Maria T. Schultheis, PhD , Elizabeth Whipple, PhD
Driving is a complex task that requires the successful integration of perceptual, physical, cognitive, and emotional systems. Individuals with brain injury (BI), along with their families and care providers, are often faced with the determination about an individual’s capacity to return to driving post-BI. This brief report offers a synopsis of primary areas of assessment relevant to determining driving capacity following BI.
Relevant Factors of Driving Capacity
To date, there is no one unified and standardized and accepted clinical driving evaluation process. This is further complicated by the lack of federal guidelines and/or mandates to provide overarching directions to clinicians charged with the task of determining capacity to returning to driving post-BI. Therefore, clinicians (which can include physicians, occupational therapists, physical therapist and neuropsychologists) often rely on the assessment of various factors that have been identified as relevant to driving. Across the literature, the areas consistently identified include vision, motor/physical and cognitive performance.
Vision
• Although vision is the primary sensory related to safe driving and is the only sensory domain evaluated legally, there is a dearth of studies that have examined it specifically following BI.
• Existing legal visual requirements primarily focus on visual acuity (i.e., 20/20, or the ability to resolve detail at 20 feet), but these requirements are highly variable from state to state (see American Association of Motor Vehicle Administrators)
• Visual field is the second most commonly evaluated visual ability in relation to driving, and like acuity, the requirements for visual field vary on a state-by-state basis. Unlike visual acuity, which has clear metrics, the definition of visual field differs across studies (Owsley, C. & McGwin, 2010)
• Conflicting findings result from these murky operational definitions. Taken together findings from this research suggest that individuals with visual field impairments may be compromised on some aspects of driving performance (e.g., identification of signage) but unaffected in other areas (e.g., speed estimation).
• Studies with other neurological populations have demonstrated that other visual domains warrant consideration when determining driving risk (Schultheis et al, 2010), for example contrast sensitivity and visual processing speed. In older drivers, impaired contrast sensitivity is associated with a recent history of crash involvement and with driving modification and difficulty (Owsley et al 2010). Similarly, in older drivers slowed visual processing speed and visual inattention have been linked to number of crashes (Owsley et al 1998) and problems with vehicle control (wood et al, 2009).
Conclusion: Overall, driving is a highly complex visual task, and each aspect of visual functioning must work within an integrated system in order to successfully navigate the driving environment. Therefore, it is recommended that the standard visual acuity test be supplemented with other assessments of visual functioning (e.g., contrast sensitivity, visual field, processing speed, and divided attention).
Motor
Physical domains, including strength, coordination, grip, and reflexes in both the upper and lower extremities are basic requirements for managing automobile control devices (e.g., steering wheel, pedals).
Following BI, these motor skills may be compromised due to residual difficulties with weakness, hemi-paralysis, ataxia or rigidity.
• Physical fitness should be evaluated in clinic prior to on-the road assessment.
• Physical assessment should include range of motion, muscle tone, strength and endurance, coordination, balance, proprioception and mobility.
• Even minor impairments in a person’s ability to integrate information from the sensory, motor programming, and muscular-skeletal systems can lead to significant disability.
• While motor and physical capacity is commonly evaluated by physical therapists, many driver specialists commonly incorporate gross motor measures of upper and lower extremity to determine the need for adaptive driving equipment
Cognition
The majority of existing literature on driving post-BI has focused on defining the relationship between cognitive impairment and driving performance. In general, the main areas of cognition identified as relevant are consistent with findings from other neurologically compromised populations
• Deficits in selective and divided attention, memory, and information processing speed all negatively impact driving safety (Ortoleva et al 2012).
• Attentional impairments are particularly concerning in an on-road environment, as BI survivors are often easily distracted, unable to recognize hazards, or unable to multi-task successfully.
•Similarly, a slower processing speed means a slower reaction time, slower driving, and slower decision-making.
• Executive functioning impairments, particularly in the areas of inhibition, planning, abstract reasoning skills, and selfawareness, can also affect driving performance (Ortoleva et al 2012). As judgment and insight are can be impaired
after BI, drivers may be prone to more risk-taking behaviors, demonstrate poor awareness of driving problems or accidents, or be unable to recognize driving errors.
• However, patients with mild to moderate deficits who appreciate their own cognitive limitations have been found to pass an on-the-road evaluation more successfully than patients with a similar neuropsychological profile who also display anosognosia (Schanke et al, 2000)
An important consideration, regarding cognition is the varying utility of formal cognitive testing dependent on the level of cognitive compromise. For example, cognitive testing maybe useful for detecting severe deficits in clients who may be unsafe behind the wheel prior to an on the road assessment and thereby help ensure the safety of both the driver and the evaluator. By contrast, the relationship between mild cognitive impairment and driving performance is less defined.
Unfortunately, to date there is limited empirical evidence to inform the specific cognitive aspects of driving and the consistency of predictive validity of these tests. However, integrating findings from across the various neurological populations has yielded some robust findings, including the identification of key cognitive domains. (see TABLE 1 for summary).
Summary: Although neuropsychological testing alone is not sufficient to predict driving fitness, it can discriminate among groups with differing skill levels and provide useful information to supplement an on-the-road test. However, caution is warranted regarding generalization, as some studies have found that around 60% of patients with neuropsychological scores that suggest driving difficulties are deemed to be safe drivers following an on-road assessment (Schanke et al 2000).
Other Factors
Other factors to be considered in an assessment of driving capacity include the patient’s premorbid driving history, as personality and risk-taking behaviors pre-injury may have implications for driving safety post-recovery. Lowered self-awareness and lack of insight into deficits is often a symptom of BI, however, some studies have found that drivers with BI are capable of recognizing changes in their driving skills, and often self-limit their own driving (i.e., avoid driving at rush hour or at night). Finally, other consequences of BI such as fatigue, the inability to appreciate consequences, and emotional lability (e.g., impulsivity, anxiety, irritability, apathy) may also lead to dangerous situations on the road (Bivono et al, 2012).
Finally, an important consideration that is commonly overlooked or not addressed clinically is the need for repeated driving evaluations. Unlike the legal process, which requires some aspect of licensure renewal for all drivers, among clinical populations, a formal driving evaluation process is typically seen as a one-time requirement. More specifically, the driver evaluation focuses on the readiness of the individuals to pass the legal driver examination. This is because clinical driver specialists do not have the authority to approve or decline legal driving status. Given this, after most individuals have received and passed a clinical driving evaluation, they go on to receive their state licensure.
This license is then subject only to required legal renewals– that are typically minimal and do not take medical aspects into consideration. What is most concerning about this process is the compiling evidence that the sequelae of BI can change over time and with the aging process32. BI residual symptoms may be experienced years after the injury, and can include a variety of difficulties (e.g., daytime sleepiness; fatigue; risk of seizures; cognitive, motor, and sensory deficits) (Brenner et al, 2008). More importantly, the aging process likely compounds these symptoms. As a result, aging adults with a positive history of BI may be at higher risk of driving accidents than their aging cohort (Brenner et al, 2008).
Conclusions: Taken together, the determination of the ability to return to driving post-TBI is best supported by a multi-level, multidomain evaluation. Clinicians should incorporate the expertise of vision, physical/motor, cognition and driver rehabilitation specialists.
Resources
American Congress of Rehabilitation Medicine-Brain Injury Long Term Issues Task Force. Brain injury, aging, and health: Conducting large scale survey research. Rehabil. Outlook 8, (2001).
Association of Driver Rehabilitation Specialists: www.aded.net
American Medical Association: Clinician’s Guide to Assessing and Counseling older Drivers: https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/812228_cliniciansguidetoolderdrivers.pdf
Schultheis, M. T., DeLuca, J., & Chute, D. (Eds.). (2011). Handbook for the assessment of driving capacityAcademic Press.
References
Brenner, L. A., Homaifar, B. Y. & Schultheis, M. T. Driving, aging, and traumatic brain injury: Integrating findings from the literature. Rehabil. Psychol. 53, 18–27 (2008)
Bivona, U. et al. Return to Driving After Severe Traumatic Brain Injury: Increased Risk of Traffic Accidents andPersonal Responsibility. J. Head Trauma Rehabil. 27, 210–215 (2012).
Ortoleva, C., Brugger, C., Van der Linden, M. & Walder, B. Prediction of Driving Capacity After Traumatic Brain Injury: A Systematic Review. J. Head Trauma Rehabil. July 27, 302–313 (2012)
Owsley, C. & McGwin Jr., G. Vision and driving. Vision Res. 50, 2348–2361 (2010).
Owsley C, Ball K, McGwin, Jr G & et al. VIsual processing impairment and risk of motor vehicle crash among older adults. JAMA 279, 1083–1088 (1998).
Schultheis, M. T. et al. Vision and Driving in Multiple Sclerosis. Arch. Phys. Med. Rehabil. 91, 315–317 (2010).
Schanke, A. K. & Sundet, K. Comprehensive Driving Assessment: Neuropsychological Testing and On-road Evaluation of Brain Injured Patients. Scand. J. Psychol. 41, 113–121 (2000).
Wood, J. M. et al. On-Road Driving Performance by Persons with Hemianopia and Quadrantanopia. Invest. Ophthalmol. Vis. Sci. 50, 577–585 (2009)
Author Bios
Maria T. Schultheis, PhD, is the Vice Provost of Research, within the Office of Research and Innovation at Drexel University in Philadelphia, PA. Dr. Schultheis is a tenured full professor in the Department of Psychology and she is a Clinical Neuropsychologist who received her PhD in Clinical Psychology in 1998. Dr. Schulthies’ clinical and research experience have been focused on the rehabilitation of cognitively impaired populations, including traumatic brain injury, stroke and multiple sclerosis.
Navy Lt. (Dr.) Elizabeth Whipple was commissioned as a lieutenant in the fourth year of her Ph.D. program in clinical psychology at Drexel University. She completed her internship at Naval Medical Center San Diego in 2017 and completed her first tour at US Naval Hospital Guam. She currently serves as an embedded psychologist with Naval Special Warfare Command in Coronado, CA. Dr. Whipple’s research interests include TBI, combat stress, and driving behaviors of post-9/11 combat veterans.