The study, conducted by researchers from the University of Utah for US consumer group AAA, found that drivers exhibit a similar level of distraction when using hands-free voice-to-text technology to send text messages as when typing texts manually with their hands.
The researchers studied 150 drivers with an average age of 24 and an average of seven years of driving experience. The participants wore brain sensors while driving a modified vehicle and were asked to perform a series of tasks, including using a hand-held phone, using voice-to-text technology and completing a test designed by psychologists to measure brain function.
The study showed drivers using voice-to-text exhibited many signs of being distracted, with reaction times as slow as drivers using a hand-held device. Drivers also made fewer head checks to observe their surroundings when using voice-to-text than in normal driving conditions.
University of Utah psychology professor and lead author of the study, David Strayer, said the research showed that “hands-free is not risk-free”.
"These new, speech-based technologies in the car can overload the driver's attention and impair their ability to drive safely," Strayer said.
"An unintended consequence of trying to make driving safer – by moving to speech-to-text in-vehicle systems – may actually overload the driver and make them less safe."
AAA president Robert Darbelnet said the future proliferation of similar in-vehicle technologies threatened a “public safety crisis”.
"It's time to consider limiting new and potentially dangerous mental distractions built into cars, particularly with the common public misperception that hands-free means risk-free."
Texting while driving is banned in the majority of US states, as well as in all Australian states and territories, though there are no laws against using voice-to-text systems.