They found those drivers' reaction times were just as slow as normal texting, which was about twice as slow as driving without texting. In short, you should be cautious if you're considering leniency about hands free texting for truck drivers in your safety program. And of course, you should train your drivers to recognize when they're distracted — there are many more distractions than just cell phones in a truck cab.
Ironically, the hands-free mode (Siri for the iPhone, Vlingo for Android) made the drivers feel safer, according to the researchers.
Drivers first navigated the course without any use of cell phones. Each driver then traveled the course three more times performing a series of texting exercises, once using each of two voice-to-text applications (Siri for the iPhone and Vlingo for Android), and once texting manually. Researchers then measured the time it took each driver to complete the tasks, and also noted how long it took for the drivers to respond to a light which came on at random intervals during the exercises.
Among the major findings researchers discovered driver response times were significantly delayed no matter which texting method was used. In each case, drivers took about twice as long to react as they did when they weren’t texting. TTI says, "with slower reaction times, drivers are less able to take action in response to sudden roadway hazards, such as a swerving vehicle or a pedestrian in the street."
Previous studies have tested installed voice-to-text systems. This is one of the first studies using a hand-held device that most people have.