UNIVERSAL CITY, Calif. (AP) _ They usually wear seat belts, almost never speed and rarely drink and drive. Yet elderly drivers, among the most responsible in the nation, often end up in crashes.

It's a disturbing mystery that has researchers turning to a virtual reality road test for answers.

The test devised by University of Maryland scientists puts seniors in front of a computer screen, where they ``drive'' through a cartoon scene.

Cars cut across the street, pedestrians appear suddenly and stop signs and trees flash by. Sometimes the image flickers, disrupting the way the driver's eyes and brain perceive changes.

From the simulation, scientists hope to develop a research model of how brain and motor skills work together. The goal is to devise driver training and engineering designs to improve road safety.

``For the elderly, the key is preventing the crash in the first place because they don't survive,'' said Charles Fox, assistant professor of ophthalmology at the university.

The test was discussed Sunday during a seminar sponsored by Research to Prevent Blindness, a voluntary organization that supports eye research.

Fatal accidents among the elderly have increased 25 percent over the past decade, Fox said, while the rate for another at-risk group, teen-agers, has fallen. And those 65 and older will account for nearly one-third of the nation's drivers by the year 2000.

The seminar focused on the aging eye and on treating diseases that can rob older Americans of their ability to see _ and drive.

``We're trying to break down the system to find where the weak spots are,'' said Fox, who is also a behavioral neuroscientist. ``I believe that crashes occur when the drivers misjudge their ability to adapt to their changing abilities to perceive speed and distance.''

Nissan Car Corp. research scientists in Boston, who are collaborating on the project, could one day use the research to design cars with special features to help seniors, Fox said.

In other research discussed Sunday, preliminary results from a Maryland study indicated sunlight exposure increases the incidence of cataracts in older people.

The results, based on a study of older residents of Salisbury, Md., indicate that for every 1 percent increase in the amount of ultraviolet-B rays that reach the eye, there is a 10 percent increase in cataracts, or clouding of the lens of the eye.

No figures were given for the number of cataracts found. The study was based on the average annual exposure of the eye to the damaging rays.

Researchers also said experimental treatments are showing early promise against the so-called ``wet'' form of age-related macular degeneration.

Some 70,000 to 200,000 Americans each year suffer from the disease in which excess blood vessels develop in the back of the eye behind the macula _ the area used for reading and recognizing faces _ then leak and starve the light-sensing part of the eye.

The treatments include radiation to destroy the leaky vessels; injecting light-sensitive dye into target cells and then using laser light to kill them; and surgically shifting the macula a few millimeters away from the damaged region to restore sight.