Earlier this week the United States Department of Transportation released guidelines for automakers designed to reduce the distractibility of in-vehicle technologies (e.g., navigation systems). :
The guidelines include recommendations to limit the time a driver must take his eyes off the road to perform any task to two seconds at a time and twelve seconds total.
The recommendations outlined in the guidelines are consistent with the findings of a new NHTSA naturalistic driving study, The Impact of Hand-Held and Hands-Free Cell Phone Use on Driving Performance and Safety Critical Event Risk. The study showed that visual-manual tasks associated with hand-held phones and other portable devices increased the risk of getting into a crash by three times. [emphasis added]
But a new study (I have not read the paper yet) seems to show that even when you take away the “manual” aspect through voice input, the danger is not mitigated:
The study by the Texas Transportation Institute at Texas A&M University was the first to compare voice-to-text and traditional texting on a handheld device in an actual driving environment.
“In each case, drivers took about twice as long to react as they did when they weren’t texting,” Christine Yager, who headed the study, told Reuters. “Eye contact to the roadway also decreased, no matter which texting method was used.”