You might have heard this advice before, but the National Safety Council has just made it official: They call on motorists to stop using cell phones – even those with hands-free attachments – while driving. They’re also urging state governments to pass laws banning phoning and text messaging while behind the wheel. NSC President and CEO Janet Froetscher had this to say:

Driving drunk is also dangerous and against the law. When our friends have been drinking, we take the car keys away. It’s time to take the cell phone away.

Cell phones might not seem as potentially lethal as alcohol, but Salon’s Katharine Mieszkowski finds the evidence against the devices compelling:

Since cellphones started taking over the world in the ’80s, common sense has told us that people gabbing on them while driving are more likely to get into accidents than those who are not. Now the hard evidence is mounting. In 2005, an Insurance Institute for Highway Safety study found that drivers talking on the cellphone were four times more likely to get in an accident serious enough to injure themselves. That study, based on cellphone records of drivers in Western Australia, confirmed the findings of a similar study on Canadian drivers conducted back in 1997, which found drivers who were on the phone four times more likely to have a crash resulting in property damage. Neither study found any evidence that hands-free phones are safer.

There are about 42,000 traffic fatalities in the United States every year. It’s hard to pinpoint just how many crashes involve a driver using a cellphone, since reporting varies. But a 2006 study by the Virginia Tech Transportation Institute and the National Highway Traffic Safety Administration found that driver inattention is implicated in almost 80 percent of crashes and 65 percent of near crashes. The most common form of distraction: the use of cellphones. However, the study found that other forms of distraction — reaching for a falling Big Gulp, for instance — were more likely to cause a crash than chatting on the phone.

Yet the rap sheet against driving while chatting just keeps getting longer. A review of 120 studies of cellphones and driving conducted by the Insurance Institute for Highway Safety found that nearly all of the studies reported some impairment of driver performance when on the phone. That includes reacting to hazards more slowly and driving more slowly. Drivers on the phone also tend to be more herky-jerky in the movement of their steering wheel, displaying a lack of control, and have a dangerous habit of weaving out of their lanes.

The problem isn’t so much the holding of a phone (which hands-free devices address) as the inattention. Dave Munger at Cognitive Daily describes some of the studies on cell phone use and distraction, including one that found that drivers having a phone conversation were more likely to miss their exit during a driving simulation than were drivers conversing with a fellow passenger. (Adult passengers are more likely to slow a conversation when traffic conditions are difficult, and may even alert the driver to things he or she could miss.)

CDC has declared motor-vehicle safety to be one of the top ten Public Health Achievements of the 20th Century, but notes that “motor-vehicle crashes remain the leading cause of injury-related deaths in the United States, accounting for 31% of all such deaths in 1996.” It took a multi-pronged approach – including enactment and enforcement of laws, and public education campaigns – to reduce drunk driving. Convincing people to stop talking on the phone while driving may be even more challenging.