Influence of mental workload on reaction time while driving a car

MAKISHITA, Hiroshi; MATSUNAGA, Katsuya · 2005 · Crossref

DOI: 10.5100/jje.41.228

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Summary

This study investigates the impact of mental workload on driver reaction times, specifically examining how secondary cognitive tasks affect hazard response across different age groups. Motivated by the prevalence of traffic accidents caused by inattention and the increasing use of in-car devices that impose cognitive loads without requiring visual distraction, the research aims to quantify these effects and determine if stationary tests can predict drivers who are significantly impaired by mental workload while driving. The experiment involved 30 male drivers divided into three age groups: young (20–29 years), middle-aged (41–54 years), and elderly (61–64 years), with 10 participants in each group. Subjects performed driving tasks on a simulated city street course. Reaction times were measured in response to a buzzer sound (2,200 Hz, 80 dB) presented while the vehicle was either stationary or moving at 50 km/h. The mental workload was induced by requiring participants to perform continuous mental arithmetic (addition problems requiring carry-over) simultaneously. The study compared reaction times under six conditions: stationary with no load, stationary with mental calculation, driving at 50 km/h with no load, driving at 50 km/h with mental calculation, and two lane-keeping tasks at 50 km/h and 30 km/h. Results indicated that mental calculations significantly increased average reaction times for all age groups. However, the effect was most pronounced in the elderly group. Statistical analysis revealed a significant interaction between mental calculation and age, showing that elderly drivers experienced a much larger increase in reaction time compared to younger drivers when performing arithmetic while driving. Furthermore, the elderly group exhibited greater individual variability and larger outliers in reaction times under high-load conditions. Crucially, the study found no statistically significant correlation between reaction times during mental calculation while driving and those during mental calculation in a stationary vehicle. This lack of correlation held true for middle-aged and elderly drivers, and was only significant for young drivers when comparing driving-with-calculation to stationary-without-load conditions. The findings suggest that mental workload disproportionately impairs the reaction capabilities of elderly drivers, highlighting the dangers of cognitive distraction for this demographic. The absence of correlation between stationary and driving conditions implies that simple stationary tests are ineffective for identifying drivers who are highly susceptible to mental workload impairments while operating a vehicle. Consequently, assessing driver safety under cognitive load requires dynamic testing environments rather than static assessments.

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Topics

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• mental demand
• cognitive capacity variation

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