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Status Report, Vol. 50, No. 2 | March 3, 2015 Subscribe

Decline in crash risk spurs better outlook for older drivers

Older drivers are more likely to crash for every mile they travel than middle-age drivers, but the overall crash outlook for older drivers has markedly improved during the past two decades. Two developments are helping lower the fatality rate among drivers age 75 and older: They are involved in fewer crashes per mile traveled, and they are surviving side impacts more often than prior generations, a new IIHS study indicates.

Prior IIHS studies have shown that older drivers have enjoyed bigger declines in fatal crash rates per licensed driver and per vehicle mile traveled than middle-age drivers since the mid-1990s (see "Fit for the road: Older drivers' crash rates continue to drop," Feb. 20, 2014). Researchers surmised then that the improvements were likely due in large part to a combination of safer vehicles and the fact that older adults are generally healthier and less fragile than prior generations.

The latest research delves further into the characteristics of the declines in older driver death rates. Using information from federal databases of fatal and police-reported crashes and of vehicle miles traveled, IIHS researchers examined how fatality rates per vehicle miles traveled for drivers age 75 and older compare with those of middle-age drivers ages 35-54 and quantified how changes in crash involvement (crash risk) and older driver survivability (death risk) contributed to changes in fatality rates from 1995-98 to 2005-08.

Compared with drivers ages 35-54, those age 75 and older experienced large declines in crash risk (police-reported crash involvements per mile traveled) and modest declines in death risk (driver deaths per police-reported crash involvement) from 1995-98 to 2005-08. Among drivers ages 75-79, crash risk declined 22 percent and death risk fell 11 percent relative to middle-age drivers. Among drivers 80 and older, crash risk dropped 31 percent and death risk fell 12 percent relative to middle-age drivers.

Drops in crash risk accounted for 68 percent and 74 percent, respectively, of the relative decline in fatalities per vehicle mile traveled among drivers 75-79 and 80 and older compared with middle-age drivers.

Many factors may have contributed to the large drop in crash risk among older drivers. One is that older adults are logging more miles than ever before. Average annual vehicle miles traveled per driver rose 60 percent for drivers 75-79 and 51 percent for drivers age 80 and older from 1995-06 to 2008. This suggests that the percentage of low-mileage drivers may have declined during the period. Low-mileage drivers tend to have higher crash rates per vehicle mile traveled, possibly because they tend to drive a larger proportion of miles on local roads with more conflict points or because they have physical or cognitive impairments that have led them to self-limit their driving.

In the IIHS study, declines in death risk among drivers age 75 and older, relative to middle-age drivers, were much larger in side crashes than in front crashes (18 percent versus 5 percent).

"This is a good example of how changes in vehicle safety initiated many years ago are affecting crash outcomes today," says Jessica Cicchino, a senior research scientist at IIHS and the study's author. "Improvements in side impact protection are helping older drivers walk away from crashes that might have killed their parents or grandparents."

Airbags designed to deploy in side crashes and certain offset frontal ones have been standard on the majority of new vehicles since the 2008 model year. There is evidence that side airbags are more effective in preventing fatalities among front-seat occupants ages 70-96 than among those ages 13-49, while front airbags have equally benefited both demographics.

Older drivers also appear to be benefiting from vehicle designs that minimize the harm larger, heavier vehicles can inflict on smaller, lighter ones in crashes (see "Better compatibility has lessened the danger that SUVs and pickups pose to people in cars," Sept. 28, 2011).

"Safer vehicles are leveling the playing field, but older adults' fragility is still a big threat when it comes to surviving crashes, especially for drivers 75 and older. That physical vulnerability continues to be the leading contributor to older drivers' fatality rates," Cicchino says.

Fragility accounted for 77 percent of the elevated fatality rates for drivers ages 75-79 and 68 percent for drivers 80 and older relative to middle-age drivers during 2005-08, the study found.

SIDEBAR
Intersections challenge older drivers

Older drivers look but don't always see potential conflicts when they travel through intersections, especially when turning left.

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