Three experiments were conducted in this simulator study to measure and understand cognitive distraction in the vehicle. In the first experiment, participants performed eight tasks; 1) a baseline single-task condition (i.e., no concurrent secondary task), 2) concurrent listening to a radio, 3) concurrent listening to a book on tape, 4) concurrent conversation with a passenger seated next to the participant, 5) concurrent conversation on a hand-held cell phone, 6) concurrent conversation on a hands-free cell phone, 7) concurrent interaction with a speech-to-text interfaced e-mail system, and 8) concurrent performance with an auditory version of the Operation Span (OSPAN) task. Those same eight tasks were completed while operating a high-fidelity driving simulator in the second experiment. The third and final experiment involved participants completing the tasks while driving the simulator on a route involving a residential section of a city.
Results revealed that there were significant impairments to driving that stem from the diversion of attention while operating the vehicle. Driving impairments were directly related to the cognitive workload of in-vehicle activities, such as listening to the radio or talking to passengers. Therefore, despite creating technologies to limit driver distraction it seems that voice-based systems in the vehicle have unintended consequences that negatively affect traffic safety.
Strayer, D. L., Cooper, J. M., Turrill, J., Coleman, J., Medeiros-Ward, N., & Biondi, F. (2013). Measuring cognitive distraction in the automobile.