When does one become too old to drive a car? That's a question currently being pondered more and more by the families of older drivers.

Elderly drivers now account for nearly 20 percent of all motorists, according to the Government Accountability Office. And that number isn't shrinking in the coming years, because those who make up the first wave of the huge baby-boom generation turned 65 this year.

According to a recent survey from The Hartford and the Massachusetts Institute of Technology's AgeLab, almost 1-in-10 adults are now worried about an older family member's driving.

Are Older Drivers Putting Themselves (And Others) At Risk?

The data on elder-driver safety is a mixed bag. The Insurance Institute for Highway Safety reports that the nation's senior citizens are actually getting into fewer serious car accidents. Fatal crashes per licensed driver over age 70 fell 37 percent from 1997 to 2008, says the IIHS. Meanwhile, among younger drivers, fatal accidents dropped 23 percent.

But another IIHS study of intersection crashes found that 58 percent of drivers 80 and older failed to yield at intersections, while the number for drivers 70-79 was 37 percent. By comparison, 26 percent of drivers 35-54 failed to yield. "Intersections are especially challenging for the oldest drivers," said Russ Rader, an IIHS spokesperson.

The increase in the number of elderly drivers, and the accompanying concerns by loved ones, have prompted discussions by government agencies, insurance companies and university researchers about how to address this issue. The National Transportation Safety Board recently convened a two-day public forum in Washington to address the topic of America's aging population as it relates to driving.

"First and foremost, we need to recognize the mobility needs of the elderly," said Deborah Bruce, project manager for the NTSB's Office of Highway Safety and organizer of the NTSB forum. The goal of the forum was to discuss ways to prevent and reduce accidents, injuries and fatalities, and to inform the public and other federal agencies about the issue.

Having A Conversation

The American Association of Retired Persons teamed up with the MIT AgeLab -- in conjunction with The Hartford -- to produce an online course, titled "We Need to Talk." It gives family members information on the emotional connection to driving, tips on observing the driving skills of their elderly parents, and suggestions on how to broach the subject of whether or not the elderly parent's driving skills may have diminished -- and if so, when it might be time to hang up the keys.

"The number of older drivers on the road is definitely a concern, and their number can't help but increase in the years ahead, due to the aging of the population," said Lisa D'Ambrosio, a research scientist at the MIT AgeLab who helped develop the online course, as well as the original guide book that inspired it.

"We know that having that first conversation with an older parent is going to be a difficult one, because driving is so intrinsic to our sense of independence and autonomy," said D'Ambrosio. "So many of us are dependent on driving, especially in regions where public transportation does not exist, or is inconvenient, or runs irregularly. There is also a concern about what the transportation alternatives might be if an older person has to stop driving."

NTSB's Bruce added that "special-needs transportation services are inadequate to meet the current needs of the elderly, much less respond to the growing need" in the future.

Ultimately, then, the subject of whether the driving skills of the elderly have diminished may be less about driving itself -- and more about their ability to make their own decisions, and not be dependent on others.

Some of the key factors that can affect an older person's driving skills are the possibility of diminishing vision, or not being flexible enough to turn around to check blind spots, or not having the coordination or strength to adequately operate the accelerator and brake pedal.

Judging If Someone Is Fit For Driving

One way to determine whether an elder parent is having such problems is to ride with them and observe, then, based on those observations, deciding whether it is time to have "the conversation," advised Elinor Ginzler, who heads the AARP's work on health issues.

"Driving with a loved one lets you both talk from experience rather than from perception," said Ginzler. "It also gives the adult child a way to open a conversation about driving. 'Mom, I couldn't help but notice...' is a lot less alarming than, 'Mom, I want to talk with you about something.' "

Gven the sensitivity of the subject, it also might be more effective to have a progression of conversations, over time, based on those observations, as opposed to having one "big talk." It's probably best to not just start with "give up the keys," observed Ginzler.

Obviously, there is no specific age at which an older person should stop driving – it all depends on the individual, their health, and their driving skills. Driver's license renewal procedures for older drivers vary from state to state. Twenty-six states have special license-renewal requirements for senior-citizen drivers. In some states, older drivers must apply for renewal more frequently once they reach the age of 65. In others, it's 70, in others it's 72. Some states require that drivers over a certain age renew their licenses in person rather than electronically or by mail. And in some cases, road tests and/or vision tests may be required, depending on the state.

Warning Signs: 20 Things To Look For In Eldely Drivers

• Decrease in confidence while driving
• Difficulty turning to see when backing up
• Easily distracted while driving
• Other drivers often honk horns
• Hitting curbs
• Scrapes or dents on the car, mailbox or garage
• Increased agitation or irritation when driving
• Failure to notice traffic signs or important activity on the side of the road
• Trouble navigating turns
• Driving at inappropriate speeds
• Uses a "copilot"
• Bad judgment making left turns
• Delayed response to unexpected situations
• Moving into wrong lane or difficulty maintaining lane position
• Confusion at exits
• Ticketed moving violations or warnings
• Getting lost in familiar places
• Car accident
• Failure to stop at stop sign or red light
• Stopping in traffic for no apparent reason

Ranked from minor to serious. Source: IIHS

If a person's continued fitness to drive is in doubt, because of the person's appearance or demeanor at the license-renewal appointment -- or because of a history of crashes or violations, reports by physicians, police, and others -- state licensing agencies may require renewal applicants to undergo physical or mental examinations, according to the IIHS. States generally have medical review boards, consisting of health care professionals, who advise on licensing standards, and in individual cases where a person's ability to drive safely is in doubt.

"What families need to do is look for patterns of warning signs and for an increase in frequency and severity of the warning signs," said MIT's D'Ambrosio