For years, the common assumption has been that older drivers are unsafe drivers. But a new study from the Rand Institute for Civil Justice challenges that notion, concluding that young drivers (15 to 24) are more likely to cause accidents.

The study -- using high-quality data on counts of two-car fatal accidents involving drivers of different ages -- found that drivers 65 and older are somewhat more likely, specifically 16 percent more likely, than adult drivers (those 25 to 64) to cause an accident.  “While that difference is significant, it is perhaps far smaller than the conventional wisdom, fueled by anecdote, would imply that it would be. And it is nowhere near the risk that younger drivers pose to the public,” the study said, noting that young drivers are 188 percent more likely than adult drivers to cause a crash.

The study found that older drivers drive far less than adult drivers do, 38 percent fewer miles, while younger motorists drive about 54 percent more than adult drivers. “Together, these findings suggest that younger drivers pose a much greater risk to traffic safety than do older drivers, both because they are likelier to cause a crash and because they drive many more miles,” the study noted. It stated that older drivers, who represent 15 percent of all licensed drivers, cause 7 percent of all two-car accidents while younger drivers, who represent 13 percent of all licensed drivers, cause 43 percent of all two-car accidents.

Why?  The study suggests that many older drivers stop driving or compensate for their impairments by changing their behavior: driving less frequently, avoiding high-speed zones and eliminating night-time driving. “While driving ability declines with age for most people, those seniors who continue to drive appear to be safer drivers than the general public might think,” said David Loughran, a RAND senior economist who was the lead author of the study. “By far, it is the youngest drivers who pose the greatest risk to traffic safety."

When they do get in accidents, drivers 65 and older are at much greater risk of serious injury or death because they are generally in poorer health and more frail than younger people, according to the study. Senior drivers are nearly seven times more likely than younger drivers to be killed in a two-car accident. “Seniors who drive pose a much larger risk to themselves than to others,” Loughran said.

So what do these findings mean? For one thing, state motor vehicle departments should carefully consider the costs and benefits of imposing stricter licensing requirements on older drivers. “Our results suggest that there are relatively few older drivers who need to be legally prohibited from driving,” the study says.  Attention would be better spent on improving car safety technology, such as airbags and seat belts to reduce injuries among older people. And of course, the study adds, “more public attention should be given to reducing the riskiness of younger drivers.”