) -- Hands-free cellphone systems distract drivers almost as much as holding a device up to your ear -- and voice-to-text email programs are more or less the worst of all, AAA research shows.
"'Hands-free' is not risk free," says University of Utah researcher David Strayer, who recently studied distracted driving for AAA. "You can get impairments even with some of the new voiced-based
systems that allow you to keep your hands on the wheel and your eyes on the road."
Strayer and his team performed a series of experiments on volunteers to measure how a range of distractions -- from listening to the radio to answering math questions -- affect driving proficiency.
Using road tests and driving simulators, researchers monitored how volunteers' brake times and adherence to speed limits and proper following distances changed as subjects engaged in a series of side activities. Investigators also recorded participants' brain waves and eye and head movements to see how well drivers stayed focused on the road.
Based on the findings, Strayer created a system to rate how much different activities impair drivers.
Rankings range from a Category 1 (minimal distraction) to a Category 5, which the professor describes as "off the charts." Tasks that demand roughly the same amount of brainpower as regular driving rate a Category 1, while those involving 200% the concentration levels garner a Category 2, etc.
Strayer says anything higher than a Category 2 appears dangerous, as "you're pretty minimally engaged as a driver by the time you get above that."
Here's a look at how various activities rank on his scale:
- Regular driving. Strayer gave driving with no distractions a baseline ranking of Category 1.
- Listening to the radio. This activity also rates a Category 1, as the professor calculated it only involves 121% of regular driving's "mental workload."
- Listening to books on tape. Strayer estimates listening to books on tape requires 175% the brainpower of regular driving, meaning it's still a Category 1.
- Hands-free cellphone calls. Hands-free cell calls rank a Category 2 because they require an estimated 227% as much mental work as basic driving does.
- Talking to a passenger. Holding a conversation with another person in your car is a Category 2 task because it involves some 233% as much cognitive effort as regular driving.
- Hand-held cellphone calls. Talking on a cellphone you hold in your hand ranks a Category 2, as it demands roughly 245% the concentration that driving with no distractions does.
- Dictating an email with speech-to-text system. This activity rates a dangerous Category 3 because it involves an estimated 306% as much brainpower as driving a car with no side activities.
- Doing math/memory problems. To learn whether mental distractions impair drivers more than physical ones (such as holding a cellphone), researchers gave test subjects a series of math and memory problems to solve while traveling down the road. While drivers would never do such work in real life, Strayer ranked the tests -- which involve brainpower but no physical effort -- a Category 5 because they require an estimated 500% of simple driving's cognitive effort.
Strayer says his rankings show that laws allowing hands-free cell calls while banning hand-held ones "just aren't based on good science. They're making a distinction between two activities that seem to have the same level of impairment."
So he recommends drivers "not be lulled into thinking 'hands-free' is risk free. Driving is inherently risky -- you need to not only keep your eyes on the road and your hands on the wheel, but you need to pay attention to what you're doing."