Model Driver Screening and Evaluation Program
Volume I: Project Summary and Model Program Recommendations


Chapter 2:
Introduction and Background

The preferred personal mobility solution for aging Americans remains the private automobile by a wide and growing margin, as public transit and private transportation services are either unavailable, unaffordable, or unacceptable for reasons of convenience, accessibility, or (perceived lack of) security.1  More than 70 percent of persons age 75+, the fastest growing segment of our population, live in suburbs and small towns that have been designed to accommodate automobile use. Housing areas are typically not close to shops and services, so walking is not often a sufficient mobility solution. In this context, recent projections indicate not only that older persons will dramatically increase in numbers in the U.S., but also that more older people--females as well as males--will retain their licenses and will drive more miles than today' seniors (cf. U.S.DOT, 1997).

What has stimulated this research project is the fact that as we age, albeit in our own unique fashion, we are all at increasingly greater risk of experiencing deficits in the various functional capabilities needed to drive safely. These include the visual abilities needed to detect hazards, while effectively directing attention to critical driving tasks in the face of mounting distractions. Also essential are the perceptual skills needed to accurately judge gaps in traffic, and the cognitive functions necessary to make rapid and appropriate maneuver decisions. Not least are one's physical abilities, including the head and neck flexibility to scan for safety threats before turning, backing, changing lanes, or merging, as well as the arm and leg strength and stamina needed for effective control of the vehicle under normal and emergency response conditions. For virtually everyone in our modern society, to safely operate a motor vehicle demands a higher level of functional ability and functional integration than any other activity of daily living.

Whether a functional deficit results from normal aging, or from diabetes or dementia or any of a number of other diseases that become more prevalent as we grow older, there is reason for serious concern that the result will be driving impairment leading to increased crash risk. Department of Motor Vehicle studies have found that unrestricted drivers with certain medical conditions have significantly higher crash and conviction rates than control groups without impairments (Diller, Cook, Leonard, Reading, Dean, and Vernon, 1999). Given current practices and demographic trends, analysts project a sharp increase in both the number and proportion of traffic fatalities related to the frailties of aging over the first quarter of the 21st century--even to an extent that exceeds alcohol-related fatalities (Burkhardt et al., 1988).

Therefore, as background for this research, it may be asserted that driving while impaired due to functional loss deserves the same recognition as a public health concern, as other types of impaired driving. With the development of recommendations for a Model Driver Screening and Evaluation Program, the National Highway Traffic Safety Administration has set the stage for an injury prevention effort that could have profound and lasting consequences. As its primary focus, the Model Program is designed to keep people driving safely longer, while protecting the public through the identification of functionally impaired drivers. Additional, complementary recommendations designed to help meet seniors' needs to remain independently mobile if they cannot or choose not to continue driving also have emerged as a Model Program priority.

An early and consistent emphasis throughout this project was the need for improved detection of deficits in the functional abilities most important for safe driving. Detection--especially early detection--of functional loss resulting in driving impairments is at least as important to the health and well-being of the older individual who wishes to keep driving, as it is to an agency seeking to fulfill its public safety mandate.

On a population basis, steady declines in visual acuity and contrast sensitivity, in attentional and perceptual processes, in memory and cognition, and in physical strength, flexibility, and range of motion can be very reliably associated with advancing age. But because there are vast individual differences in how people age, chronological age alone is a poor indicator of functional status. While practical considerations may rule out screening at younger ages where deficits are extremely rare, the Model Program assumes a need for direct measurement of key functional abilities, without regard to age per se.

Given this premise, the feasibility of functional capacity screening becomes paramount. Who will perform screening procedures, in which settings, and at what cost? Should drivers be screened regardless of prior history or precipitating conditions, or only if there is evidence of a problem based on crashes or a credible referral for medical review?

Contacts between licensing agencies and older drivers in North America come about principally through the renewal process. The population that would be affected by a broad requirement for screening as a condition of license renewal would vary from one jurisdiction to another, determined by the number of licensed drivers exceeding some age threshold set by the jurisdiction and by the fraction of that number eligible for re-licensure each year according to the prevailing renewal cycle. During Model Program development, this policy was acknowledged as a possibility, but was not promoted explicitly.

Barring mandatory screening, a functionally impaired driver may be detected through direct observation by licensing agency personnel assuming an in-person renewal process--which is promoted, strongly, within the Model Program. Such cases are typically referred for medical determination of fitness-to-drive to a Medical Advisory Board (MAB) or comparable entity within or external to the licensing authority. The MAB also receives referrals from physicians, police and the courts, family and friends, and other sources who are concerned about individuals' abilities to drive safely. Finally, depending on the jurisdiction, a driver may be required to undergo a medical review after accumulating a specified number of crashes or convictions on his/her driving record, or after self-reporting the existence of one or more medical conditions included on a checklist on the license renewal application form.

An essential point is that it is the diminished visual, perceptual-cognitive, and physical abilities themselves, not the underlying medical conditions that may have produced a functional loss, that are of principal concern in determining fitness-to-drive. This has at least two important implications for the Model Program.

First, physicians and other health care professionals who counsel their patients--and may ultimately need to refer them to a DMV--need guidance about the types of driving impairments that are associated with different medical conditions. Recent guidelines issued by the American Medical Association (AMA) Council on Ethical and Judicial Affairs state that "physicians [have] legal and ethical obligations with respect to reporting physical and mental conditions which may impair a patient's ability to drive" (AMA, 1999). The CODES analyses undertaken in different states in collaboration with NHTSA (cf. Diller et al., 1999) have provided valuable data in this regard. Information provided in a literature synthesis performed on behalf of the Association for the Advancement of Automotive Medicine (AAAM) and NHTSA is a major contribution.2 Together these resources have supported development by the AMA of a Guide for Physicians that includes, but is not limited to, a catalog of medical conditions that may impair driving performance.3 In a broader sense, the success of the Model Program similarly rests upon education and outreach--to the general public as well as to health care professionals and other providers of services to seniors--to increase awareness about the relationship between functional capacity and the ability to drive safely.

Second, because of the practical considerations for conducting functional screening on a cost-effective basis, relatively quick and inexpensive procedures will be applied, having certain recognized limitations. Chief among these are levels of sensitivity and specificity that are less than ideal--screening measures are designed to detect gross impairments, and as such are prone to "misses" (impaired drivers who pass the screen) as well as "false alarms" (functionally intact drivers who fail the screen). Obviously, it is important to minimize each of these outcomes; but even more important is to ensure that no restrictions on driving privileges result from screening outcomes alone. Because a functional deficit may be the product of disease or pathology, the proper interpretation of a "failed" screen is that it establishes a priority for further evaluation. A more in-depth, sophisticated, diagnostic procedure may identify a medical condition, previously unknown and untreated, that is amenable to remediation. The Model Program, if implemented, is expected to extend the safe driving years for many individuals when screening initiates events leading to the remediation of functional loss.

Under the Model Program, specific procedures used to screen drivers for gross functional impairments can be expected to share a number of attributes. As already discussed, feasibility of administration is essential, especially if implemented by a licensing agency subject to tight budget controls. Of course, the functional domains targeted by driver screening activities must demonstrate scientific validity as predictors of safety outcomes--crashes, in particular, plus moving violations accepted as common precursors of crashes (e.g., failing to stop at a stop sign). In addition, the abilities measured during driver screening should be perceived by the public to have a clear relationship to driving task demands; in other words, high face validity can increase the acceptance of screening activities by drivers. All of these considerations guided selection of the functional domains and specific screening procedures investigated in this research.

Finally, a Model Program that has the potential to meet the goals set forth earlier must include a component to provide appropriate and constructive feedback to drivers about screening outcomes. Individuals who decline to be tested and voluntarily cease driving, as well as those who score poorly and are referred for additional testing, eventually leading to a restriction or revocation of privileges by the licensing authority, must be not only apprised of but connected to alternative transportation resources in the community. Equally important, individuals who are screened and demonstrate intact functional abilities must be counseled about changes to expect with increasing age, and adjustments in their driving habits that can help to compensate for them. In fact, the functional abilities baseline established through screening with drivers who have yet to experience any significant loss may be one of the greatest benefits of the Model Program.

The Model Program components identified in this introduction--detection of diminished functional abilities, education and outreach efforts, referrals for remediation, and counseling to help older persons remain safely mobile--circumscribe the scope of activities performed in this research project. Early project efforts exhaustively reviewed and summarized technical sources to select a candidate battery of screening measures. Licensing officials were surveyed to gather first-hand information about the feasibility constraints in implementing a driver screening and evaluation program. And the centerpiece of this work, an ambitious pilot implementation of program activities, was undertaken in collaboration with the Maryland Motor Vehicle Admin-istration plus an extraordinary array of partners under the umbrella of the Maryland Research Consortium. This multi-year "study within a study" generated invaluable data to describe cost-benefit relationships, while gauging the scientific merit of the included procedures and producing research products with broad applications to other venues.

This report volume gives a synopsis of each stage of the project, concluding with a general discussion and recommendations for the Model Program supported by present findings. A companion volume details the performance of the Maryland Pilot Older Driver Study.

1Baltimore Region Elderly Activity Patterns and Travel Characteristics Study, 1999. 
Source: Dr. Bonnie M. Dobbs, "Medical Conditions That May Affect Driving." AAAM/NHTSA Consensus Meeting Guidelines, June 2000. 
pers. comm., Dr. Joanne Schwartzberg, Director, Aging & Community Health, AMA, July 29, 2002.