
Volume I: Project Summary and Model Program Recommendations
The underlying premise for this research is that driving while impaired due to declining functional abilities defines an emerging public health priority. This is borne out by the surge in population of our nation's oldest citizens, their continuing reliance on private automobiles to meet essential transportation needs, and--as underscored by the present findings--the increasing odds of serious violations and crashes associated with the loss of functional abilities that decline with advancing age. In response, this project has investigated the validity and administrative feasibility of specific practices designed to promote safe mobility for older people and all people in the U.S. Project results support recommendations for an integrated set of functional testing, education, counseling, and referral-and-remediation activities collectively labeled the NHTSA "Model Driver Screening and Evaluation Program."
A starting point is the education/outreach component of the Model Program. There is a universal need for improved awareness of the relationship between functional decline and the risk of injury to older drivers themselves. With greater involvement in serious violations and crashes, and a higher vulnerability to injury and death due to their frailty, older drivers and their families are a primary audience for safety materials explaining why it is important to detect changes in specific functional abilities, how to self-test these abilities, and what can be done to adjust one's driving habits to compensate for functional loss. The "How Is Your Driving Health?" brochure developed as a product of this research (see appendix C) may be recommended for distribution in public and private sector settings, including Senior Centers and other social service settings visited by older persons and/or their adult children. This brochure can also be used to complement the exemplary community outreach activities in this area already initiated in certain jurisdictions around the country.1
Education and outreach activities directed to physicians, occupational therapists, and other professionals in the health care community are also critical. Older persons, when asked who they trust the most to give them advice about fitness to drive, and whose advice to restrict or cease driving they would most likely heed, typically name their personal physician. In addition, physicians have been sensitized to issues relating to medical fitness-to-drive due to changes in States' reporting laws or in the enforcement of those laws in some jurisdictions,2 as well as new guidance from the American Medical Association in this area.3 But, in many cases these professionals require a better understanding of the driving impairments resulting from functional loss associated with specific medical conditions; also, they may find that the screening tools examined in this research are useful in helping to assess their older patients' fitness-to-drive.
The results of the Maryland Pilot Older Driver Study have been offered as evidence that functional capacity screening to detect deficits in the abilities most important for safe driving can be performed, practically and reliably, in a variety of (office) environments. Granting the use of automated testing procedures to acquire the screening data, wherever possible, a cost-per-driver at or below five dollars ($5) including administrative and support services may be projected with confidence. The Pilot Study analyses, building on the earlier synthesis of technical information documented in the Annotated Research Compendium, have targeted the domains of visual, mental, and physical ability shown in table 3 as measurement priorities in a screening program. The approximate duration of testing is also noted in this table.
|Targeted Functional Ability||Test Method and Duration of Testing|
|1. Visual Acuity (Near and Far)||Manual Test Administration: 1 minute
Automated Test Equipment: 1 minute
|2. Visual Contrast Sensitivity||Manual Test Administration: 1 minute
Automated Test Equipment: 1 minute
|3. Field of View||Automated Test Equipment: 1 minute|
|4. Working Memory||Manual Test Administration: 1 minute|
|5. Directed Visual Search||Manual Test Administration: 6 minutes
Automated Test Equipment: 3 minutes
|6. Visual (Divided) Attention Processing Speed||Automated Test Equipment: 4 minutes|
|7. Visualization of Missing Information||Manual Test Administration: 3 minutes
Automated Test Equipment: 3 minutes
|8. Lower Limb Strength and Mobility||Manual Test Administration: < 1 minute|
|9. Head-Neck Rotation||Manual Test Administration: > 1 minute|
Recommended vision tests include the measurement of (1) near and far acuity and (2) contrast sensitivity, and testing for (3) visual field loss. These visual functions help determine how well and under what conditions a person can sense objects in the roadway environment. As performance in visual function declines, the probability that hazards, traffic control messages, navigational cues and other safety-critical information will be detected early enough so that a driver can understand and apply the information to maneuver safely falls to an unacceptably low level.
Both manual and automated techniques that are effective for performing acuity and contrast sensitivity testing are commercially available. In the latter case, both standalone testing machines and computer-based testing programs are available; respectively, these require proper maintenance and careful adherence to instructions regarding viewing distance and control over ambient lighting conditions. These same concerns also apply with manual techniques (e.g., wall charts). Testing for limitations in visual field size is more difficult. Manual (sometimes called "confrontational") techniques are notoriously unreliable. While vendors of standalone vision testing machines commonly advertise this measurement capability, a clinical (ophthalmological) perimetry evaluation is most reliable.
Recommended tests of mental functions include the measurement of (1) working memory plus (2) visual (divided) attention processing speed, (3) directed visual search, and (4) the ability to visualize missing information. These capabilities enable motorists to seek and acquire infor-mation needed for everyday driving, to recognize and anticipate safety threats, and to make timely and appropriate maneuver decisions to avoid hazards and conflicts with other road users.
The measurement of working memory, of directed visual search, and of a person's ability to visualize missing information can all be accomplished using manual methods drawn from neuropsychological test batteries. Automated (computer-based) methods are also available, as used in the Maryland Pilot Study. Obtaining manual measures of how fast a driver can divide and switch his or her attention is problematic, however. Because response times are measured in fractions of a second, only computer-based testing of this ability is feasible.
Recommended tests of physical ability include tests of drivers' (1) lower limb strength and mobility and (2) their head-neck rotation capability. Measures of the former ability predict how quickly a driver can move his or her foot from the accelerator to the brake in an emergency situation, while the latter ability influences how well the driver can scan the environment for conflicts, especially at intersections and when merging or changing lanes.
The Summary and Conclusions chapter in Volume 2 of this report emphasizes that the present research findings, while highlighting the most important domains of functional ability to measure in a driver screening program, leaves open the question of the "best" measurement techniques. The procedures described in Volume 2 were selected based on practical as well as scientific considerations; while the specific screening techniques applied in the Pilot Study are represented here as effective options to accomplish the recommended measures of functional status, they are not represented as the only options. This is an active area of research and development, where it is more likely a question of "when" than "if" more cost-effective testing methods become available. It is recommended that interested readers contact NHTSA staff in this program area to learn about currently available measurement options.
Regardless of the specific method(s) applied to determine a driver's functional status, the role of screening as envisioned in the Model Program remains constant: Screening outcomes serve as a trigger for other educational, counseling, referral, or diagnostic evaluation activities, not as grounds, in themselves, for any licensing decision or action.
Based on the interpretation of broad trends in the screening data analysis results from the Maryland Pilot Study (see Volume 2), the results of screening procedures should be used to assign a driver to a low versus a high priority for further evaluation. This assignment, in turn, will reflect two different performance thresholds or "cutpoints" for each measure of functional ability included in a screening battery. These respective cutpoints connote an emphasis on prevention versus intervention activities at different levels of functional loss, as diagrammed in figure 2.
Within this framework, individuals who score above (i.e., those who perform better than) the "prevention threshold" on all functional measures in the screening battery effectively receive a clean bill of health. For these persons, a functional performance baseline will be established against which future decline may be monitored. This may be accomplished through screening by a licensing agency as part of the renewal process; through testing by others, in particular physicians and other health care providers; or by self-testing. Educational materials should be provided to these intact, healthy individuals to underscore the importance of early detection of functional loss.
In the Model Program, individuals who score below the "prevention threshold" on one or more functional measures in the driver screening battery would receive further evaluation. It is assumed that these evaluations would either be performed by a licensing agency, or by others acting in accordance with procedural guidelines and requirements established by a licensing agency. The nature and the urgency of such evaluations would depend upon how far below this threshold a driver scores. If an individual scores below the "prevention threshold" but above a second cutpoint connoting an "intervention threshold," he or she has the lowest priority for further evaluation. It is at this point that the opportunities for remediation or to make changes in driving habits to keep driving safely longer are greatest.
Individuals having the highest priority for further evaluation are those who not only score below the "prevention threshold," but also fail to perform at or above the lower cutpoint, or "intervention threshold." This cutpoint connotes a more advanced stage of decline on one or more functional measures, where immediate diagnostic testing is necessary for the protection of both the individual and the general public, and the risk of driving impairment is high.
Establishing the cutpoint scores identifying a "prevention threshold" and an "intervention threshold" is obviously a key aspect of any driver screening program. These scores should reflect analyses of very large, population-based samples that provide an accurate understanding of (a) how functional abilities change with normal aging, and (b) the extent to which functional decline can be related to motor vehicle crash involvement, in particular "at fault" crash involve-ment. The analyses performed and the [MaryPODS] database developed in the Pilot Study represent an important step in this process; but, they must be augmented with more data--ideally including analyses based on longitudinal study of functional status predictors versus safety outcome criteria--before a more definitive assignment of cutpoints will be permitted. In the interim, candidate cutpoint values for the specific screening measures investigated in the Pilot Study can be found in Volume 2. As before, it is recommended that interested readers consult a NHTSA program officer with responsibilities in this area, to get an update about the current state-of-the-knowledge.
To adhere to a core objective in the Model Program to keep people driving safely longer, the prospect of functional capacity screening with a potential for subsequent diagnostic assess-ment should lead, as often as possible, to adaptive or remedial strategies. In this regard, the availability of counseling services to help explain test results and answer drivers' questions about what to do next is a necessary accompaniment to functional screening, wherever it is performed.
In the Pilot Study, counseling services, employing occupational therapists, were provided only for the sample of drivers screened at Leisure World--although this was a central element planned for the program activities introduced briefly but then discontinued at the Howard County Area Agency on Aging (Senior Centers). The cost-benefit relationships considered in this report posit counseling for at least a subset of individuals who are impaired with respect to one or more safe driving abilities. These individuals need some appraisal--even when further evaluation is pending--of whether continued driving, albeit with restrictions, is an option. If so, the nature of the restrictions the DMV might impose, and their impact on the driver's mobility and quality of life should be discussed. If continued driving depends upon remediation of a functional deficit, the nature and amount of time required to complete the remediation, its eligibility for coverage under Medicare or other insurance, and its prospects of restoring full or partial driving privileges should be addressed empathetically but realistically. A useful resource in these subject areas is provided by the Safe Mobility for Older Persons Notebook completed in this project.
Counseling is most critical for persons determined through screening and assessment activities to be at too high a risk of impairment to continue driving, and for whom there is no realistic potential for remediation of functional deficits. These individuals must be "connected" to alternative transportation options in the community. Alternative transportation provides the "safety net" that allows individuals who cannot or choose not to continue driving to maintain the dignity and quality of life afforded by independent mobility. It may be noted that in the vast majority of cases an older person who ceases driving will not choose to use a publicly-funded alternative transportation option, whether fixed-route or demand-responsive (e.g., paratransit). Connecting persons in need of alternative transportation to appropriate providers thus begins with accurate and up-to-date information describing public and private options, the names and numbers of contact persons, hours of service, fees, and restrictions, if any, on the availability and nature of service. For example, door-to-door services must be distinguished from curb-to-curb services. Though outside the scope of the present research, the need under the Model Program to acquire and regularly update such information on a city, county, and regional basis cannot be emphasized too strongly.
Perhaps most daunting is the challenge of translating the various program components identified in this chapter into a real-world application; to move from an abstract, disassociated discussion of recommended practices to a fully-integrated infrastructure of people and processes sufficient to accomplish the stated goals of the Model Program. For practical purposes, it must be assumed that a significant number, if not all, of the functional screening, education and counseling, and referral-for-remediation components referenced herein will fall under the purview of a motor vehicle administration or DMV. Following the experience of the Pilot Study, it will be further assumed that a Medical Advisory Board or similar entity in a given jurisdiction will be the key organizational unit for coordinating and carrying out driver screening and evaluation program activities.
Within that context, a framework for evaluating a person's medical fitness to drive is shown in figure 3. This model closely parallels the operations that have been put in place in the State of Maryland, in large part as the result of this research. Certainly we recognize that each jurisdiction engaged in driver screening and evaluation activities will face different challenges in delivering services that are both cost-effective and acceptable to the public, and will develop somewhat different solutions. At the same time, lessons learned in the Maryland Pilot Study suggest a general framework for program organization and flow of program operations that should broadly benefit all jurisdictions in meeting common safety and mobility goals. These lessons learned are embodied in a pending publication, Model Driver Screening and Evaluation Program: Guidelines for Motor Vehicle Administrators (NHTSA, 2002).
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