Hands-free but not Eyes-free: A Usability Evaluation of Siri while Driving

Distractions while driving are a major cause of traffic accidents and chief among these is the use of mobile phones. Driver distractions typically fall into four categories-visual, cognitive, bio-mechanical, and auditory-and different technological solutions have been proposed to address these. Intelligent Personal Assistants (IPAs), such as Siri, is a recent example of such a technological solution that offers the potential for hands-free phone interaction through a voice-controlled interface. IPAs could potentially reduce visual and bio-mechanical distractions if they are usable enough to not increase a driver's cognitive load. We present the results of a controlled experiment with the aim of understanding how the use of Siri while driving compares to manual interaction in terms of usability and distractions. We also tested these two interaction types in the lab in order to understand how the main driving task influences Siri's (perceived) usability. Our study shows that Siri is not ready for every-day use in the car: interacting with Siri while driving is likely to be unsafe for most participants, especially less experienced drivers. Participants were distracted by Siri due to its over-reliance on visual feedback as well as frequent time-outs by Siri when waiting for a response from a driver occupied with the road environment. Speech recognition quality in a noisy car as well as problematic multi-lingual speech recognition in general are other issues that resulted in low usability and more cognitive distractions. While interacting with Siri may be hands-free, it does not provide an eyes-free and distraction-free experience yet.