North Carolina's medical evaluation of drivers is directed at identifying those drivers believed to have physical and/or mental problems that might adversely affect their driving. When an individual is believed to have a medical impairment, he is required to have his physician complete a Medical Report Form. This form is scrutinized by the Medical Advisor, a medical disability code(s) assigned, and a decision is made to grant, restrict, prohibit, or withdraw the individual's driving privilege.

In order to examine the influence of the medical review on driver performance, as measured by the number of violations and accidents, two groups of persons were selected from the North Carolina Medical Evaluation file - those with a primary disability code of cardiovascular disorder (N = 7,462) and those with a code of epilepsy/seizure (N = 1833). The driving record of each subject was then examined for a period of time immediately preceding and following the date of the subject's first medical evaluation.

In order to compare the performance of these subjects with that of the general N.C. driving population, a matched control group was selected as follows. For each subject in the medically impaired groups three control drivers not having any medical restrictions were selected who matched the subject with regard to age, race, and sex. The driving records of the control subjects were examined over exactly the same time periods as their matching counterparts in the medically impaired groups.

Comparisons of the distributions of accidents and violations were made between the medical and control groups in both time periods and with respect to their change over time. Comparisons were also made for various subgroups determined by type of medical restriction.