Auditory alerts for in-vehicle information systems: the effects of temporal conflict and sound parameters on driver attitudes and performance

In-vehicle information systems will soon confront drivers with an increasing number of warnings and alerts for situations ranging from imminent collisions to the arrival of e-mail messages. Coordinating these alerts can ensure that they enhance rather than degrade driving safety. Two experiments examined how temporal conflict and sound parameters affect driver performance and acceptance. The temporal conflict of an e-mail alert occurring 300 ms before a collision warning interfered with the response to the collision warning, but an e-mail alert occurring 1000 ms before the collision warning had the opposite effect and enhanced the response to the collision warning. These results emphasize the need to consider how in-vehicle devices influence drivers' strategic anticipation of high-demand situations. Regarding sound parameters, results showed that highly urgent sounds tended to speed drivers' accelerator release, but the annoyance associated with highly urgent sounds increased workload. In fact, there was a strong positive association between ratings of annoyance and subjective workload. Consistent with the urgency mapping principle, there was a slight negative association between the differences in the rated urgency of collision warnings and e-mail alerts and subjective workload. The results suggest that warning and alert design should consider an annoyance trade-off in addition to urgency mapping.