An empirical investigation into dual-task trade-offs while driving and dialing

Engaging in a secondary task, such as dialing a cell phone, while driving a car has been found to have a deleterious effect on driver performance. A point often overlooked though is that people can potentially vary the extent to which these two tasks are interleaved (i.e., attention can be returned to driving more or less often while dialing). To investigate this idea of strategic variability in multitasking behavior, an experiment was conducted in a driving simulator in which participants were instructed to focus on dialing as quickly as possible or on steering as safely as possible. It was found that participants drove more safely when encouraged to do so. However, driving safely necessarily brought about an increase in the total time to complete the dialing task because of frequent task interleaving. In contrast, there was a significant increase in the lateral deviation of the car from the lane centre when participants were encouraged to complete the dialing task as quickly as possible. These results suggest that contrary to existing advice, the total time that the driver is distracted is less important to safety than the strategy used for interleaving secondary and primary tasks. In particular, there may be value in designing mobile devices that facilitate short bursts of interaction for in-car use because allowing drivers to make additional glances back to the road while actively working on a concurrent secondary task might help to elevate some of the effects of distracted driving. © 2007 Duncan Brumby, Dario Salvucci, & Andrew Howes.