There is a growing literature on the factors and combinations of factors that cause secondary task interference during driving (see Horrey &Wickens, 2006; Salvucci & Taatgen, 2011). In one study, Levy et al. (2006) had college students perform two tasks simultaneously during a realistic driving simulation using the PRP procedure. In a choice task they responded either manually or vocally to the number of times (one or two) a stimulus (visual or auditory) occurred. In a braking task, they depressed a foot
pedal when a lead car also braked. The results showed that the braking task RTs increased significantly during the concurrent choice task (especially at short SOAs), showing the typical PRP effect.When participants were instructed to ignore the choice task and to give priority to the braking task, most continued to show longer braking RTs (Levy & Pashler, 2008). Clearly, even a simple and wellpracticed task such as vehicle braking is subject to dual-task interference.