Elderly drivers have 7 percent fewer traffic fatalities in states where drivers are required to pass vision tests before they can renew their licenses, a new study has found.
And the more frequently drivers are tested, the more the fatality rates fall.
However, some states have been increasing the intervals between license renewals to save money. Maryland's was extended from four years to five in 1992.
"In the short run, you can save money by having less frequent renewal. But in the long run, people die," said Dr. David T. Levy. He is a professor of economics at the University of Baltimore's Merrick School of Business and principal investigator in the study.
The study, by researchers at UB and at the Johns Hopkins School of Hygiene and Public Health, was reported today in the Journal of the American Medical Association. It was funded by the Centers for Disease Control and Prevention.
"A state that does not have vision testing at license renewal, after reading this study, ought to very strongly consider adding such a policy," said Jon S. Vernick, a co-author of the study and a research associate at the School of Public Health.
The benefits of vision tests for older drivers have been noted before. But this is the first study with a national scope and the first to control other factors that might influence the risk of fatal crashes, such as average highway speeds, the volume of trucks, the availability of hospitals and the degree of urbanization.
The elderly drive less than younger people and are less likely to be involved in fatal crashes. But when they are on the road, drivers over age 65 experience higher rates of fatal accidents per mile driven than any group except teens.
Experts blame their declining visual acuity, narrowing field of vision and difficulty with night vision.
The elderly have particular problems turning left at intersections with oncoming traffic.
The dangers will grow as the number of elderly drivers increases from 13 million today to 30 million by 2020.
At the same time, the study's authors acknowledge that more restrictive licensing policies have costs, including reduced mobility for the elderly. They urged further study.
The study examined fatal crashes from 1985 through 1989 involving 17,294 drivers aged 70 and older.
Researchers estimated that universal vision testing would save nearly 300 lives annually compared with not testing at all.
Eight states did not require vision tests at the time of the study: Alabama, Kentucky, Mississippi, New Jersey, Oklahoma, Tennessee, Vermont and West Virginia.
Testing motorists' road knowledge had an insignificant effect on the rate of fatal crashes involving elderly motorists, researchers said.
James T. Lang, a spokesman for the Maryland Motor Vehicle Administration (MVA), said the state requires all drivers to take vision acuity tests every five years when they renew their licenses.
Drivers aged 70 and older who apply for a Maryland license for the first time also must submit a physician's letter attesting to their medical suitability for a license.
Other proposals to tighten the licensing requirements for older drivers in Maryland have been discussed at the MVA and in the General Assembly, Mr. Lang said.
None of the proposals have become law yet.
"We know that other states place certain limits on some [elderly] drivers. They are restricted so they can't drive on busy interstates, or during certain hours of day," Mr. Lang said. "We're taking a look at what those other states do."