Evaluating the crash and citation rates of Utah drivers licensed with medical conditions, 1992–1996☆
Introduction
It is intuitive that medical problems may impair one's ability to safely drive a motor vehicle. Thus, nearly all states have specialized licensing programs for drivers with medical conditions, and most states have specific policies related to physical and mental function and driving (Retchin and Anapolle, 1993). Such programs are intended to improve public safety by controlling the driving privileges of individuals whose driving skills are potentially impaired due to medical conditions. However, there are limited data on driving performance for drivers in such programs (Waller, 1965, Davis et al., 1973, Janke, 1993, Medgyesi and Koch, 1995).
Since 1979, the state of Utah has had a licensing program for drivers who have medical conditions. The program was based upon guidelines written by the Utah Driver License Division Medical Advisory Board, a group of volunteer specialty physicians. Their stated goal was to create a program that improved public safety while imposing the fewest possible restrictions on driving privileges for this group of drivers (Beach, 1992). Since its inception over 20 years ago, the program has had little formal review. We therefore, sought to evaluate Utah's driver licensing program by comparing the rates of adverse driving events (citations, crashes and at-fault crashes) of drivers licensed with medical conditions to those of similar drivers without medical conditions over a 5-year period.
Drivers enter into the program by self-report. Utah's licensing program screens all applicants and renewing drivers with a questionnaire on which they are required to identify any medical problems. (The proportion of drivers with medical conditions who fail to report them is unknown.) Medical condition drivers are then placed into one or more of 12 broad medical diagnosis categories as shown in Table 1 (one of the categories, hearing, is assessed only for commercial drivers and is irrelevant for private drivers and was not included in the study). In each category, drivers are assessed to determine the severity of disease process and impairment; this may require an evaluation by a physician. This assessment of driving ability is used to assign drivers to one of 12 functional ability levels, each signifying various restrictions on driving privileges. Functional ability levels may be broadly categorized as permitting one of three actions: applicants may receive an unrestricted driver's license, a driver's license with restrictions (i.e. driving restricted as to speed, area, and/or time of day) or, finally, be entirely denied driving privileges (level 12). (Levels 1 and 2 are used for commercial drivers only.) Specifics of restrictions for a given functional ability level are not totally consistent between medical conditions, but can roughly be summarized as described in Table 2. The functional ability level and the imposition of restrictions are reconsidered each time the license is renewed. License renewal periods are shortened for all program drivers, at both unrestricted and restricted levels, with renewal periods as short as 3 months. The product of the medical conditions program, then, is the imposition of driving restrictions on drivers who, according to the guidelines, have medical conditions that may impair their ability to drive a motor vehicle.
Section snippets
Methods
This study was approved by the Institutional Review Board of the University of Utah Health Sciences Center and by the Utah Resource for Genetic and Epidemiological Research (for the use of death certificate data).
Information used to perform this study was contained in several statewide databases. Driver license data, specifying dates and types of licensure, renewal dates, and citation data were obtained from the Utah Driver License Division (part of the Utah Department of Public Safety). This
Results
During the study period, there were 1 750 918 Utah licensed drivers; 68 770 (4%) of these drivers were licensed in the medical conditions licensing program. The majority of drivers licensed with medical conditions (54 938, 80%) reported one medical condition, while the remainder (13 832, 20%) reported two or more (Table 3). Of this latter group, the majority (77%, 10 595) was licensed in two categories (Table 3). Drivers in the medical conditions program were older than the general population
Discussion
In this study, we have described the rates of adverse driving events over a 5-year period for participants in a statewide, regulatory licensing program for drivers with medical conditions. We found that: (1) overall, drivers licensed with either single or multiple medical conditions had similar rates of citation but higher rates of crash and at-fault crash than their peers; (2) drivers in the largest medical condition category, ‘cardiovascular’, had rates of adverse events no higher than
Acknowledgements
This study was supported by the National Highway Traffic Safety Administration, Grant number DTNH22-96-H-59017.
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This study was presented, in part, at 26th International Forum on Traffic Records and Highway Information Systems, 7/20/99 Danvers, MA, USA.