WE WERE ALL HORRIFIED when the 86-year-old man plowed into a farmers market near Los Angeles, killing 10 people -- and when this tragedy was followed days later by a similar accident in Florida, which fortunately didn't result in any deaths.

But the larger tragedy is what happens day in and day out, as people whose bodies or minds are no longer capable of handling the physical and mental demands of driving nonetheless continue to drive, endangering themselves and others. It's the routine wrecks, which are more deadly among older drivers than any group except the very youngest and most inexperienced.

Talk about the problem, and older drivers will latch on to the fact that teen drivers are more dangerous. That's one reason this editorial board supports tougher training requirements, higher age requirements and more stringent testing requirements for teen-agers.

But the cause of the problems are quite different. For the most part, teen drivers are immature and make bad decisions; most of them will grow out of that.

Older drivers won't grow out of the problems that plague their driving; the problems will grow worse as it becomes more difficult to crane the neck to look properly before switching lanes, as their reaction time slows, as their eyesight and hearing diminish. It is often a gradual process that is easy to miss -- particularly when you have reasons for not wanting to recognize it.

The American Medical Association recently updated its guide for doctors to evaluate older drivers, help them improve their driving and try to talk them out of driving if that is warranted. That's a smart move. But as managed care and rising costs squeeze physicians, there's only so much we can fairly ask of them. Keeping our highways safe is the responsibility of the state.

It would be ridiculous to suggest that there is some age at which people should be grounded. Some 60-year-olds are unsafe, while some 90-year-olds can still drive well. But statistics show that beginning at around age 65, the skills necessary to drive begin to deteriorate. So it makes sense to pay some extra attention to drivers as they age.

When legislators made the bad decision this year to lengthen the term of a driver's license from five to 10 years, they at least had the good sense to keep the renewal period at five years for drivers 65 and older. But that's not enough, because our renewal process is inadequate for everyone. All drivers need written tests. Older drivers need road tests as well, to help gauge their reflexes and judgment. We should consider requiring them to get a physician's approval, as we already do for people with specific physical and mental limitations, and progressively shortening the renewal time.

But this shouldn't be an all-or-nothing process. While some need to stop driving, some can still drive safely with restrictions, such as no night-time driving. Some might do fine after a course designed for older drivers.

Once we have some money, we should also consider making some changes to help older drivers. (After all, lawmakers have decided to try to lure retirees to the state.) Florida has added more and larger road signs to decrease the chance that older drivers will miss a turn; it is studying a proposal to install offset left turn lanes, so they're easier to see. Some recommend widening the lines on roads to improve visibility.

As baby boomers age, the danger of older drivers will only grow as a public health problem. We need to address the problem before we experience the large-scale tragedies that are have occurred elsewhere.