For a long time, many have suspected it's unsafe to drive while talking on your cell phone. Now, researchers say they have proof that listening and looking are hard to do well at the same time.

Scientists at Johns Hopkins University in Baltimore looked at the brain patterns of people trying to do two things at once. They found that when the brain processes visual signals, there's less activity in the audio signal area of the brain -- and vice versa.

"You need to put down the phone and focus because your brain really can't do everything at once," says Johns Hopkins professor Steven Yantis. "You really are limited."

But Jim Wilson doesn't see it that way. He runs a courier service. "You pretty much have to use your car as your office," he says.

As for the extra risk Wilson takes on by multitasking, he says: "It's the cost of doing business."

It's the same for real estate agent Joanne Greater. She spends about 3,000 minutes talking on her cell phone each month, most of it while driving. Greater chose a headset model, because she believes it's both convenient and safer.

Perhaps it is more convenient, but experts say hands-free phones aren't any safer than other models. It's a message reinforced on Transport Canada's website.

Meanwhile, safety experts say there's no use in banning cell phones while driving. "The Safety Council isn't proposing or supporting laws that will have no effect at all," says Raynald Marchand of the Canada Safety Council.

Marchand says such a law is "potentially unenforceable." Instead, he says drivers should be educated about the risks of talking on cell phones while driving.

His advice is to pull over and answer the phone if you really need to. Better yet -- ignore any calls you get while driving.

With a report from CTV's Jill Macyshon