If you’re a parent who’s concerned that your teenage driver is putting herself at risk by yakking on a cell phone while barreling down the highway, here’s a zinger of a line that might finally cause her to rethink her distracted ways.

Tell your happy-go-lucky young motorist that she drives like an old lady.

Of all the admonitions available to parents of young, inexperienced drivers, telling them that engaging in phone conversations while driving puts their critical reaction time into the senior-citizen category might be just enough to chip their veneer of invincibility.

If not, hand them this column, along with their very own application for an AARP card, and let them read the eye-opening facts for themselves.

“If you put a 20-year-old driver behind the wheel with a cell phone, his reaction times are the same as a 70-year-old driver,” said David Strayer, a University of Utah psychology professor and author of a recently published study on the perils of phone-distracted driving. “It’s like instant aging.”

In fact, the research also concluded that motorists who talk on cell phones are more impaired than drunken drivers with blood alcohol levels exceeding 0.08. The study showed that it doesn’t matter whether the phone is hand-held or hands-free, in case you’re wondering. Anytime a driver is actively engaged in a phone conversation, Strayer reported, driving abilities are likely to be impaired.

The research, published in the winter issue of the journal Human Factors, revealed that when 18- to 25-year-olds were placed in a driving simulator and talked on a cell phone, their reaction times to brake lights of a car in front of them slowed to that of drivers 65 to 74 years of age who were not talking on phones.

In the simulator, each participant drove four 10-mile highway trips of about 10 minutes each. The test subjects talked on a hands-free cell phone with a research assistant for half the trip, and drove the other half without talking. The phone conversations slowed their braking time 18 percent, and it took 17 percent longer for them to regain the speed they’d lost after braking.

This is the same university research team, by the way, that determined in 2002 that cell phones can cause a troubling mental distraction in drivers called “inattention blindness,” which can seriously compromise our ability to react to unpredictable events on the road. When our brains are fully engaged in a car-phone conversation, the study showed, our eyes can look directly at something – a road sign, the brake lights ahead – and not really see it at all. In that study, drivers who chatted with passengers experienced no such mental disconnect; they simply adjusted their conversations according to the changing demands of the road.

If all this information causes young drivers to suspect a scientific conspiracy, at least older drivers can take some pride in knowing that their years on the road count for something. Elderly drivers who use cell phones, it turns out, are no more (and no less) of a hazard to themselves or others than young motorists. Researchers, who had earlier assumed that seniors would have great difficulty in dividing their attention between the road and the phone, found instead that their driving experience and tendency to take fewer risks helped to negate any additional dangers.

Not that making phone calls while driving is safe at any age. So if it suddenly dawns on you that you’ve managed to drive a couple of exits past the one you wanted, maybe it’s time to hang up and pay attention.