Researchers studying driving habits and accident rates among the elderly found a majority surveyed supported mandatory（强制的） retesting of drivers based on age while saying they would hand over the keys if a doctor or loved one said they were no longer fit to drive. "We are now exploring the idea of an advance directive for driving where someone would be designated to take away your keys at some point," said Emmy Betz, MD, MPH, at the University of Colorado School of Medicine who led the study and presented it in May before the American Society of Geriatrics. "It is a very difficult subject. Children don't want to bring it up, older drivers are afraid to lose their licenses and doctors may not feel it is not their job."

The study surveyed 122 elderly people and found 71 percent supported mandatory, age-based driver retesting. It also showed that 68 percent believed family and 53 percent believed doctors should decide whether a license should be revoked（撤销，取回） . Only 28 percent said the Department of Motor Vehicles and 26 percent said the police should make that decision.

Some 89 percent said they might quit driving if their doctor advised it compared to 75 percent who would agree if it was their family's idea. Twelve percent reported a crash in the last year and 87 percent of current drivers said they had at least one medical diagnosis possibly linked to increased crash risk. The elderly drivers also reported taking a median（中值的） of seven medications each.

Betz, an associate professor of emergency medicine, said the problem is growing as more and more baby boomers retire. Still, she said, despite sensational stories of the elderly crashing into crowds or running people down, drivers over age 75 are responsible for only four percent of pedestrian（徒步的） fatalities. But older drivers do have high motor vehicle accidents per miles driven with less ability to recover from injuries due to their often frail condition.

"We are trying to develop a screening test to identify higher risk drivers," she said. "The tool is a simple questionnaire with questions like, `Do you get confused by driving? Do people recommend you stop driving?'"

If someone is deemed unsafe to drive, Betz said, the question is who should notify the Department of Motor Vehicles - doctors, family or both?

"This is where the advance driving directive could come in," Betz said. "We would have something in writing that says when the time comes who do you trust to make the decision that you can no longer safely drive?"

Each state has its own method of determining whether elderly drivers are competent, most include a vision test. Betz, who recently received a Merck/American Geriatrics Society Young Investigator award, said there is more to it than that.

"It is not all about vision. There are complications from diabetes that may affect driving, cognitive problems – does a person forget how to make a left turn? – and dementia（痴呆） which may develop in some at age 60 and others at 90," she said. "The drugs they may be taking could also have side-effects that impact driving ability. Ultimately, this is a public health issue that needs to be addressed in a coherent（连贯的） way involving family, doctors and state authorities."