"Because of the potential for driver distraction, safety should be of great concern," Ian Spence in the Department of Psychology at the University of Toronto said.
Canadian telecommunications company Rogers Communications had announced the plans for in-car WiFi, along with U.S. provider Sprint Corp.
"Many people assume that talking to a voice-operated device will be as safe as using a hands-free cellphone, but neither activity is safe," said Spence, author of a study on the impact of auditory distractions on visual attention.
In experiments, subjects who completed a test of visual attention coupled with listening/speaking tasks were as accurate as those who completed the visual test in silence, the researchers said, but they responded much more slowly as the difficulty increased -- as much as one second slower with the most demanding tasks.
"At 50 kilometers per hour [31 mph], a car travels 13.9 meters [45 feet] in one second," Spence said. "A driver who brakes one second earlier than another driver to avoid a collision, will either prevent it completely or be traveling more slowly when it occurs, lowering the probability of severe injury or fatality.
"It did not matter whether the subject spoke the answer aloud or simply thought about the answer," Spence said. "It was the thinking, not speaking, that caused them to slow down."