The stereotype: White-haired senior citizen drivers are poking nervously along the highway, frustrating younger drivers who are in a rush to get past.
The concern: Experts predicted that crash rates would soar as America grew older.
The reality: Older people are driving more and crashing less, and their rate of fatal accidents has dropped by 37 percent.
The biggest drop of all -- 47 percent -- has come among drivers older than 80.
This all emerged in a study released this week by the Insurance Institute for Highway Safety, an industry group whose research benefits from both federal highway statistics and data collected by the companies whose policies cover the cost of accidents.
While the numbers made the trend clear, they didn't provide a solid explanation for the striking difference between what was anticipated and what came to pass. Neither could the experts who compiled the statistics.
The study compared the numbers for older drivers with those for a control group whose members were ages 35 to 54.
The older drivers did far better than the control group.
The drop in fatal accidents among the 70-and-older crowd was 14 percent steeper, and the decline in nonfatal crashes was 11 percent lower.
The Federal Highway Administration determined that between the mid-1990s and the early 2000s, the average number of miles driven by people 70 and older increased from 6,064 to 9,000 miles a year.
Part of the reason might be that more-mobile people are graduating into the ranks of the 70-and-over crowd, where the numbers holding driver's licenses swelled by almost 4 million between 1997 and 2008.
"If you think about the baby boomers and how they're changing things, maybe they're taking longer trips?" said Ann McCartt, co-author of the report. "In the past, older drivers have been less likely to drive on the interstates, even though they are safer than local roads. The baby boomers may be less reluctant to do that."