Concurrent processing of vehicle lane keeping and speech comprehension tasks.

With the growing prevalence of using in-vehicle devices and mobile devices while driving, a major concern is their impact on driving performance and safety. However, the effects of cognitive load such as conversation on driving performance are still controversial and not well understood. In this study, an experiment was conducted to investigate the concurrent performance of vehicle lane keeping and speech comprehension tasks with improved experimental control of the confounding factors identified in previous studies. The results showed that the standard deviation of lane position (SDLP) was increased when the driving speed was faster (0.30 m at 36 km/h; 0.36 m at 72 km/h). The concurrent comprehension task had no significant effect on SDLP (0.34 m on average) or the standard deviation of steering wheel angle (SDSWA; 5.20° on average). The correct rate of the comprehension task was reduced in the dual-task condition (from 93.4% to 91.3%) compared with the comprehension single-task condition. Mental workload was significantly higher in the dual-task condition compared with the single-task conditions. Implications for driving safety were discussed.