It may have happened to you. You may have been driving along, maybe I-65 here in southern Indiana and you knew which exit you needed to take. But then your passenger asked you a question. Not a real difficult question, but enough to shift your focus from looking for your exit to attempting to answer their question.
Maybe it was just your child asking what was for dinner. You answered the question and they followed up with a few more. Successfully fielding those questions you return to focusing on your driving and the road ahead and suddenly you realize you just drove past your exit.
Hands-free driving, while promoted as a safer way to interact with your vehicle or your phone while in a vehicle, is apparently like that. Even after you have dictated a text or changed a radio station, your brain needs time to return to focusing on driving, and if during that time a vehicle slams on its brakes or a child darts out in front of you, the consequence can be tragic.
A study by AAA has found that some vehicles voice-activated systems could create potentially unsafe driving conditions, after studying tasks involving distractions ranging from the changing a radio station to contacting people via contact lists.
Cars tested in the study required a drivers' attention anywhere from 15 seconds to 27 seconds. The researchers noted that distraction could be increased when systems failed to understand voice commands or required many steps to complete a task.
They also noted that designing such systems should limit the tasks to driving-related items and refrain from allowing a driver to engage in tasks that really should not be done in a moving vehicle, such as updating social media.
Source: npr.org, "Even After Hanging Up, Hands-Free Isn't Risk-Free For Distracted Drivers," Kylie Mohr, October 22, 2015