An Evaluation of the Effects of a Functional Energy Drink on Post-lunch and Early Evening Driving Performance

Parks, A. M.; Sexton, B; Burton, Sue; Hu, Henglong; Shaw, J. C. L.; Daggy, Bruce P. · 2001 · OpenAlex-citations

DOI: 10.17077/drivingassessment.1011

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Summary

This pilot study investigates whether a functional energy drink can mitigate driver fatigue and improve performance during post-lunch and early evening driving periods. Motivated by evidence that sleepiness contributes to 6–30% of road injuries, the research aimed to evaluate the drink’s effect on mental alertness and driving behavior without the ethical risks of on-road testing. The study utilized a driving simulator to provide a controlled, repeatable environment for assessing subjective fatigue, hand-eye coordination, and specific driving metrics. The experimental design involved 24 healthy participants (12 male, 12 female) in a double-blind, crossover study. Subjects consumed either a 250ml energy drink containing 75mg caffeine and 37.5g glucose, or a matched placebo, on four separate occasions. Testing occurred during two fatigue-prone periods: the post-lunch dip and the early evening. Performance was measured using the Karolinska Sleepiness Scale (KSS) for subjective fatigue, an Adaptive Tracking (AT) task for hand-eye coordination, and a 40km simulated motorway drive. The driving simulation assessed speed choice, lane-keeping accuracy, situation awareness, and reaction times in moderate traffic conditions. Results indicated that the energy drink significantly reduced self-reported sleepiness compared to the placebo, with effects lasting longer than those of the placebo. After 1.5 hours, placebo subjects showed increased fatigue, while energy drink consumers remained significantly more alert. The energy drink also significantly improved performance on the Adaptive Tracking task, particularly during the afternoon session, representing a 10% improvement over baseline. In the simulated driving task, subjects who consumed the placebo drove significantly faster in traffic during afternoon sessions (66.5 mph) compared to those who consumed the energy drink (64.3 mph). Additionally, there was a consistent trend toward better lane-keeping performance (reduced standard deviation of lane position) after consuming the energy drink, though this did not reach statistical significance. Other measures, including Useful Field of View and situation awareness, failed to discriminate between the two conditions. The study concludes that even a small volume of a formulated energy drink can effectively reduce subjective sleepiness and improve hand-eye coordination, which translates to more conservative speed choices and potentially better lane control in simulated traffic. These findings suggest that functional energy drinks may have implications for highway safety by delaying fatigue onset or reducing its behavioral effects. However, the authors note that further research is required to replicate these findings and determine the underlying mechanisms of speed selection changes, as well as to increase the sensitivity of other performance measures.

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• sleep deprivation