Effects of Cellular Telephone Use While Driving Based on Objective and Subjective Mental Workload Assessment

Tokunaga, Roberto Abraham; Shimojo, Akihiro; Hagiwara, Toru; Kagaya, Seiichi; Uchida, Ken-etsu · 2001 · Crossref

DOI: 10.17077/drivingassessment.1019

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Summary

This paper investigates the impact of cellular telephone use on driver mental workload and reaction time, motivated by prior evidence that mobile phone usage negatively affects driving behavior and subsequent Japanese traffic law reforms. The authors conducted three distinct studies to evaluate these effects using both objective metrics (reaction time) and subjective assessments (Subjective Mental Workload, or SMWL, measured via the NASA-Task Load Index). The research aimed to determine how telephone handling methods, driver experience, and conversation complexity influence driving performance. The first study utilized a driving simulator to compare hand-held systems (HHS) and hands-free systems (HFS). Twenty-four male drivers performed various tasks, including calling, receiving, and talking. Results indicated that HHS significantly increased both reaction times and SMWL compared to HFS. Specifically, the call task with HHS yielded the longest reaction time (1.18 seconds) and highest SMWL. Drivers frequently missed visual stimuli during HHS call and receipt tasks, whereas HFS performance was comparable to baseline driving tasks. The second study was a field experiment on an expressway involving 16 male drivers, split into experienced and inexperienced groups regarding in-car phone use. Participants followed a lead vehicle while performing driving, operational, and talking tasks. The study found that experience did not improve reaction times; both groups exhibited similar delays during talking tasks. However, experience significantly affected SMWL. Inexperienced drivers reported significantly higher mental workload during operational and talking tasks, whereas experienced drivers showed little change in SMWL across tasks. This suggests that while experience reduces perceived mental strain, it does not mitigate the objective delay in reaction times. The third field experiment examined the effect of conversation complexity and age, involving 31 drivers (young and elderly groups). Participants engaged in simple and complex conversations (math problems) using HFS. Both reaction times and SMWL increased significantly during complex conversations compared to simple ones and baseline driving. This increase was consistent across both age groups, indicating that conversation complexity, rather than age, was the primary driver of increased mental workload and delayed reactions. The authors conclude that cellular telephone use while driving increases mental workload and reaction times, posing safety risks regardless of driver experience or age. While hands-free systems reduce workload compared to hand-held devices, they do not eliminate the cognitive burden, particularly during complex conversations. The findings imply that traffic safety issues related to phone use are not merely operational but stem from limitations in human information processing capacity. Consequently, improving device design alone is insufficient; the quantity and quality of information processed by the driver must also be considered to mitigate risks.

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Topics

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• mobile phones
• mental demand
• cognitive
• visual manual
• distraction laws
• temporal

Information type

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• Empirical Findings: behavioral performance data, observational prevalence
• Theoretical Contribution: theory or model