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Is hands-free cellphone use really safer for driving? We asked MythBusters.

Mythbusters tested the myth that it’s no safer for drivers to talk using a hands-free device than it is to drive with a handheld phone to their ear. (Video: Discovery)

Conventional wisdom — and the law in many states — says that using a Bluetooth device is safer than hands-on when using your cellphone while driving. Others contend there is no difference.

So, which is true? Well, who better to put the claim to the test than the trusted duo of debunkery: the MythBusters.

Hosts Adam Savage and Jamie Hyneman weighed the claim during an August episode of their popular Discovery Channel show. They tested the myth that it’s no safer for drivers to talk using a hands-free device than it is to drive with a handheld phone to their ear. It was part of an episode dedicated to dangerous driving, a practical topic for a show known for over-the-top demonstrations and, well, explosions.

“We get asked all the time to make the point of what the most dangerous thing we do on the show is,” said Hyneman, who once attached rockets to a car and watched it disappear in a fiery ball of smoke, in an interview. “The most dangerous stunt is on the road going to or from the actual experiment.

“You get in this metal box at these ridiculous speeds, aimed at these other metal boxes going in the other directions at similar speeds, being driven by, for all you know, crazy people,” he added. “If we were doing an experiment that required that, if not for the fact that we’re used to it, it would not pass our safety requirements.”

Cellphones, the hosts said, are an added hazard to an already-dangerous stunt. In an earlier episode, Savage performed worse in a driving test while talking hands-free on a cellphone than when the testers drove drunk. But the hosts wanted to see whether it was any safer to use a hands-free device.

“I think it’s a cultural bias that hands-free must be better,” Savage said.

All it took was an elaborate 360-degree virtual driving simulator (hooked up to a real car) at Stanford University. They populated the virtual world with hazards — pedestrians, bicycles, dogs darting into the street.

In an earlier maneuverability test, Hyneman had scored an atrocious 66 out of 100 while using a hands-free device. Savage, using a handset, scored a 73.

But the Stanford test was the one that effectively removed all doubt. Savage compared it to driving in his neighborhood in San Francisco’s Mission District.

“You’ve got cars, bikes, scooters, electric scooters, electric bikes, hipsters, dogs…probably electric hipsters,” he said.

Here’s what they found: In a simulation involving 30 drivers, exactly two managed to pass a driving test while talking on a cellphone. No surprise there.

But then it got interesting. Of the 15 drivers using handsets: one passed, five failed by driving the wrong way and nine failed by crashing.

Of the 15 talking hands-free: one passed, six failed by driving the wrong way, and eight failed by crashing.

[Watch the video here.]

The statistical difference, the MythBusters said, is negligible. It is no safer to use a hands-free device while driving than it is to use a handset.

Lest you wonder what goes on off camera in the world of TV science, Savage said the eye-opening simulator was also stomach-turning.

“Their simulator made me sick almost instantaneously,” he said. “I have a weak stomach.”

The results were definitive, the hosts said.

Of course, drivers in the District and Maryland have at least one reason to opt for a hands-free device. It’s the law.

There’s no such requirement in Virginia.

The National Safety Council says the issue is more mental than physical. Drivers talking on a cellphone, the organization says, can overlook up to 50 percent of what’s around them while looking out the windshield. And activity in the area of the brain that processes moving images is reduced by up to a third when talking or listening to the phone while driving.

The results, however, weren’t convincing enough to spur a change in habits. Adam and Jamie have busy schedules, after all, so they occasionally still commit the cardinal offense their episode aimed to discourage. And reporters, sometimes, are complicit in their behavior.

“I do all the time, even after this story,” Hyneman said, of talking on his cellphone while driving.

Disclaimer: Savage was interviewed by phone while driving down U.S. Route 101 into San Francisco. When we talked, he was about to cross the Golden Gate Bridge into the city in his Toyota Land Cruiser. “So I’m on the most beautiful stretch of highway in country,” he said. He used earbuds, which he acknowledged are no safer than a handset.