The researchers said the reasons are not only because eyes are away from the road -- some texters, of course, can basically touch type -- but because of a shifting between the two realms of attention.

Divided Attention

The team, led by psychologists Frank Drews and Dave Strayer, has been conducting studies on driver distraction caused by cell phones and texting. The study, published in the journal Human Factors, used test subjects in a high-fidelity driving simulator.

Twenty men and 20 women, aged 19 to 23, were monitored as they either just drove or drove and texted. The researchers measured their brake onset time, following distance, lane maintenance, and collisions. The test subjects had an average of 4.75 years of driving.

The researchers reported that "drivers apparently attempt to divide attention between a phone conversation and driving," which means they are continually "adjusting the processing priority of the two activities, depending on task demands." Continually paying attention to such activities as composing, reading or receiving a text substantially lowers overall reaction times below what they might be during a phone conversation.

The result of the attention delay means that texting drivers respond more slowly when brake lights flash on the car immediately ahead, and there was impairment in forward and lateral control.

The kind of texting activity also makes a difference, the researchers found. For instance, reading a text message has a bigger effect on braking times than writing a message.

Texting Is 'Insanely Dangerous'

The researchers found that the median reaction time of drivers was 30 percent longer when texting, but only nine percent when talking on a phone, as compared to when they are only driving.

The study's findings are especially relevant as texting continues to grow. In the U.S. alone, for instance, more than one trillion text messages were transmitted last year.

Because of the dangers of texting while driving, the practice is banned in many states and cities in the U.S. Avi Greengart, an analyst with industry research firm Current Analysis, noted that "everyone in the industry acknowledges that it is insanely dangerous, if not illegal," to text while driving.

But texting is only the tip of the electronic iceberg, as cars move toward becoming mobile communication pods.

Ford has announced that the next generation of its SYNC in-car system will enable users to plug in their mobile broadband modem and turn the entire car into a moving Wi-Fi hot spot. Additionally, the company is working to open up the system so third-party applications can be downloaded. All of this will mean much more electronic activity in at least some cars -- some of which might be undertaken by drivers.