right of the roadway, respectively. On hearing the appropriate cue, subjects: (a) switched their attention from the driving task to one of the two number streams, hereafter referred to as the primary switch; then (b) switched their attention from the first number stream to the second, hereafter referred to as the secondary switch; and finally, (c) reported the first perceived digit in each of the two number streams, respectively. Conceivably, primary switching time, as suggested earlier, could be attenuated by switching attention before the appropriate cue is presented. Secondary switching time, however, should not be influenced by this strategy and thus is not contingent on such extraneous factors.
Moreover, in this study the driving task was more challenging and perhaps more realistic. First, subjects were required to modulate their speed via the accelerator and brake pedals. Second, all overtaking maneuvers were performed on curves, rather than straights.
Nonetheless, these amendments did not modify the pattern of results. In particular, switching time was faster in the dual-task condition vis-à-vis the single-task condition, F(1, 22) = 6.95, p < .05. Moreover, switching time did not vary across road-element type, F(3, 66) = 2.01, p > .05. Finally, the effect of driving on switching time did not vary with experience; that is, the interaction between age and condition was not significant, F(1, 22) = 2.35, p > .05. Hence, the results of the present study cannot be ascribed to premature switching. In addition, the original findings generalize to more demanding conditions.
In summary, the present study showed that switching time while operating a vehicle is a positive function of age, but independent of driving experience per se. Moreover, the driving task expedited, rather than retarded, switching time. These results discredit the notion that switching time is a positive function of mental workload, and thus, are encouraging for IVHS being used by younger drivers. In particular, any additional tasks required by a high technology system should not, according to the present results, retard switching time. Although these systems may increase the required rate of switching, and thus influence complex driving performance, they should not differentially disadvantage young drivers.
The present study, however, entails several limitations. First, these findings may not generalize to real-world driving. Second, the present study examined only one aspect of switching, namely, switching between spatial locations. Other forms of switching, such as switching from one cognitive process to another, may yield conflicting results.