Home Page About Us Contribute

Escort, Inc.

Tweets by @CrittendenAuto

By accessing/using The Crittenden Automotive Library/CarsAndRacingStuff.com, you signify your agreement with the Terms of Use on our Legal Information page. Our Privacy Policy is also available there.

Traffic Tech #219: Medical Conditions And Crash Risk: Do Restrictions On Licenses Have An Impact On Public Safety?

American Government Special Collections Reference Desk

Number 219                                                             April 2000

U.S. Department of Transportation
National Highway Traffic Safety Administration
400 Seventh Street, S.W., Washington, DC 20590


In Utah, there is a special licensing program, developed under the guidance of the Utah Medical Advisory Board, for drivers who have certain medical conditions. The program's guideline describes the physical, mental, and emotional capabilities appropriate for various types of driving, and determines license eligibility by medical condition or functional ability category. The intent was to create the least restrictive program possible that was consistent with public safety. Drivers who are licensed with medical conditions may receive a full unrestricted or restricted license depending on their functional ability level. Restrictions may include speed, area, or time of day limitations. Do drivers with certain medical condition restrictions have more crashes or citations than other drivers?

Utah is one of the seven original states to participate in the Crash Outcome Data Evaluation Systems (CODES) project. Briefly, CODES links crash data describing the details of each crash in the state (generated from the police crash report) with other information like medical and financial information collected at the time of treatment. These data provide information about the nature, cause, and costs of injury resulting from motor vehicle crashes.

Using probabilistic linkage and several different databases, Utah CODES researchers were able to link information on drivers with certain license restrictions to their crash and traffic citation history. The National Highway Traffic Safety Administration (NHTSA) supported the study along with the Utah Driver License Division and the Utah Department of Transportation.

This study evaluated the crash risks of more than 68,770 drivers in the state of Utah who were licensed with medical conditions. Drivers who were licensed with medical conditions were matched to comparison drivers from the general population of drivers, using age, sex, and county of residence as matching factors. The driving records of all of these drivers were used to find the citation, crash, and at-fault crashes for the five years between 1992 and 1996.

Increased Crash Risk

When viewed as a whole, drivers who were licensed with medical conditions had higher risks across crashes, violations, and at-fault crashes than the comparison drivers. Comparisons were not made within medical condition categories because there were often not enough drivers to make comparisons.

Putting It Into Perspective

There were categories in which all drivers, both restricted and unrestricted, showed consistently higher risks for crashes, citations, and at-fault crashes: alcohol and other drugs and vision.

There were also categories where restricted drivers performed better than their unrestricted comparison groups in both crash rates and at-fault crash rates: diabetes and other metabolic conditions; pulmonary conditions; neurological conditions; learning, memory and communication disorders. While the restricted drivers had higher crash rates, they had citation rates similar to their comparison groups. One conclusion is that it might be logical for licensing agencies to consider raising the bar by imposing restrictions at lower levels of functional impairment than is currently the case. Based on crash risk factors, priority categories for evaluating restriction levels include: learning, memory and other communication disorders; psychiatric and other emotional conditions; alcohol and other drugs; and musculoskeletal abnormalities.

These findings will be useful to state licensing authorities in determining appropriate level of restriction for various conditions. Any injury control program must have a multi-faceted evaluation program that is fair to the drivers with medical conditions, and to the interests of safety. In addition, it is unlawful for any State or local government under the Americans with Disabilities Act to discriminate against a qualified person with disability on the basis of those disabilities.


For a copy of Evaluating Drivers Licensed with Medical Conditions in Utah, 1992-1996, (44 pages plus extensive appendices) write to the Office of Research and Traffic Records, NTS-31, NHTSA, 400 Seventh Street, S.W., Washington, DC. 20590, or fax (202) 366-7096. John Eberhard, Ph.D., and Essie Wagner were the contract managers.


Single Functional Ability Category and Comparison Groups with a Single Restriction Status

Condition or Disorder License Status At-Fault Crash Rate Relative At-Fault
Crash Risk
Medical Conditions Comparison Group
Diabetes Not Restricted 1.00 0.69 1.44 *
Restricted 1.10 0.31 3.56
Cardiovascular Not Restricted 0.55 0.55 1.00
Restricted 2.04 1.08 1.88
Pulmonary Not Restricted 0.85 0.68 1.25 *
Restricted 0.43 0.61 0.71
Neurologic Not Restricted 1.26 0.60 2.10 *
Restricted 0.88 0.91 0.96
Epilepsy Not Restricted 1.53 0.82 1.86 *
Restricted 2.22 0.78 2.86 *
Learning, Memory and Communication Not Restricted 2.22 0.82 2.72 *
Restricted 0.00 0.00 zero rate
Psychiatric Not Restricted 1.35 0.71 1.80 *
Restricted 2.70 1.35 2.00
Alcohol and Other Drugs Not Restricted 1.67 0.72 2.33 *
Restricted 7.98 1.30 6.14 *
Vision Not Restricted 1.14 0.75 1.51 *
Restricted 1.19 0.75 1.60 *
Musculoskeletal Not Restricted 1.03 0.54 1.90 *
Restricted 0.00 0.00 zero rate
Functional Motor Not Restricted 1.18 0.66 1.80 *
Restricted 0.00 1.27 zero rate
rate calculated per 10,000 license days.      * statistically significant at the .05 level

U.S. Department
of Transportation
National Highway
Traffic Safety

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

Connect with The Crittenden Automotive Library

The Crittenden Automotive Library at Google+ The Crittenden Automotive Library on Facebook The Crittenden Automotive Library on Instagram The Crittenden Automotive Library at The Internet Archive The Crittenden Automotive Library on Pinterest The Crittenden Automotive Library on Twitter The Crittenden Automotive Library on Tumblr  

The Crittenden Automotive Library

Home Page    About Us    Contribute