Makers of cars and mobile electronics are pushing a tempting vision of the future, one in which you can stay fully connected while driving. In the name of safety, they provide hands-free wireless setups for your cellphone, so you can talk with both hands on the wheel. The latest additions are voice-to-text systems that let drivers send and receive texts and emails without looking at a screen. Some high-end cars even have touch screens with interfaces for finding restaurants, reserving tables and buying movie tickets while on the road.

Has all this made the impulse to stay connected while driving any safer? According to a new study, definitely not.

The study, conducted by University of Utah psychologist David Strayer and sponsored by the AAA Foundation for Traffic Safety, compared driver response in different situations. Listening to the radio or audiobooks was judged mildly distracting. Talking on a hand-held or hands-free phone or to a passenger was more distracting, with hand-held conversations the worst of these. But voice-activated systems to send and receive texts and email were the worst kind of distraction.

The fundamental problem is that safe driving demands attention, but multitasking divides our mental resources. "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," Strayer said.

His data show that talking to the voice-to-text system is more cognitively demanding than talking to a person, leaving less brainpower for driving.

The National Highway Traffic Safety Administration says distracted drivers killed more than 3,300 people in the United States in 2011. In April, the agency recommended that manual text entry and the display of text messages or Web content be blocked in all moving vehicles.