I know people over here who think that they are fine talking on the phone while driving as long as it is hands-free; they have a 'belief' that it is not slowing down their reactions. With this type of person you'd need to take them on a course and demonstrate to them how it's adversely effecting their reaction time.
"Vision is the most important sense for safe driving. Yet, drivers using hands-free phones (and those using handheld phones) have a tendency to ?look at? but not ?see? objects. Estimates indicate that drivers using cell phones look but fail to see up to 50 percent of the information in their driving environment.Distracted drivers experience what researchers call inattention blindness, similar to that of tunnel vision. Drivers are looking out the windshield, but they do not process everything in the roadway environment that they must know to effectively monitor their surroundings, seek and identify potential hazards, and respond to unexpected situations."
http://www.nsc.org/safety_road/Distr...5-25-10%29.pdf