Voices in Self-Driving Cars Should be Assertive to More Quickly Grab a Distracted Driver's Attention

Automated driving will mean that people can engage in other activities and an important concern will be how to alert the driver to critical events that require their intervention. This study evaluates how various levels of assertiveness of voice command in a semi-AV and different degrees of immersion of a non-driving task may affect people's attention on the road. In a simulated set-up, 20 participants were required to execute actions on the steering wheel when a voice command was given while playing a mobile game. Regardless of how immersed the driver was in the game, a more assertive voice resulted in faster reaction time to the instructions and was perceived as more urgent than a less assertive voice. Automotive systems should use an assertive voice to effectively grab people's attention. This is effective even when they are engaged in an immersive secondary task.