Remember "The Little Old Lady from Pasadena"? Baby boomers who first danced to that 1964 pop hit about a granny burning up the road in her hot rod will begin turning 65 in January. Experts say keeping those drivers safe and mobile is a challenge with profound implications.

The National Transportation Safety Board is holding two-day forum beginning Tuesday to better understand the safety risks that older drivers face.

Within 15 years more than one in five licensed drivers will be 65 or older, the safety board said. Their number will nearly double, from 30 million today to about 57 million in 2030, according to the Government Accountability Office.

Smarter cars and better designed roads may help keep them stay behind the wheel longer.

But eventually most people will outlive their driving ability _ men by an average of six years and women by an average of 10 years. And since fewer Americans relocate when they retire, many of them probably will continue to live in suburban homes.

The result is a "mobility gap," said Joseph Coughlin, head of the Massachusetts Institute of Technology's AgeLab, which develops technologies aimed at keeping older people active.

"For many, our homes will not be just a place to age, it will also be house arrest," said Coughlin.

Older drivers who are healthy aren't necessarily any less safe than younger drivers. But many older drivers are likely to have age-related medical conditions that can affect their driving.

A 40-year-old needs 20 times more light to see at night to see than a 20-year-old, Coughlin said. Older drivers generally are less able to judge speed and distances, their reflexes are slower, they may be more easily confused and they're less flexible, which affects their ability to turn so that they can look to the side or behind them.

Fatal crash rates for older drivers compared with other age groups begin to increase starting at about age 75, according to the Insurance Institute for Highway Safety. Drivers over age 85 have a worse fatality rate than teenagers and drivers in their early 20s.

The main reason is that older drivers are more frail and less likely to survive an accident or recover from injuries, according to the institute. Older drivers primarily kill themselves in crashes, with these accounting for 61 percent of deaths in accidents involving drivers 70 and older. Sixteen percent of the deaths were their passengers.

Many older drivers compensate for the erosion of their driving abilities by changing their driving habits.

"I'm never in a rush," said Grace M. Sanders, 87, a retired secretary in Atlanta. She takes care to map out a route in her mind before she leaves the house. She avoids driving near construction sites. If it's raining, she stays home.

But even though she could take the bus, it's important to Sanders that she keep her car.

"I always wanted to be an independent person and I maintained that independence throughout my life," she said.

New technologies, some of them borrowed from the military and commercial aviation, may help older drivers stay behind the wheel longer, and more safely. Crash warning systems using sensors embedded in the car can alert drivers to an impending accident. They can even override the driver and apply the brake. Similar technology can parallel park the car. Night vision systems can help with one of the most frustrating problems for older drivers.

Not every remedy involves new technology. Sometimes it's just a matter of making dials larger so they're easier for drivers to find. A strap can be added to hold onto when getting in and out of a car. An extended mirror can help drivers avoid turning around as much.

"They may extend the driving careers of some seniors, but they are certainly not a panacea," cautioned Dr. Bonnie Dobbs, a gerontology professor at the University of Alberta. She notes that many technologies could distract or confuse older drivers, which could lead to accidents.

Better designed roads may also help. For example, traffic "roundabouts" that gently ease drivers into turn circles with no traffic lights could help reduce left turn-related crashes, which make up a disproportionate share of the accidents that kill older drivers.

What's not being addressed is how to keep older Americans mobile after they lose their driving skills, said University of Arizona professor Sandra Rosenbloom, an authority on the transportation implications of trends such as an aging population.

"As people get older and lose the ability to drive, they narrow and narrow their circle of friends and their circle of activities until it gets to the point where they are housebound and they don't move at all," Rosenbloom said.

Public transportation _ buses and trains _ isn't a realistic option for most people who have lost the ability to drive, Rosenbloom said. By the time that happens, the physical and mental conditions that made driving untenable are also likely preclude hiking to a bus stop, especially if there's no bench. The act of getting on and off a bus can be prohibitive. Many older people _ especially those over 80 _ also worry about losing their balance on a bus and fear being victimized.

Marcia Savarese, 73, began driving when she was 16. In 2008, she suffered a stroke and didn't drive for a year. Instead, she depended on friends, expensive taxis and delivery services.

Now, she's back on the road despite a loss of some of her peripheral vision. To compensate, she said she's trained herself to turn around to look more than before. She rarely drives at night, and she stays off the interstate. She does much of her grocery shopping and other errands early in the morning when parking lots are nearly empty. Rarely does she drive more than a few miles from home.

"I feel it is safer for other people if I stay right in the local area that I know," said Savarese, a widow and retired estate jewelry dealer in Vienna, Va. She didn't want to move from her neighborhood, where she has lived for the past 40 years.

"I'm more comfortable here," she said. "My friends are here, my doctors are here, everything is here."

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Online:

National Transportation Safety Board: http://www.ntsb.gov

(This version CORRECTS Corrects 'sports car' to 'hot rod' in first paragraph and clarifies one in five licensed drivers 'within 15 years' instead of 'soon.' Forum begins at 9 a.m. EST.)