Using a cell phone while driving doesn’t just raise the risk of a car accident and injury. It can also be deadly. In fact, it is estimated that distractions contribute to about 16 percent of all fatal car crashes, leading to some 5,000 deaths every year.

According to the AAA Foundation for Traffic Safety, distracted driving is a real concern for drivers, who say other drivers’ inattention to the road makes them feel less safe.

Recent studies conducted by the AAA Foundation show that drivers are easily distracted by the following:

  • Competition for visual processing (a driver takes his eyes off the road to interact with a device).
  • Manual interference (a driver takes his hands off the steering wheel to manipulate another device).
  • Cognitive sources (a driver’s attention is withdrawn from the processing of information necessary for the safe operation of the vehicle).

These three sources of distraction can operate independently or jointly.

Participants in one of the studies operated a driving simulator on a multi-lane road with moderate traffic. The lead vehicle braked periodically, so following distance and brake reaction time was measured. Eight scenarios were examined and each task was evaluated on a scale of 1 to 5 for the level of cognitive distraction:

  1. Participant operated a simulator with no external distraction.
  2. Driver listened to the radio.
  3. Driver listened to a book on tape.
  4. Driver talked with a passenger seated next to the participant.
  5. Driver conversed on a hand-held cell phone.
  6. Driver talked on a hands-free cell phone.
  7. Driver used a speech-to-text interfaced email system.
  8. Driver was asked to complete a serious of two-step mathematical equations and told to remember a word between each problem, and at the end of the exercises, the participant had to recall the words in order.

In the first experiment, participants were asked to complete the tasks without the driving simulator. Scenarios 1, 2, and 3 rated low on the scale, while 5, 6, 7, and 8 rated the highest and most likely to case increased distraction.

In the second experiment, participants completed the same tasks while operating a driving simulator. Results showed that reaction time slowed significantly relative to the level of cognitive distraction.

Simulators were also used in a third experiment, but this time the driver had to navigate streets and cross intersections. Eye movement was measured and recorded. Participants increasingly failed to scan the road and intersections for potential hazards when completing scenarios 6,7, and 8, despite the fact that these were hands-on, eyes-on tasks.

Based on the study results, the AAA Foundation concluded that although voice interaction is hands free, it is not “brain free.” It uses a driver’s cognitive abilities, which are still needed to safely operate the vehicle. Also, when compared to other activities like listening to the radio and talking with passengers, interacting with a speech-to-text system was the most cognitively distracting behavior. This suggests that voice-based systems in vehicles may negatively impact driver and traffic safety.