"The data and research clearly show that when drivers are not looking at the road, bad things can happen quickly," the alliance, which includes the Detroit 3 and nine other automakers, said in a statement. "We are extremely concerned that [the study] could send a misleading message since it suggests that hand-held and hands-free devices are equally risky," the group added.
Automakers have poured resources into voice-activated features in recent years, seeing them as a safer way to satisfy customers who demand nonstop access to cellphones, text messaging and social media.
For instance, Chrysler Group's Uconnect software lets drivers listen to their text messages and compose replies using voice commands. The system, supplied by Panasonic Automotive Systems Co., also lets drivers use voice commands to select a playlist on an iPod, to make a phone call or to ask for directions to an address.
Peter Fannon, vice president of technology policy at Panasonic, said the company labors to keep its products from distracting customers.
"We all know that you can be distracted by eating, or drinking, or dropping something down the side of the seat, or turning around to talk, or looking the wrong way at the wrong time," he said. "Connectivity has to take that risk into account as well. It's right at the top of the list of everyone's design criteria."
Voice controls often are packaged with infotainment systems. The number of cars sold worldwide with those systems will rise from 9 million this year to 62 million in 2018, according to a March report by consultancy ABI Research in London.