Cellular Telephone Conversation While Driving: Effects on Driver Reaction Time and Subjective Mental Workload

The effects of conversation through a cellular telephone while driving on driver reaction time and subjective mental workload (SMWL) were investigated. Two vehicles equipped with measurement devices were used to measure reaction time. The drivers’ SMWL was measured by the National Aeronautics and Space Administration Task Load Index procedure. The experiment was conducted on an expressway in Japan. Thirty-one subjects participated in the experiment; 19 were young and 12 were elderly drivers. Each subject was asked to follow a leading vehicle and to keep a constant distance while following. The subjects performed four tasks: (a) following a leading vehicle, (b) operating a cellular telephone while following the leading vehicle, (c) performing a simple conversation task, and (d) performing a complex conversation task on a cellular telephone with the experimenter while following the leading vehicle. The results of these experiments indicated that the performance of the telephone tasks increases the reaction time and SMWL of the drivers, as was shown in a previous study. The results also indicated that the complex conversation task produced an increase in reaction time as compared to the simple conversation task, independent of age group. Furthermore, the experiment indicated that the SMWL also increased significantly in the complex conversation task as compared to the other tasks.