Traffic Tech #244: Evaluating Drivers Licensed With Medical Conditions In Utah, 1992-1996 |
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Utah is one of the initial seven states that implemented the Crash Outcome Data Evaluation System (CODES). CODES links computerized data from motor vehicle crashes with those from several health care related data sets including emergency medical services and hospital inpatient and emergency department databases. Drivers are first categorized by their specific medical conditions at the time of license application or renewal. Drivers who are licensed with medical conditions may receive a full unrestricted or restricted license depending on their functional ability level.
In January 2000, the National Highway Traffic Safety Administration (NHTSA) published the first in a series of reports evaluating licensed drivers who have medical conditions (see Traffic Tech 219). This second study extended the analyses to examine each medical condition (or functional ability category) by up to 12 functional ability levels for each condition. It also included drivers with multiple medical conditions. The Utah Driver License Division's program guidelines describe the physical, mental, and emotional capabilities appropriate for various types of driving and thus determine license eligibility. Restrictions on licenses may include speed, area, and time of day limitations.
The study compared the citation, total crash, and at-fault crash rates of 68,770 drivers licensed with medical conditions with the rates of similar drivers matched on age group, gender, and county of residence. Comparison drivers were obtained randomly from the general driving populations. Rates of adverse driving events were examined over a five-year period, 1992-1996.
The 12 Functional Ability Levels and Driving Risk or Limitations:
1-2 Irrelevant for private drivers. 1 is used for commercial drivers and 2 is for drivers with a history of a medical problem which is now resolved. No restrictions on driving privileges or licensing periods.
3-5 No restrictions on driving privileges: licensing periods are shortened
6 Driving with speed limitations
7 Driving with speed and area limitations
8 Driving with speed, area, and time of day limitations
9 Driving accompanied by a licensed driver with limitations of speed and/or area and/or time of day limitations as recommended by health care professional
10 Special driving limitations recommended by health care professional not covered above
11 Under evaluation -- may or may not drive, according to circumstances as determined by director, with medical advise as appropriate
12 No driving
Approximately 80 percent (54,825) of the drivers who reported a medical condition reported a single medical condition. When these drivers were analyzed for adverse driving events by specific medical condition and functional ability level, some patterns emerged. The overall rate of citations for drivers with medical conditions did not differ in any consistent way from that of comparison drivers. The crash and at-fault crash rates for drivers with most medical conditions, however, were significantly higher than comparison group rates for at least some functional ability levels. These differences were found at functional ability levels where driving privileges were not restricted. Medical conditions showing significantly higher rates of citations included psychiatric conditions and visual acuity, levels 3-5. All medical conditions, except cardiovascular, showed significantly higher rates for crashes and at-fault crashes, for ability levels 3-5, depending on the specific conditions.
Approximately 20 percent (13,408) of the drivers with medical conditions were in more than one category. Most (10,595) reported two medical conditions, although combinations of as many as seven occurred.
Higher rates of crashes and at-fault crashes, compared to comparison drivers were found for drivers with the following combinations of medical condition:
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Unrestricted Drivers |
Restricted Drivers diabetes & cardiovascular neurological & musculoskeletal neurological & functional motor musculoskeletal & functional motor cardiovascular & visual acuity (at fault crashes only) |
The authors note two additional limitations. First, accurate measurements of exposure (miles driven) and other factors that affect the risk of citation or crash are not available. In the absence of exposure data, the comparison drivers were selected by age group, sex, and county of residence. Other factors, however, such as marital and economic status, employment, educational status, being a member of a social or religious organization, and residential demographics, could also influence the amount people drive and their exposure level. The second limitation is that this medical conditions program relies on self-reporting through a general questionnaire administered by the Utah Driver License Division. There is a disincentive for applicants to report a medical condition, since doing so may require a longer wait for a driver's license or a visit to a health care professional, or both.
Conclusions
The authors suggest that the 12 functional ability levels available for each medical condition could be simplified for evaluation to reduce small cell sizes in some conditions, and to better evaluate drivers who have multiple conditions. Under the current system, it is possible for a driver with multiple conditions to have several license restrictions or licensing periods. They also conclude that changing the restriction line is not warranted based on these data. More research is needed, particularly in obtaining exposure data on drivers with different levels of restrictions. Until more definitive results are found, these are important factors for the Utah Driver License Division, the Utah Medical Advisory Board, and any other policymakers to consider before implementing any policy changes. They must also consider that it is unlawful for any State or local government under the Americans with Disabilities Act to discriminate against a qualified person with a disability on the basis of those disabilities.
HOW TO ORDER
For a copy of Further Analysis of Drivers Licensed with Medical Conditions in Utah (44 pages), write to the Office of Research and Traffic Records, NHTSA, NTS-31, 400 Seventh Street, S.W., Washington, DC 20590, or fax (202) 366-7096. Essie Wagner was the contract manager.
U.S. Department of Transportation
National Highway Traffic Safety Administration
400 Seventh Street, S.W. NTS-31
Washington, DC 20590
Traffic Tech is a publication to disseminate information about traffic safety programs, including evaluations, innovative programs, and new publications. Feel free to copy it as you wish.
If you would like to receive a copy contact:
Linda Cosgrove, Ph.D., Editor, Evaluation Staff
Traffic Safety Programs
(202) 366-2759, fax (202) 366-7096
E-MAIL: lcosgrove@nhtsa.dot.gov