SAN FRANCISCO - It was a baby-boomer anthem: having fun, fun, fun 'til Daddy takes the T-Bird away. But as car-crazy boomers age into grandparents, the question is becoming: when to take Daddy's license away.
At the American Gerontological Society's annual meeting this weekend, and around the country, experts are trying to figure out how to get unsafe older drivers off the road without unfairly penalizing those who drive well.
Statistics show that drivers over 65, along with teen-agers, have the highest accident rates per miles driven. But proposals in several states to toughen requirements for older drivers have been thwarted recently by senior-citizen lobbying groups who say age-based measures are discriminatory.
''There are good drivers and bad drivers of all ages,'' said Nina Glasgow, a Cornell University researcher who opposes age-based testing and favors screening targeted at all unsafe drivers.
Several states require elderly drivers to renew their licenses more frequently than other drivers, but very few require road tests or medical exams.
Lawrence Nitz, a political scientist from the University of Hawaii, presented a three-year study of Hawaiian traffic records at the gerontological meeting. It found that drivers over 75 were far more likely than other motorists to be cited for certain offenses, including failing to yield to pedestrians, backing up unsafely and failing to stop at a flashing red light.
To deal with elderly problem drivers, Nitz suggested a phased removal of driving privileges comparable to the phased adding of privileges for young drivers. For example, an older driver might be barred from driving at night or restricted to an area near home.
Other experts argued that most elderly drivers regulate themselves effectively, knowing when to avoid nighttime or highway driving. Some cautioned that any extra push to get older drivers off the roads could have negative effects - isolating residents in areas without good public transit and reducing their independence.
Glasgow said her research has shown that elderly drivers are more likely to participate in club and church activities than non-drivers.
''There's a risk to ceasing driving,'' she said. ''People who have stopped driving tend to have lower morale.''
Anita Myers of the University of Waterloo in Ontario, Canada, said her province had a stringent license-renewal policy dating to 1936. Drivers over 80 must renew their licenses every two years and take a 90-minute driver education class.
Myers surveyed elderly drivers about the procedure and found them generally tolerant. The mandatory class drew high marks, she said: ''They loved the defensive driving tips.''
Road tests were part of Ontario's renewal requirements until 1996, but the tests are now required only for selected drivers with questionable safety records.
With the number of elderly drivers increasing rapidly across the continent, it becomes less and less feasible for authorities to institute mandatory road tests on any broad basis.
As an alternative, experts are seeking quicker, cheaper ways to identify high-risk drivers. A major study is taking place in Maryland, monitoring vision, alertness and reflexes among more than 2,000 volunteer older drivers in hopes of developing effective and relatively simple screening procedures.
Legislative efforts to toughen requirements in Oregon and California failed this year following lobbying against the bills by the American Association of Retired People.
The Oregon bill would have required drivers over 80 to renew their licenses every two years, instead of four, and to take driving and medical tests.
In California, state Sen. Tom Hayden abandoned an attempt to require road tests for drivers over 75 when it become clear in September that his measure lacked the needed votes.
''It's discriminatory to base mandatory testing on the fact that someone has achieved a birthday,'' said Helen Savage, one of the AARP lobbyists who fought the bill.