ARLINGTON, VA --- Despite growing numbers on the road, fewer older drivers died in crashes and fewer were involved in fatal collisions during 1997-2006 than in years past, a new Insurance Institute for Highway Safety study reported.

Crash deaths among drivers 70 and older fell 21 percent during the period, reversing an upward trend, even as the population of people 70 and older rose 10 percent. Compared with drivers ages 35-54, older drivers experienced much bigger declines in fatal crash involvements. Reasons for the fatality declines aren't clear, but another new IIHS study indicated that older adults increasingly self-limit driving as they age and develop physical and cognitive impairments.

Compared with drivers ages 20-69, fewer people 70 and older are licensed to drive, and they drive fewer miles per licensed driver. However, older people now hang onto their licenses longer, drive more miles, and make up a bigger proportion of the population than in past years as baby boomers age. There were more than 20 million licensed drivers 70 and older in 2006, compared with just under 18 million in 1997. The total annual miles these older drivers traveled climbed 29 percent from 1995 to 2001, compared with a 6 percent rise among 35-54 year-olds. Per mile traveled, crash rates and fatal crash rates increase starting at age 70 and rise markedly after 80.

These trends have raised concerns about older drivers in fatal crashes. Their fragility makes them vulnerable to getting hurt in a crash and then to dying from their injuries. Physical, cognitive and visual declines associated with aging may lead to increased crash risk.

Earlier research predicted that older drivers would make up a substantially larger proportion of drivers in fatal crashes, so "the findings are a welcome surprise," said Anne McCartt, the institute's senior vice president for research, and an author of the new studies. "No matter how we looked at the fatal crash data for this age group -- whether by miles driven, licensed drivers or population -- the fatal crash involvement rates for drivers 70 and older declined, and did so at a faster pace than the rates for drivers 35-54 years old."

Declines per licensed driver increased with age so that drivers 80 and older had the most dramatic decreases. If the fatal crash involvement rates for older drivers had mirrored the trend for younger ones from 1997 to 2006, nearly 7,000 additional older drivers would have been in fatal crashes (1,376 drivers 70-74 years old, 1,680 drivers 75-79, and 3,935 drivers 80 and older). Fatal crash rates fell among older drivers for most types of crashes, and the decline was dramatic for crashes at intersections.

"The large drop in intersection crashes is especially important because institute and other studies have shown that older drivers are over-represented in multiple-vehicle crashes at intersections," McCartt said. "The data don't allow us to point to any one reason why older drivers' fatal crash experience has improved. Some drivers may have benefited from newer and safer vehicles, and older people generally are more fit than in years past, with better access to health care."

Older drivers are mostly a danger to themselves. Seventy-five percent of people who die in crashes involving older drivers are these drivers themselves or their older passengers.

One way some older drivers lower their crash risk is to limit driving. A separate ongoing study by the institute is examining how older adults restrict their driving in response to declines in their health, mobility, vision and memory. Researchers recruited drivers 65 and older in three states as they renewed their licenses between November 2006 and December 2007. In the first of several planned interviews, more than nine in 10 of these drivers said that driving themselves is their primary way to travel. Fewer than 1 percent said they'd been advised by family, friends or a doctor to give up driving.

Most drivers reported at least some impairment, and the extent of impairment increased with age. For example, 26 percent of drivers 65-69 reported having at least some type of mobility issue, compared with 43 percent of drivers 80 and older. The oldest drivers were more likely to say they restricted their own driving. Drivers 80 and older were more than twice as likely as 65-69 year-olds to self-limit driving by doing such things as avoiding night driving, making fewer trips, traveling shorter distances, and avoiding interstates and driving in ice or snow.

The percentage of drivers who said they limit their driving increased with each added degree of impairment. Drivers cited memory and medical impairments more often than vision or mobility ones. For example, among drivers 80 and older, 74 percent reported medical conditions such as diabetes or arthritis. Sixty-nine percent cited some memory impairment, such as more often forgetting names and appointments or misplacing items, compared with five years ago.