WASHINGTON: Speech-to-text devices in new cars fail to overcome the well-known perils of hands-on texting while driving, a US study published Wednesday suggests.

Developing standards for measuring cognitive distraction behind the wheel, University of Utah researchers wired the heads of 32 drivers with sensors, then gave them an array of tests in vehicle simulators and real automobiles. While the research is ongoing, early findings suggest that sending texts with a hands-free voice recognition system -- a feature in many new vehicles -- was more distractive than listening to the radio or conversing with passengers.

"This clearly suggests that the adoption of voice-based systems in the vehicle may have unintended consequences that adversely affect traffic safety," said the study, sponsored by the non-profit AAA Foundation. "Just because a new technology does not take the eyes off the road does not make it safe to be used while the vehicle is in motion."

The 12 men and 20 women who participated in the study ranged in age from 18 to 33. All had clean driving records -- and all confessed to regularly using their cell phones while driving.

In a report last year, the National Safety Council estimated that 24 percent of all motor vehicle crashes in the United States involve cell phone use, despite bans in several states that are openly flaunted by many motorists.